خالد عبدالحسين جبير الفرحاني

The present work deals with the thermal characteristics of a single cylinder 4-stroke diesel engine powered by regular diesel, 20% biodiesel derived from green spirulina algae, and 20% biogas, which are examined numerically using Diesel-RK software. The multi-zone combustion model is used, which treats each zone as an open thermodynamic system. In addition to neat diesel, the biodiesel is blended with conventional diesel and supplied to the engine. Another fuel is the 20% biogas is used as a dual fuel. As gas fuel 20% based on an energy basis. A combination of diesel, biodiesel, and biogas is called hybrid fuel. The outcomes revealed that peak pressures and heat release rates were decreased. Sauter mean diameter reduces by 16.2% and 15% for 20% biogas and hybrid forms, respectively. There is a slight reduction in brake thermal efficiency for all tested fuels. Using 20% biodiesel reported a lower increase in brake-specific fuel consumption by 3.1% compared to 8.3% and 5.3% in the case of 20% biogas and hybrid mode, respectively. The operation with 20% biogas, 20% biodiesel, and hybrid forms reduces NOX by 27.9%, 16.6%, and 8.45%, respectively. It can be observed that the utilized of 20% biogas or 20% biodiesel separately is preferable to use rather than combining them in hybrid mode. Other researchers' findings validate the results.

The work aims to investigate the MHD Casson fluid flow over an exponentially long sheet via a thermally stratified permeable medium. All facets of chemical processes, Joule heating, and exponential heat sources are covered in this subject. By using the appropriate similarity conversions, the leading partial differential equations (PDEs) of the model are transformed into a set of nonlinear ordinary differential equations (ODEs). The description of the previous technique was made simpler by applying the Keller Box methodology. The results reveal that when the viscosity factor is increased, the velocity profile improves, but when the thermal profile improves, the opposite trending impact is evident. The temperature profile exhibits the opposite tendency, despite a decline in the number of observations of the Casson fluid constraint. Joule heating parameters allow for more precise measurements of the heat source's properties by raising the temperature. The concentration graph shows a reduction as the number of observations for the chemical reaction parameter increases. The validity of the problem is investigated by computing the Nusselt number for cumulative Prandtl number observations and comparing the results with the literature.

This paper investigates numerically the effect of MHD and entropy generation on double-diffusive combined convection in an inclined enclosure filled with Si2O/H2O and heated fins. The geometry's base is connected to double fins with three locations in three cases. A range of variables has been considered, such as Reynolds, Richardson, Lewis, bouancy ratio, the volume fraction, Hartmann numbers, and the orientation of the enclosure, to investigate how these variables can affect the fluid flow and the mass and thermal transfer. The finite element method has been applied to solve these variables, and the main findings indicated that the value of average Nusselt and Sherwood numbers increases with the increase of volume fraction, Richardson, and Lewis numbers while decreasing with the increase of magnetic strength, Hartmann number. Where Nuavg and Shavg increase to 65% and 19% when increasing Re from 40 to 180 while both values decrease to around 35% when increasing Haatmann number from 0 to 62. Moreover, increasing the volume concentration from 0 to 0.08 increases Nuavg and Shavg to around 3% and 12% respectively. Furthermore, the average Sherwood number increases with the increase in inclination angle. In contrast, the average Nusselt decreases with the increase in the inclination angle, except for the right angle, which gives a higher value. Moreover, the total average entropy generation is reduced with the increase of the magnetohydrodynamic and buoyancy ratio while increasing with the rise of Reynolds, Richardson, Lewis, and the concentration of the nanoparticles. Also, the lowest values of entropy generation are generated in Case 3, while CaseI generates the highest values of entropy generation.

In the global pursuit of sustainable urban energy solutions, urban centers' significant contributions to energy consumption and carbon emissions have driven cities to adopt energy efficiency policies and renewable resources. Archimedes spiral wind turbines (ASWTs) offer promising technology due to their spiral blade design, which ensures high efficiency at low to medium wind speeds, automatic wind direction alignment, and low noise emissions. This paper provides a comprehensive review and critical analysis of aerodynamic performance enhancement techniques for ASWTs, identifying key research gaps and suggesting future research directions. These include investigating the synergistic relationships of key blade dimensions such as diameter, length, and blade angle, concurrent with the development of more efficient augmentation systems, and improving advanced materials used to increase durability and reduce solidity. The analysis also compares previous methodologies and offers guidance on integrating ASWTs effectively within urban areas, contributing to cleaner and more sustainable energy solutions.

This study describes a computational model that simulates the behaviour of a solar-powered desalination system. The model incorporates photovoltaic/thermal (PVT) collectors and direct contact membrane distillation (DCMD). A novel DCMD unit model was established and verified using existing data from the literature and the model was incorporated into the TRNSYS library. The effect of feed water mass flow rate and temperature on production was investigated through a parametric analysis. The PVT-DCMD system was modeled, analyzed, and dynamically simulated for the month of June in Algeria using TRNSYS software. Results show that the PVT collector's outlet solar fluid temperature ranges from 20 °C to 85 °C, providing 5000 kJ/hr of useful energy for seawater desalination through a heat exchanger. Meanwhile, the auxiliary heater utilizes around 10,000 kJ/hr of solar energy. The simulation demonstrates the feasibility and effectiveness of using PVT collectors with a DCMD system for seawater desalination, achieving a distillate production rate of approximately 12 L/hr.m2 of membrane.

In this study, an experimental investigation of natural convection in a rectangular cavity filled with (CuO-Al2O3)/water hybrid nanofluid in a rectangular cavity. The rectangular cavity consists of two opposite vertical heated walls at varying temperatures. Three different mixing of hybrid nanofluid have been studied to select the best kind of hybrid nanofluid ((30%CuO-70%Al2O3), (40%CuO-60%Al2O3), and (50%CuO-50%Al2O3))/water. The concentration of hybrid nanomaterial used Φ=0.03%, and the difference of temperatures on vertical sides ΔT=5, 10, and 15 ◦C are taken into account. The results showed that the best heat transfer occurs with (50%CuO-50%Al2O3)/water.

This work numerically explores the mixed convective heat transfer in an open square enclosure containing conducting fins fixed to the heated vertical wall. This kind of work with fins has enormous potential due to its applications in research, engineering, and current industries. Therefore, the current work is highly significant to understand the impact of mixed convection. The external flow enters from the hole in the bottom wall and leaves from the hole in the upper wall. The left vertical wall of the enclosure is heated isothermally, and the fins are attached to the heated walls at a uniform height. Both the upper and lower walls are adiabatic, whereas the right sidewall is at a lower temperature. The non-dimensional transport equations are resolved by using the finite element method. The study is accomplished for the wide control variables range, such as Reynolds number (50 ≤ Re ≤ 200), Richardson's number (0.1 ≤ Ri ≤ 10), the length of the fins (Lf = 0.2, 0.4, and 0.6), the size of the outlet opening (Wout = 0.1, 0.2, and 0.3), and the gaps in between the outlet hole and left heated wall (S = 0, 0.45, and 0.9). The results show that the thermal performance of the open enclosure is meaningfully affected by the control parameters. The maximum and minimum heat transfer happens when the position of the outlet opening is at the left (S = 0) and right (S = 0.9), respectively. The heat transfer improves by raising the Ri and Re, whereas increasing the fin's length and distance between the outlet opening and left wall reduces heat transfer significantly. The rises 13% with a decrease in the fin's length from 0.6 to 0.2 at Re = 200, S = 0 due to the improvement of the convection on the heated wall. Also, increases by 15% when Ri increases from 1 to 9.

A 2-D steady-state laminar natural convective flow due to buoyancy force around a concentric adiabatic cylinder placed inside a porous trapezoidal enclosure was analyzed numerically. The slanted solid boundaries of the trapezium were subjected to a fixed cold temperature (Tc), while the base of the model experienced a hot fixed temperature (Th) and its upper wall was insulated thermally. The relevant dimensionless transport equations were solved using the COMSOL Multiphysics 5.6. Computations were performed for ,, and cylinder aspect ratio, . Isothermal and stream function plots were used to present the temperature and velocity profiles in the domain. Local and average values of the Nusselt number were used to assess the heat transfer rates from the base wall of the model. Furthermore, the vertical mid-plane velocity in the enclosure was also assessed. The analysis shows that the range of Darcy and Rayleigh numbers investigated resulted in heat transport enhancement. Furthermore, the average Nusselt number was enhanced for and . However, for , heat transfer became independent of the nature of the working fluid used and for this range of Darcy number, cylinder size increase yielded heat transfer benefits for . This research finds applications in drying technology, nuclear reactors, and the design of aero and automotive engines.

The main objective of this work is to investigate numerically double-diffusive mixed convection flow in a channel filled with a hybrid nanofluid of Cu-Al2O3 in a porous media. It is considered that the cavity's left wall is continuously heated. The fluid flow enters the channel at low concentration and temperature. This work has been looked into two cases: Case 1, where it is supposed that the left wall cavity has high concentrations, and Case 2, where it is expected that the right wall cavity has high concentrations. The cavity's remaining walls are impermeable and thermally insulated. Non-dimension governing equations are solved with the finite element method. Parameters effects of Reynolds number(10≤Re≤100), Richardson number (2≤Ri≤10), Darcy number (Da=10-2,10-4), Lewis number (1≤Le≤5), buoyancy ratio, N=1, the solid volume fraction (ϕ=0.02), and Prandtl number (Pr=6.2). The results show that increasing Reynolds, Richardson, and Darcy numbers increases the average Nusselt while it decreases by increasing Lewis number. In addition, Sherwood numbers increase with increasing Reynolds, Lewis, and Darcy numbers while they decrease with Richardson numbers for both cases. When the Reynolds number increases from 10 to 50 at (Da=10-4) and (Ri =10), the Nusselt number increases by 102%, while the Sherwood number decreases to 72%.

The purpose of the current study is to evaluate the impact of using beef Tallow methyl ester blends on the thermal parameters of diesel engine numerically utilizing Diesel-RK simulation software. The multizone combustion model is used and the governing equations are solved for each independent zone. The engine characteristics were examined under three different volumetric blends of Tallow methyl ester (10 %, 20 % and 30 %) in addition to plain diesel case for comparison. The obtained results showed slight reduction in pressure, heat release for all blends of Tallow methyl ester with respect to diesel fuel alone. The Sauter mean diameter of the droplets was increased by 1.68 %, 3.34 % and 5 % for 10 %, 20 % and 30 % Tallow methyl ester respectively. The higher tallow methyl ester ‘s cetane number is responsible for shorter ignition delay which in turn makes the combustion starts earlier. The brake specific fuel consumption increased 1.68 %, 3.34 % and 5 % for 10 %, 20 % and 30 % Tallow methyl ester respectively due to the difference of density, viscosity and energy contents. Noticeable reduction in the Bosch Smoke Number as the use of 20 % TME and 30 % Tallow methyl ester reported reduction of 13.25 % and 17.8 % while the Particulate Matter is dropped significantly by 11.1 %, 12.9 %, 18.4 % correspond to 10 %, 20 %, and 30 % percentages of Tallow methyl ester biodiesel. The plenty of oxygen quantity in Tallow methyl ester biodiesel leads to emit more Nitrogen oxides relative to diesel. Base on the results obtained, 20 % TME is best compromised blend that can recommended to be used in diesel engine without any modification of the engine. The current findings matched well with the different scientists’ results.

Numerical investigation of mixed convective in a vented square cavity with fin. The horizontal walls are adiabatic, while the left and right walls are at hot and cold temperatures, respectively. The fluid inlet to the cavity from the lower left open area, and exit from the upper right open area. In this study, a finite element scheme is employed. The analysis is done for specific Prandtl number, Reynolds number, fin length, Richardson number, and the location of the fin. The finding indicates that the increases when high the location of the fin is, the increase at the maximum height of this fin location is estimated to be 17% due to an increase in the area of fluid flow on the hot wall caused by rising convective. The highest heat transfer occurs when the fin length is equal to 0.6 at the location.

The potential of hybrid nanofluids to boost thermal efficiency of heat exchanger systems is the focus of this review study. The primary focus is on addressing the associated issues of nanoparticle clumping, system obstruction, and reduced efficacy of heat exchanger due to increased fluid thickness. Accordingly, this review intends to demonstrate the innovative practices (experimentally and theoretically) that helps improving the heat transfer and thermal performance of heat exchangers. In this regard, a critical analysis is conducted to appraise the experimental and numerical simulations, which introduce the impact of different nanoparticle concentrations and compositions on heat exchanger thermal performance. The findings of this review has shown that the hybrid nanofluid of CuO–Cu/water has the greatest thermal performance factor (1.065), following Al2O3–Cu/water (1.055), and Cu–TiO2/water (1.039). Also, the utilization of turbulator heat exchangers has enabled improving the thermal performance by 126 % with a 6 % rise in volume fraction at the maximum Reynolds number. This study underlines the need for further research into novel nanomaterial combinations, fine-tuning of fluid characteristic, and comprehensive stability assessments to enhance the utilization of hybrid nanofluids in heat exchanger systems. Finally, discussions of limitations associated with such systems and proposed potential solutions will lead to a valuable contribution in the possible future development of cost-effective heat exchanger systems.

The magnetohydrodynamic conjugate heat transfer characteristics of a ferrofluid-filled porous inclined enclosure heated differentially have been investigated numerically in the present work. Two-conducting fins are attached to the hot wall of the cavity and the horizontal walls are insulated. The ranges of dimensionless flow controlling parameters are taken as: modified Rayleigh number (10 ≤ Ra⁎ ≤ 104), length of the fins (a = 0.3, 0.5, 0.7), gap between the two fins (b = 0.3, 0.5, 0.7), and Darcy number (10−5 ≤ Da ≤ 10−2), volume fractions of nanoparticles (0 ≤ ϕ ≤ 0.06), Hartmann number (0 ≤ Ha ≤ 50), and the cavity inclination angles (0 ≤ γ ≤ 90o). The finite element method has been used to solve the governing equations and the present code have been validated with previously published work. The results show that the average Nusselt number increases by increasing the modified Rayleigh number, Darcy number, fins length while it decreases by increasing the Hartmann number. For any range of modified Rayleigh numbers, the highest fin length and the widest gap between the fins can be a superior heating strategy. At a fixed fin length, the lower gap between the fins is of a better choice to boost heat transfer when the cavity inclination angle increases up to 30o.

This study involves the evaluation of the thermal characteristics of gasoline engines fuelled with LPG instead of gasoline fuel using the simulation software Diesel-RK. The feasibility of using LPG is investigated via parameters (combustion, performance, and emissions) at different engine speeds and compression ratios. A two-zone combustion model is used. The results revealed that the maximum pressure obtained was 82 bar for gasoline compared to 78 bar for LPG at 5000 rpm. There is a noticeable reduction in BSFC with the use of LPG relative to gasoline for all ranges of compression ratio and engine speed used. The NOx emissions were significantly reduced by 8.60% using LPG rather than gasoline. Studies conducted by different researchers validate the obtained results.

This work investigates the dynamics of the hybrid nanofluidic convective heat transfer in a permeable thermal system under the influence of multifrequency heating and a magnetic field. The geometry comprises a wavy-walled cavity filled with a water-based hybrid nanoliquid (Al2O3–Cu–H2O) in a saturated porous medium. The finite volume approach is applied to scrutinize the hydro-thermal characteristics resulting from bottom heating and side cooling, considering various flow-controlling parameters. The analysis reveals that nonuniform multi-frequency heating can be a highly effective strategy for enhancing heat transfer in complex geometries involving porous systems, nanofluid flow, and magnetic fields. Significant heat transfer improvement is observed at higher frequencies, with an increase of approximately 261.49 % when offset temperatures are introduced. Additionally, an increase in the undulation height of the wavy sidewalls contributes to a partial heat transfer improvement of 13.41 % compared to the case without undulations. The influence of the Darcy number, Hartmann number, porosity index, and nanoparticle concentration on heat transfer performance is also investigated. Higher Darcy and Hartmann numbers result in reduced thermal convection, while increased porosity enhances thermal convection. Elevated nanoparticle concentrations weaken the flow strength due to higher viscosity. System engineers can optimize heat transfer systems in their respective applications by comprehending the interactions between these flow-controlling parameters. This work contributes to a deeper understanding of the hydro-thermal phenomena in a multiphysics problem and provides a foundation for the development of more efficient heat transfer systems.

This work has numerically investigated the double diffusion of free convection in a curvilinear enclosure filled with nanoliquid and containing fins with heat generation/absorption. The considered enclosure, the curvilinear cavity, has triple fins connected to the inclined walls, which are hot and have a high intensity of solutal; however, the top wall is cold and low intensity of solutal. The bottom walls, as well as the vertical walls, are considered to be isotopically insulated. The parameters that are considered are Rayleigh (from 103 to 105), Hartmann (from 0 to 60), heat generation/absorption, q, (− 4 to 3), bouncy ratio (N =  − 4 to 4), Lewis number (Le = 0.5–10), volume concentration (Φ = 0–0.06) at fixed Prandtl number. The governing equations have been numerically solved and applying the FEM technique. The important findings explain how heat and mass transfer can be improved by increasing the value of Ra, q, and Φ while decreasing with the increase in Ha. Also, the rise of the N ratio and Le number until (N = 2), where the reduction value reaches 44% from (N =  − 4) to (N = 2) at (Le = 0.5), and the effect of both N and Le become negligible for (N > 2). Furthermore, the value of Shavg has the same behaviour as Nuavg with N, where Shavg decreases with increasing N and increases with increasing Le, where maximum mass transfer enhancement reaches 65% at N =  − 4. The effects of N and Le become negligible at N = 2.

This study focuses on a numerical investigation of mixed convection heat transport in a square cavity filled with air as a working fluid. The left and right sidewalls are kept at cold temperatures, while the horizontal walls are adiabatic. A thin baffle was fixed on the adiabatic bottom wall at variable lengths. The finite element technique is used to solve non-dimensions governing equations. Parameters effects of Reynolds number (100 ≤ Re ≤ 1000), baffle length (Lb=0.2, 0.4, and 0.6), Richardson number (1<Ri<7), and Prandtl number (Pr=0.7). The results show that heat transfer increases with an increase in Reynolds number. The average Nusselt number increases as the Reynolds number increases, and the maximum value reaches when Re =1000. The findings demonstrate that the length of the baffle does not significantly affect the rate of heat transfer when Reynolds and Richardson’s numbers rise, convection overtakes conduction as the major mode of heat transfer.

This study is inspired by the emerging importance of micropolar fluids in a variety of scientific and technical fields due to varied uses and effective thermal activities. Potential applications of these fluids include cancer treatment, magnetic refrigeration, drug delivery and magnetic resonance imaging. Hall and ion repercussions on unstable magneto micropolar liquid beyond a stretched sheet are described in this article. By using the bvp4c, the resulting non-sequential coupled PDEs are transfigured into a system of coupled non-consecutive ODEs, which are remedied by a numerical procedure. An impact of various governing non-dimensional factors on velocity, angular momentum, temperature, concentration, wall friction, couple stress, local Nusselt and Sherwood numbers, is indicated graphically. The main finding specifies that Hall and Ion impacts influence velocity and with increased Hall and Ion effects, velocity raised as well as thermal boundary layer reduced. When compared to previous findings in the literature, the current findings indicate a splendid agreement. The predominant uses of this issue are in solar cell systems, such as solar water pumps, manufacturing and production processes, motion in plasmas, furnace design, nuclear power plants, and solar aircraft wings.

This investigation used the Diesel-RK simulation program to carry out a numerical analysis of the effects that dual-fuel mixes have on the combustion, performance, and emissions of a dual-fuel diesel engine. It applied the multizone combustion model, and the controlling equations were solved for each individual combustion region. The engine characteristics were examined under the following scenario: it was initially powered by single-fuel regular diesel (DF), then it switched to dual-fuel use with 20% biogas, and then it was changed again with the use of 30% dimethyl ether (DME). On this basis, the mentioned biogas and DME ratios were used. The results showed that combustion pressure for the operation of 30% DME and 20% biogas was reduced by 2.45% and 9.57%, respectively, with respect to diesel fuel alone. The Sauter mean diameter (SMD) of the droplets was reduced by 12.6% for 30% DME and 16.2% for 20% biogas. Heat release and brake thermal efficacy (BTE) were reduced slightly with the use of biogas or DME in comparison with DF. The brake-specific fuel consumption (BSFC) increased by 15.27% and 8.34%, with 30% DME and 20% biogas respectively due to the difference in the energy content of the tested fuels. Nitrogen oxide emissions decreased by 2% and 28% for the operation of 30% DME and 20% biogas, respectively. The summary emission equation (SE), which describes the combination of NOx and PM emissions, decreased by 4.23% and 5.40% with 30% DME and 20% biogas respectively. Based on the results, this paper recommends the use of 20% biogas with diesel rather than 30% DME. The current findings matched well with other scientists' results.

The current study investigates the influence of MHD on the natural heat transfer considering the irreversibility in a complex-shaped cavity with the existence of inner roundish heater with four attached fins utilizing finite element formulation. Three different cases are considered to figure out the major characteristics of temperature, stream function and total generated entropy, Nusselt number in addition to Bejan number. Concentrated attention is directed to the enclosure geometry modifications and the varied length of attached fins and their impacts. The parameters of study are ranged as follows; Rayleigh number , Hartmann number , fins’ length . The novelty of the present work is on studying all of these parameters in the complex enclosure considering three different cases of the shape of the outer walls so that the star-shaped enclosure is classified as case 1. With increasing the length that separated between the outer arc of the star enclosure, the octagonal-shaped enclosure will appear as denoted in case 2 and 3. It had been seen that at low Rayleigh number , case one is the best choice in heat transfer bettering while it is the lowest case at high Rayleigh number . Additionally, the influence of Hartmann number on the total entropy generation reduction percentage for case three is while it is 51.11% for case two while Hartmann number had negligible impact of entropy generation reduction for case one. Lastly, the highest Bejan number is at fin length is recorded for case one.

Convective flowing and heat transference of non-Newtonian liquid comprising nano-encapsulated phase-changing material (NEPCM) suspensions, filled in a square cavity, is numerically investigated. The molecules of NEPCM are cored with n-octadecane, shelled by polymethyl-methacrylate, and suspended in non-Newtonian fluid. The enclosure is insulated horizontally and heated vertically. Finite element method (FEM) is implemented for the numerical solution under different variables such as nanoparticles volume fraction (0<∅<0.0⁢5 ), Stefan number (Ste=0.2,0.3⁢1⁢3,0.5 ), the heat capacity ratio (𝜆 ) of about (0.4), the temperature of fusion of the NEPCM (0<𝜃𝑓<1 ) and the density ratio (𝜌𝑃∕𝜌𝑓 ) (0.7<𝜌𝑃∕𝜌𝑓≤0.9 ). The results show that the Nusselt quantity is related to the fusion temperature. An improvement in heat transference is observed when the fusion temperature deviates from the wall temperature, which is in the range of 0.2⁢5<𝜃𝑓<0.7⁢5 . For all power law index values (n), a linear increase of the Nusselt number with the solid volume fraction is detected. The shear-thinning nanofluid (𝑛=0.6 ) demonstrates higher Nusselt number values than those of 𝑛=1 and 1.4.

In this paper, magnetohydrodynamics of a Casson fluid flow is inspected with the presence of thermal radiation and chemical reaction. Employing the perturbation procedure, the modeling equations are tenacious; the graphs are acquired to illustrate the results. The Casson fluid velocity increases as the perturbation parameter increases. Grashof values for heat and mass transport enhanced Casson fluid velocity. Increasing Casson, magnetic, heat source, and radiation parameters reduce the flow velocity. Prandtl number, heat source, and radiation parameter all reduced the temperature profiles. Chemical reaction parameters lowered the concentration profiles. The skin friction enhances with Casson parameter impact. However, the skin-friction coefficient, Sherwood and Nusselt numbers reduce with an increment in the perturbation parameter. In certain cases, this study’s answers agreed well with the previous literature. Casson liquid with a magnetic region using mixed convection by an exponential vertical boundary layer is the novelty of the work.

The ever-increasing need for energy, along with diminishing petroleum supplies, has prompted the quest for renewable and sustainable alternative fuels. The goal of this research is to investigate theoretically the impact of using HHO gas on single-cylinder diesel engine characteristics using the simulation software diesel-RK model. Diesel fuel blended with 10% HHO gas is used and tested under different engine speeds. When 10% HHO gas was put into the engine, the thermal efficiency climbed to 31.5 percent and consequently, fuel consumption is reduced by up to 20 percent. The maximum reduction in BSN is 25% which is witnessed at 3500 rpm. The findings are corroborated by the findings of other studies. Among the most important outcomes that were obtained the peak combustion pressure was raised by 10% as compared to diesel fuel without HHO and the brake power enhances from (9% to 16%) when the engine speed is increased from (1500 to 3500) rpm.

This study investigates the possible impact of rapeseed methyl ester (RME) biofuel, caster methyl ester biofuel (CME), and engine speed on the performance, combustion, and emission of a multi-cylinder turbocharged direct injection diesel engine with high compression ratio numerically. According to the numerical simulation results, biofuel reduces the peak cylinder pressure closer to the top dead centre than that of diesel fuel. Because they used more brake-specific fuel (BSFC), both of the biofuels used had less stopping power than diesel fuel. The amount of NOx dropped by 50% when RME was used instead of DF. In the case of CME, 19% less smoke was made, but in the case of RME, only 15% less smoke was made. When RME and CME are used instead of DF, the Sauter mean diameter (SMD) goes up. The ID is shorter when biofuel is used because of the change in the cetane number. Because of the drop, biofuel starts to burn (SOC) faster than DF. As the engine speed goes from 1000 to 4000 rpm, the peak pressure goes up while the SMD goes down. There is a small difference between the findings and what other experts have found.

The current research numerically investigated the inclined magnetic field effects on the combined forced and natural convection in lid driven curvilinear cavity filled with Cu-H2O nanoliquid and a partial porous layer. The complex cavity is partially filled with a porous layer about the lower half and heated with a constant heat source. The entire cavity is occupied with Cu-water nanoliquid. The upper horizontal wall is at a cold temperature and moving towards the right with a constant velocity. The geometry is subjected to an inclined magnetic field. The derived mathematical models are computed numerically using the FEM-based tool. The thermal behavior is assessed through a range of variables, such as Richardson number (0.1 to 10), Darcy number (10 -5 to 10 -1), Reynolds number (30 to 200), Hartmann number (0 to 60), γ (0 to 60°), and nanoparticle concentration ϕ (0.0 to 0.06) at constant Prandtl number, Pr = 6.2, and porosity, ε = 0.4. The main findings indicate that heat transfer inside the cavity rise with the increase of Ri, Re, ϕ, and Da numbers, while decreasing with the rise of the MHD strength. Also, at a low Reynolds number, Re = 30, the value of Nuavg only increased by 18% with the increases in Ri number from 0.1 to 10; however, the increase in Nuavg increased to 64% with a high Reynolds number, Re = 200.

This paper numerically investigates mixed convective heat transfer in a vented square cavity incorporated with a baffle that is subjected to external non-Newtonian fluids (NNFs). Adiabatic conditions are imposed on the top and bottom walls, while cold temperature conditions are applied to the right and left solid boundaries. Heated NNF enters the cavity through the inlet and goes out through the outlet at three different locations, and it passes on a vertical baffle fixed at the base placed at different lengths. To examine the impact of the inlet and outlet positions, three different shapes of the outlet port located on the right wall and the inlet port on the left bottom wall were investigated. The impacts of Reynolds number (Re) of 100 ≤ Re ≤ 1000, Richardson number (Ri) of 0.1 ≤ Ri ≤ 3, power law index (n) of 0.6 ≤ n ≤ 1.4, length of baffle (Lb) of 0.2 ≤ Lb ≤ 0.6 and the outlet hole positions (S) of

The objective of this study is to examine the impact of multifuel blends on combustion parameters of single-cylinder four-stroke direct injection diesel engines. Engine characteristics (performance, combustion, and emissions) are scanned under the following scenario: initially powered by regular diesel (DF), then 20% biodiesel derived from spirulina green algae. Afterward, 40% water ammonia solution (25% NH3) is used, followed by a hybrid blend (40% DF + 20% biodiesel + 40% NH4OH). Simulations are performed using Diesel-RK software. In contrast to diesel and biodiesel, aqueous ammonia solution has a longer delay period due to lower cetane number. In comparison with diesel, the Sauter mean diameter (SMD) is increased by 1.6%, 3.8% for biodiesel and NH4OH, while it is decreased by 13% for hybrid fuel. Peak values of pressure and temperature are reduced. All fuel blends under consideration had significant reductions in nitrogen oxides (NOx) and Bosch smoke number (BSN). Hybrid fuel reduced NOx emissions by 37% and BSN by 53.5% compared to DF. Compared to DF, there was a slight increase in brake-specific fuel consumption (BSFC) coupled with a decrease in thermal brake efficiency (BTE). The optimal fuel compromise for dual-fuel diesel engines is the usage of biodiesel and aqueous ammonia together (hybrid mode). There is an excellent convergence between these outcomes and those of other scientists.

Natural convection in a square porous container full of Fe3O4/water nanofluid and having a wavy wall is studied numerically. The wavy wall is hot, whereas the remainder of the bottom surface are adiabatic. The left and right sides are thermally insulated; however, the top wall is cold. For modelling porous media with nanofluid, the Darcy-Brinkman-Forchheimer model was considered. The governing equations have been solved by using finite element methods. The non-dimensional parameters which were used in this work are Rayleigh number (Ra=104 to106), Darcy number (Da=10−2), number of waves (N=1, 3, 5, and 7), porosity (ε=0.6), volume fraction (ϕ=0.05), and Prandtl number (Pr=7.2). Heat transfer rises as the Ra increases, but it decreases as the number of waves increases. It has been concluded at Ra=106, and N=1 the enhancement of heat transfer is maximum and the maximum Nusselt number on the wavy wall is equal to 6.643 while the minimum Nusselt number is 0.1336 at Ra=103, and N=7.

Mechanical agitation is a fundamental unit operation required in many industrial fields such as the chemical and pharmaceutical industry, petroleum, gas dispersion, emulsification, etc. A CFD software (COMSOL Multiphysics 5.4) was applied to investigate the mixing operation of viscous fluid inside stirred tank system in this paper. The influence of introducing a new design of the Rushton turbine on the hydrodynamic behavior inside the stirred tank has been analyzed. The modification to the Rushton turbine standard is made by modifying the shapes of the blades. Four geometry designs of Rushton turbine are investigated named; RTS (Rushton turbine standard shape), RTC (turbine Rushton with circle blade shape), RTC-C (Rushton turbine with the cut circular shape), and RTC-C (Rushton turbine with the cut rectangular shape). The flow pattern, power consumption, and pumping capacity inside the vessel were investigated for different geometry configurations and Reynolds numbers. The results obtained show that there is an increase in the pumping rate (Nq) and reducing energy consumed (Np) inside a stirred tank with an improvement of flow filed (radial and axial velocities). The RTC geometry configuration is more effective than all geometry configurations studied.

An investigation of the dispersion of pollutants ejected from a chimney around a three-dimensional cylindrical obstacle within a crossflow air stream was conducted in this paper. The dynamic evolution of air seeded with glycerin particles ejected from an elevated jet around the isolated obstacle in a wind tunnel was experimentally studied using the particle image velocimetry technique and under different velocity ratios between the chimney ejection and the wind source. The dispersion of CO2 pollutant around the cylindrical building was numerically predicted based on measured experimental data using the finite volume method and the Reynolds stress model. A good agreement between experimental and computational results was found. Velocity, temperature, and concentration results revealed that the velocity of the wind together with the presence of the isolated building obstacle influenced the flow structure.

A numerical study of mixed convective heat transfer in a lid-driven square enclosure containing a hot elliptic cylinder is conducted. The impacts of the Grashof number , Reynolds number , cylinder tilt angle , and aspect ratio have been examined for a fluid of of 0.71. The horizontal enclosure walls are insulated, while its vertical walls are restricted to a nonvarying temperature Tc, whereas a sinusoidal temperature of is imposed on the wall of the elliptical cylinder. The governing equations are solved using COMSOL Multiphysics 5.6 software. The fluid dynamic and the heat transport profiles between the enclosure and the elliptical cylinder walls are represented by the stream function, isothermal contours, and average Nusselt number. Results established that for all the considered aspect ratios, the thermal heating range of is predominantly a conduction mechanism. The critical position of the ellipse where the inclination effect becomes insignificant is determined by the Grashof number and aspect ratio when the Re = 100. The strength of vortices and cell numbers are significantly influenced by the aspect ratio, particularly when the . When , the average heat transfer from the cylinder remains the same regardless of the cylinder's orientation. The impact of cylinder orientation on heat transfer from the cylinder wall is minimal for . For AR values of , increasing the inclination angle does not result in improved heat transfer. The influence of the increasing inclination angle on the right wall diminishes as the angle increases, except when the Grashof number is greater than 105, where the rate of heat transfer is enhanced for inclination angles beyond 45°.

Numerical investigation for the steady-state laminar nanofluid 2D natural convection in a partially heated porous cavity equipped with two fins at the hot wall under the effect of a uniform magnetic field is carried out. Effects of wide ranges of variables including: Hartman number (0−80), direction of the magnetic field (0o−90°), Rayleigh number (103−106), Darcy number (10–2−10–5), nano-solid particles volume fraction (ϕ = 0% and 6%), length of the attached hot fins (0.25, 0.5, and 0.75) and the length of the partially heated (0.25, 0.5, and 0.6) wall are analyzed. The study results show that by increasing the Hartman number, the average Nusselt number will decrease. Moreover, by increasing the nano-solid particle volume fraction, Rayleigh number, Darcy number, the length of the hot fins, and the partially heated wall, a better heat transfer rate is achieved; consequently, the average Nusselt number will increase. Results show no consistent trend for the effect of the magnetic field direction on the average Nusselt number. The results show an enhancement in the average Nusselt number by 22.46% in the case of b = 0.6 and ϕ = 0.06 compared to the base case of b = 0.25 and ϕ = 0.06.

This work numerically analyzes the mixed convective double diffusion of Fe3O4-water-based nanofluid in a tilt curvilinear lid-driven cavity studied under the effect of an inclined magnetic field. The horizontal upper wall is at a lower thermal and concentration gradient and moves toward the right. The side vertical walls and bottom walls kept adiabatic. Furthermore, two numbers of conducting fins are affixed to the inclined walls at high temperatures and concentrations. The finite element approach is implemented to analyze the considered variables: Richardson number (Ri), Hartmann number (Ha), Reynolds number (Re), Lewis number (Le), buoyancy ratio (N), magnetic inclination angle (α), nanofluid volume fraction (ϕ) as well as the fins length on the heat and mass transport phenomena. The results showed that the Nuavg and Shavg increase by increasing Reynolds number, the nanoparticles volume concentration, and the fin length, while they decrease by increasing Hartmann number. When Ri is small, Nuavg rises with the increasing magnetic field inclination, but when Ri is high, the inclination angle works adversely. On the other hand, the Shavg increases with the rise of the magnetic field inclination for all Ri values. It can be seen also, when Lewis number increases, the Nuavg and Shavg values increase with increasing Ri and magnetic inclination angles.

In magnetohydrodynamics (MHD) flowing and mass transfer, 2-D unsteady non-Newtonian liquid flow across the stretched surface with a surface temperature had been examined numerically. Casson fluid model was utilized for the full description of the non-Newtonian fluid. Similarity transformation had been considered for transforming the dimensionless heat and fluid flow basic partial differential equations into simple ordinary equations. After that, the bvp4c MATLAB solver utilizes numerical methods to resolve the altered equations. We study and discuss in depth the flowing and heating attributes under various parameters, including the magnetic, Casson, and unsteadiness parameters, Schmidt number, and Prandtl number. It has been proven numerically that the velocity of the fluid first reduces when temperature and unsteadiness parameters increase, which significantly negatively impacts concentration. The velocity field is suppressed when the Casson parameter’s values are increased. But when with the increment of the Casson variable, then, the concentration and temperature go up. The velocity field is suppressed as the magnetic parameter’s values increase. But with the rise in the magnetic parameter, there will be an improvement in both the temperature and concentration.

In high-performance thermal systems, convective heat transport is a critical phenomenon for sustainable operation from an energy efficiency standpoint. This study examines the convective heat transport dynamics of a hybrid nanofluid (aluminum oxide-copper–water nanofluid) under spatially varying nonuniform temperature conditions within a porous thermal system in the presence of a magnetizing field. The flow domain experiences nonuniform heating (following a half-sinusoidal profile) from both sidewalls and is cooled from the top, while the lower wall remains adiabatic. The flow domain is filled with a porous substance and a hybrid nanoliquid. The non-dimensional governing equations are derived and numerically solved using a finite volume method-based solver. To accurately capture thermal behavior, available experimental data on hybrid nanofluid thermophysical properties are utilized. The study analyzes significant control variables such as half-sinusoidal heating amplitude, frequency, and offset temperature, as well as flow control variables such as Darcy number (Da), modified-Rayleigh number (Ram), and Hartmann number (Ha). The analysis shows that non-uniform heating consistently enhances transfer by up to approximately 722% compared to uniform heating. The three temperature-controlling parameters (amplitude, frequency, and offset temperature) play a crucial role in enhanced heat transfer, and the higher their magnitudes, the higher the heat transfer. Heat flow dynamics between the heat source and the heat sink are well visualized through heat function and heatlines. Heat transfer is an increasing function of Ram and frequency, which is opposite to the rising Da or Ha. An optimum frequency at which thermal convection is maximum is about 70 for the considered range of Ram. Furthermore, mathematical correlations that combine control variables are developed for predicting heat transfer characteristics.

With the assistance of Diesel-RK software, the volumetric replacement of aqueous ammonia (NH4OH) with original diesel is being investigated in a dual-fuel diesel engine. Three volumetric percentages of ammonia solution are used along with diesel according to the scenario: (40% NH4OH + 60% Diesel), (50% NH4OH + 50% diesel), and (60% NH4OH + 40% diesel). The numerical analysis is based on a multizone combustion model. In the zone-based approach, the governing equations for each zone are solved as open systems. Comparing diesel fuel with ammonia solutions, the results show that adding ammonia solutions decreases combustion pressure and heat release and increases Sauter diameter and ignition delay. Generally, the use of aqueous ammonia drops engine performance regardless of the percentage of NH4OH used. Since 40%, 50%, and 60% of NH4OH have lower heating values than diesel, BSFC is reduced by 7.15, 10.4%, and 15.38%, respectively. Since the addition of ammonia reduces combustion temperature significantly, a noticeable reduction in NOx emissions is achieved, reaching up to 61.75% in the case of 60% NH4OH. The results highlighted a remarkable reduction in soot emissions (43.4% for 40% NH4OH, 51.04% for 50% NH4OH, and 49% for 60% NH4OH) because the diesel was replaced with no carbon fuel, hence the engine produced less smoke compared to with the baseline case (pure diesel).

he natural convective Cu-water nanofluid flow in l-shape cavity with an oscillating temperature profile is studied numerically. The cavity's lower horizontal and left vertical walls are heated sinusoidally with time about a high mean temperature ( ). In contrast, the cavity's right vertical wall and its nearby horizontal lower wall are kept cold at a temperature (Tc). The calculations have been performed over temperature oscillation amplitude ( , dimensionless temperature oscillation frequency , Rayleigh number ( , Hartmann number ( ), the nanoparticles volume fraction ), and enclosure aspect ratios ( ). Outcomes reveal that with AR = 0.2, heat transfer happens considerably through conduction at Ra = 103 –105, while the time average Nusselt number ( ) is independent of both Ha and Ra. Convection effects, on the other hand, become significant at high Ra. Additionally, as Ha ascends from 0 to 50, increases linearly with increasing ϕ, while it remains steady at Ha = 75 and 100.

This paper presents the effects of aspect ratio (0.1≤𝐴⁢𝑅≤0.7), Rayleigh number (102≤𝑅⁢𝑎≤106) and inclination angle 0° ≤𝛾 ≤ 90° of the heated rectangular cylinder on heat transfer and fluid flow characteristics due to natural convection in air around heated rectangular cylinders of different sizes inside a cold square enclosure. Galerkin finite element method was adopted for the solution of the developed model. The walls of the enclosure were maintained at an isothermal cold temperature while the boundaries of the rectangular cylinder were kept at a constant hot temperature. The results are presented in the form of isothermal contours, stream functions, local and average Nusselt numbers. It has been found that for the range of aspect ratio and Rayleigh number considered, the rate of heat transfer increases with increasing aspect ratio and Rayleigh number. Furthermore, the orientation angle of the rectangular cylinder was found to generally augment heat transfer rate except at 𝐴⁢𝑅 value of 0.1, where the average Nusselt number declines beyond 𝛾 = 45° for all the range of Rayleigh numbers considered. Results from the present study could be applied to nuclear reactor technology and cooling of electronic chips system optimisation.

An empirical evaluation of free convective heat transmission was conducted in a rectangular enclosure containing a hybrid nanofluid of (50% CuO-50% Al2O3)/water linked to a PCM-containing wall. The enclosure's left and right surfaces were kept at constant warm and cold temperatures, whereas the remaining surfaces were assumed to be isolated. The left side was filled partially with PCM. Several variables were examined, such as the hot-side temperature differential (∆T =10, 15,20 ◦C) and the hybrid nanofluid concentration (Φ=0.03,0.05,0.07)%. The findings show that the rate of heat transmission through natural convection rises as the concentration of nanomaterials rises. Due to its great absorbability and heat storage capacity, PCM was also shown to have the potential to lower the hot side temperature by up to 15.5%. The Nusselt number rises over time as the left cavity is filled partially with PCM. When added hybrid nanofluid is, PCM’s heat-storage efficiency and, by extension, its ability to cool the hot side is greatly improved.

This study addresses /CMC-water hybridnano-liquid in the influence of mixed convection flow and thermal radiative flow past a stretchable vertical surface. Cross nanofluid containing Titanium dioxide and Copper Oxide are scattered in a base fluid of kind CMC water. In addition, theirreversibility analysis is also examined in the current problem. A suitable transformation is utilized to transmute the momentum and thermal mathematical expression in non-dimensionless form. Further, the BVP utilizer is set to solve these mathematical expressions. The significance of leading variables on the velocity, entropy generation,temperature, and Bejan numberare displayed and elaborated through the aid ofgraphs. The outcomes demonstrate that the larger values of the Weissenberg number reduce the velocity and entropy profiles while escalatingthe temperature distribution and Bejan number. The drag friction and heat transfer rate are enhanced by exceeding the value of the mixed convective parameter and Biot number. The motive of this manuscript is to give more interest of entropy production study with heat and fluid flow on Cross fluid with nanoparticles and base fluid to develop the system performance. The current work is existed with the previous literaure and obtain a fantastic achievement.

Several industrial fields require mixing and mechanical agitation processes. This operation is mainly used to enhance heat and mass transfer inside stirred tank systems and improve the degree of homogeneity to obtain a high-quality final product. The main goal of this research paper is to analyze the thermal and hydrodynamic behavior of non-Newtonian nanofluid (Bingham–Papanastasiou–Al2O3) inside a symmetrically stirred tank. A 3D numerical study has been conducted for a stationary laminar flow inside a symmetric cylindrical vessel under influencing parameters, including the inertia parameter (𝑅𝑒=1, 20, 100 ) and the volume fraction of nanoparticles (Ø=0.02, 0.06, 0.1 ) with different geometric configurations, has been introduced into the stirring system. According to the findings, with high inertia (𝑅𝑒=100 ), the heat transfer inside the stirred tank is enhanced. Furthermore, increasing the nanoparticle fraction volume had a significant impact on the acceleration of heat transfer along the stirred vessel. It has been also found that the geometric configuration of an anchor with added arm blade (Case 2) is more efficient compared with the rest of the anchor agitator.

The present study proposes aerodynamically optimized exterior designs of a sport utility vehicle using computational fluid dynamics analysis based on steady-state Reynolds-averaged Navier–Stokes turbulence models. To achieve an optimal design, modifications of the outer shape and adding some aerodynamic devices are investigated. This study focuses on modifying this vehicle model’s upper and front parts. At the same time, the rear diffuser and spare tire on the back door as a fairing are used as aerodynamic devices for improving streamlines. All these modifications and add-on devices are simulated individually or in combination to achieve the best exterior design. A variety of Reynolds numbers are used for determining the optimization variables. Tetrahedral cells are used throughout the global domain because of the sharp edges in the geometry of the Discovery car model. At the same time, prism cells around car surfaces are adopted to improve the accuracy of the results. A good agreement between the numerical drag coefficient in the present study for the baseline models and the experimental data has been achieved. Changes in the drag and lift coefficients are calculated for all models. It is clear from the numerical results that the use of combined modifications and add-on devices has a significant effect in improving the overall aerodynamic behavior. As a result, the drag coefficient for the optimal design of the Discovery 4th generation is reduced from 0.4 to 0.352 by about 12% compared to the benchmark. Simultaneously, the lift coefficient is 0.037 for optimal design, and it is an acceptable value. It is found that combining all optimal modified configurations can improve both CD and CL simultaneously.

The current study investigates different methods to minimize the drag coefficient (CD) without ignoring the safety factor related to the stability of a vehicle, i.e., the lift coefficient (CL). The study was carried out by employing an SUV car analyzed numerically using one of the CFD software, Ansys. Four different models such as realizable k–ε, standard k–ω, shear stress transport k–ω, and Reynolds stress model (RSM). The considered models have been validated with experimental data and found in good agreement. The considered inlet velocity varies from 28 to 40 m/s, the results showed that the drag coefficient and the stability are both improved by applying a modification on the roof of the considered car.

Diesel engine characteristics were investigated experimentally while adding different concentrations of third generation biodiesel spirulina algae methyl ester (SAME). Three volumetric blends of SAME are added to standard Iraqi diesel, namely 10% SAME, 20% SAME, and 30% SAME. The properties of the fuels were found according to the American Society for Testing and Materials standards (ASTM). Experimental work was conducted on a single-cylinder diesel engine under variable load and compression ratio. Three compression ratios are used, starting from 14.5, 15.5, and 16.5. Based on the results obtained, the presence of SAME along with diesel caused an increase in Brake specific fuel consumption (BSFC), carbon dioxide (CO2), and nitrogen oxides (NOx) while decreasing both brake thermal efficiency (BTE) and exhaust gas temperature (EGT). Hydrocarbon (HC) emissions decreased by 7.14%, 8.57%, and 10.71%, for 10% SAME, 20% SAME, and 30% SAME, respectively, compared to the original neat diesel fuel. The dramatic carbon monoxide (CO) emission reduction was at full load point. The addition of SAME from (10 to 30)% reported a decrease in CO by (6.67–20)%. NOx, as well as CO2 emission, are increased as a result of SAME addition. The compression ratio change from (14.5/1 to 16.5/1) led to increased BTE, NOx, and decreased BSFC and all carbon emissions. The experimental results are validated with other studies' findings, and minor divergence is reported.

A numerical analysis of natural convective heat transfer in a square porous cavity with a solid wavy finite wall filled with (35% MWCNT-65% Fe3O4)/water hybrid nanofluid. The left wavy wall is heated to a constant temperature, the right wall is held at a low temperature, and the top and bottom walls are thermally insulated. Darcy-Brinkman-Forchheimer model is used to model porous medium with hybrid nanofluid. COMSOL Multiphasic Modeling Software via Galerkin finite element method has been used to solve the governing equations. The dimensionless parameters used in this investigation are; modified Rayleigh number (Ra* = 102, 103, 104, and 106), Darcy number (Da = 10–2, 10–4 and 10–6), Solid volume fraction (ϕ = 0.01, 0.03, and 0.05),undulation number (N = 1, 3, 5, and 7), amplitude of the wavy wall (A = 0.1, 0.2, and 0.3), and Prandtl number = 7.2 at constant high porosity. At a high Darcy number (Da = 10–2), the isotherm lines parallel to the vertical cavity walls, which means that conduction is the primary method of heat transport. At the same time, the convection mode is increasingly necessary at a lower Darcy number. The convection flow and the maximum amounts of stream function are reduced when both A = 0.1 and N = 1 increase. The average Nusselt number increases with increasing Ra*, while it decreases with increasing Darcy number and amplitude wave numbers. It has been determined that the largest improvement in heat transfer is at Ra* = 104, Da = 10–6, ϕ = 0.05, A = 0.1, and N = 1.

In process engineering as chemical and biotechnological industry, agitated vessels are commonly used for various applications; mechanical agitation and mixing are performed to enhance heat transfer and improve specific Physico-chemical characteristics inside a heated tank. The research subject of this work is a numerical investigation of the thermo-hydrodynamic behavior of viscoplastic fluid (Casson–Papanastasiou model) in a stirred tank, with introducing a new anchor impeller design by conducting some modifications to the standard anchor impeller shape. Four geometry cases have been presented for achieving the mixing process inside the stirred vessel, CAI; classical anchor impeller, AI1; anchor impeller with added horizontal arm blade, AI2 and AI3 anchor impeller with two and three added arm blades, respectively. The investigation is focused on the effect of inertia and plasticity on the thermo-hydrodynamic behavior (flow pattern, power consumption, and heat transfer) by varying the Reynolds number (Re = 1, 10, 100, 200), Bingham number (Bn = 1, 10, 50), in addition to the effect of geometry design in the overall stirred system parameters. The findings revealed an excellent enhancement of flow pattern and heat transfer in the stirred system relatively to the increase of inertia values. Also, an energy reduction has been remarked and the effect of anchor impeller shape. AI3 geometry design significantly improves the flow pattern and enhances heat transfer by an increased rate of 10.46% over the other cases.

In this paper, natural convective heat transfer in a rectangular cavity filled with (50% CuO-50% Al2O3)/water hybrid nanofluids connected to a wall containing a phase change material (PCM) has been experimentally investigated. The vertical walls were heated at varying temperatures while the horizontal walls were kept adiabatic. The considered parameters were the concentration of hybrid nanomaterial (Φ = 0.03, 0.05), the cavity inclination angle (θ = 0°, 30°, 45°), and the temperature difference between the hot and cold sides (∆T = 10, 15, 20 °C). The results have been validated and agree well with previously published papers. Furthermore, the main results stated that when the nanomaterial concentration increased, the heat transfer rate by free convection also increased. By increasing the natural convection flows via high temperature, symmetrical vortexes may appear near the heated wall. It also found that the PCM can potentially reduce the temperature of the hot side by up to 22% due to its high absorbability and heat storage. Furthermore, the inclusion of hybrid nanofluids in addition to the PCM enhanced its efficiency in heat storage and, therefore, its capacity to cool the hot side. Moreover, the influence of the inclination cavity enhanced the heat transfer, where θ = 30° was the optimal angle in terms of thermal conductivity.

The impact of green microalgae biodiesel, a biodiesel obtained from the ladophora and fucus species, on an alternative fuel process for diesel engines is investigated in this study. The research focuses on important components of a single-cylinder diesel engine’s combustion performance and emissions characteristics. Three distinct fuels were investigated for the experimental and numerical development: commercial diesel, a green microalgae biodiesel made from Cladophora and Fucus species material, and commercial diesel. The engine ran in three separate modes, all of which were tested according to international standards. The use of Cladophora and Fucus green biodiesel reduces thermal efficiency, according to the findings. Fuel usage is expected to rise by 6%. In comparison to diesel, the emissions analysis revealed that Cladophora and Fucus green biodiesel with less than 60%. Cladophora and Fucus in the biodiesel enables the minimization of pollutant levels of NOx and summary of emissions. When compared to diesel fuelled engines, the spray penetration and sauter diameter of the Fucus green diesel fuelled engine increased by 2.23% and 0.88%, respectively. NOx emissions and a summary of emissions, which are influenced by the inclusion of Cladophora and Fucus green diesel mixed fuel.

Experimental study of solar heat transfer in a Parabolic Trough Solar Collector (PTSC) recording to the Iraq weather conditions in Ad Diwaniyah city (32°N, 45°E). Different parameters used included varying the flow rate, focal length to test their effects on the performance of the collector. Three rates of water flow were used (2, 2.5 and 3 L/min). Results showed that; the performance of the collector increases when the mass flow rate increases. Furthermore, when the flow rate increased from 2-3 L/min, the useful heat gain and efficiency of the collector increased by 29 and 28%, respectively. It also, can be seen the performance of the collector decreases as the focal length increase. Two different methods have been used to increase the energy obtained from the solar collector. The first method by using of secondary reflectors and the second method by using of fins. Two configurations of secondary reflectors were used named as flat reflector and curved reflector. By using the first method, the efficiency of the collector increasing from 34.7-40.8% while it increasing from 35.5-38.44% when the second method used.

The behavior of convective heat transfer in an enclosure filled with Cu–water nanofluid with a baffle has been numerically studied using the finite element method. The enclosure’s top and bottom walls were adiabatic, while the other two were maintained at various temperatures. The left hot wall had an effective thickness and a baffle was added to the bottom wall. The influence of different parameters like the nanoparticle’s concentration (ϕ), Rayleigh number (Ra), the thermal conductivity ratio of the thick wall (Kr), baffle angle (Ø ), and the hot wall thickness (D) on the isotherm and fluid flow patterns were examined. The result showed that the average Nusselt number was enhanced, owing to the strength of the buoyancy force becoming more effective. Furthermore, as the baffle inclination angle increased, the maximum stream function at the core corresponded to the angle when it reached Ø=60∘ , then it gradually decreased to the minimum value as the baffle angle reached close to Ø=120∘ .

Natural convection and melting of ice as a phase change material dispersed with copper nanoparticles are numerically investigated. Square cavity filled with nano-mixture (Cu−ice) subjected to sinusoidal temperature distributions from the hot bottom boundary. The phase change process and heat transfer are formulated and solved using the enthalpy-based lattice Boltzmann method. Home-built numerical code is developed and validated. The effect of Rayleigh number (Ra = 104, 105, and 106) and copper nanoparticle concentration (ϕ = 0%, 1%, 3%, and 5%) on the flow characteristics and thermal performance of NePCM during the melting process is examined. According to the numerical results, the melting and charging times decrease by increasing the Rayleigh number. It is also observed that increasing the volume fraction of nanoparticle decrease melting time by up to 10%.

The double-diffusive mixed convection of MWCNT/water in a curvilinear cavity with split lid-driven and hot ellipses has been numerically studied in this paper. The top wall is split to move in different directions. The inclined walls, as well as the top wall, are cold with low concentration. Furthermore, the inner ellipses represent the heat source and high concentration, while the vertical and bottom walls are adiabatic. The considered variables are a range of Reynolds (50 ≤ Re ≤ 200), Richardson (0.1 ≤ Ri ≤10), Hartmann (0 ≤ Ha ≤ 30), Lewis (0.1 ≤ Le ≤ 10), bouncy ratio (−6 ≤ N ≤ 6), volume fraction (0 ≤ ϕ ≤ 0.08) and the direction of the split lid-driven at constant Prandtl (Pr = 6.2). The analysis has been done using the finite element method. The main results stated that the heat and mass transfers are greatly enhanced with the increase of Re number in the case of low Ri number, where Ri = 0.1 and Re = 50, the values of Nuavg and Shavg are equal to 7.4 and 10.7 and become 10.7 and 16.2 at Ri = 0.1, Re = 200 respectively. However, the effect of the Re becomes unnoticeable with a high Ri. Furthermore, Le has a positive effect on heat and mass transfer, and this effect increases with increasing Ri. For example, at Ri = 10 and Le = 1, Nuavg is 2.1 and Shavg is 2.2, whereas at Ri = 10 and Le = 10, Nuavg is 3.1 and Shavg is 4.6.

The proposed mathematical analysis intends to investigate the behavior of gyrotactic microorganisms to depict their significance in heat and mass transfer in unsteady magnetohydrodynamics (MHD) radiative Eyring–Powell nanofluid passing through a static/moving wedge. The Roseland nonlinear approximation was devised to incorporate solar radiation features into the energy equation, while the concept of gyrotactic microorganisms is used to govern the random movement of suspended nanoparticles. Additionally, the most recently revised model for nanofluid is used, which combines Brownian motion and thermophoresis effects. Through a convenient similarity method, the highly nonlinear partial differential equations (PDEs) with the auxiliary conditions have been translated into ordinary differential equations (ODEs) The altered equations are then utilized numerically via the spectral linearization method. Tables and graphs are used to demonstrate the influence of physical parameters on velocity, temperature, concentration, and motile microorganisms’ density profiles as well as the friction factor and Nusselt number, Sherwood number, and the motile density organism. It is noticed that fluid parameters decrease the velocity profile also enhanced the static and moving wedge. Moreover, a larger value of bioconvection Lewis number and Peclet number deprecates the motile density profiles. A comparison of current outcomes has been obtained with previous literature and is seen to be highly satisfactory.

In renewable energy systems, energy storage with phase change materials (PCM) is important, but these materials have poor thermal conductivity; therefore, approaches for improving the performance of these storage systems have become required. This research investigates numerically whether fins affect thermal energy storage (TES) units' behavior during phase changes. Three conductive fins at different positions were attached to the heated bottom wall to enhance the PCM melting process. Different dimensionless fin lengths (a/H = 0.25, 0.50, and 0.75) and dimensionless fin positions (b/L = 0.15, 0.25, 0.35, and 0.75) were considered as parameters to investigate their effect on melting rate. The main objective is to detect the best lengths of the fins and the optimum distance between them to achieve the highest storage performance. The enthalpy-based lattice Boltzmann technique is used to solve velocity and temperature fields for simulations. The results from other researchers validate the numerical predictions. It is found that significant enhancement in the heat transfer is shared between thermal conduction and convection at the initial and final stages of melting, respectively. Increasing the ratios fin lengths of a/H from 0.25 to 0.75, the whole melting period is shortened by 15.1%, 40.7%, and 70.1%, respectively. The best compromise positions ratio for short fins at a/H = 0.25 is b/L = 0.48 till the complete melting of PCM, while its b/L = 0.35 when the fine longer than a/H > 0.50.

Convective heat transport gives the remarkable behaviour in the many industrial procedure owing it mechanical behaviours of the system. A study has been obtained to analyse thermal radiative flow on unsteady MHD tangent hyperbolic nanoliquid near a stagnation point under viscous dissipation and chemical reaction. Also, thermal-diffusion and thermo-diffusion have been considered. The nonlinear PDE’s are altered into a set of ODE’s through suitable transformation and which are then numerically utilized. Further, numerical outputs for friction factor, Nusselt number and Sherwood are produced in table. Moreover, velocity distribution is increasing for a larger value of We and reduces for n. Moreover, similar behaviour is noted for temperature profile. A comparison with accessible outcomes for limited case is obtained with tremendous achievement.

Numerical study of natural convection around a heated trapezoidal block of different sizes located centrically in a larger trapezium has been investigated. The annulus between the trapeziums is filled with porous media. The sides of the inner trapezium are heated to a fixed temperature (T_h), and the slanted walls of the outer trapezium are adiabatic while its upper and lower walls are heated to temperatures of 〖T_c+(T_h-T_c)sin〗⁡(πx⁄L) and 〖T_h+(T_h-T_c)sin〗⁡(πx⁄L) respectively. The finite element numerical approach was used to solve the relevant dimensionless equations. Results are gotten for salient parameters including; modified Rayleigh number (10≤Ra_m≤ 1000), Darcy number (10^(-5)≤Da≤ 10^(-2)), and area ratio (1/5≤AR≤ 1/3). The results of this study are shown as isothermal contours, stream functions, and average Nusselt number. The results show that increasing Ra_m improves heat transfer; however, the response of thermal characteristics to AR increment depends on the range of Darcy number considered. Results from this study find application in ingot treatments and microchannel cooling among others.

The proper process of applying heat to many technological devices is a significant challenge. There are many nanofluids of different sizes used inside the system. The current study combines this potential to improve convection effects, considering numerical simulations of natural convection using Cu/water nanofluids in a square enclosure with bottom blocks embedded in baffles. The enclosure consists of two vertical walls with isothermal boundary conditions; the left wall is the sinusoidal heat source, whereas the right wall is cooled. The investigations dealt with the influences of nanoparticle concentration, Rayleigh number, baffle length, and thermal conductivity ratioon isotherms, stream functions, and average Nusselt number. The results present that, when the Rayleigh number rises, the fluid flow velocity increases, and the heat transfer improves. Furthermore, the baffle length case (Lb = 0.3) provides higher heat transfer characteristics than other baffle height cases.

The current study aims at studying the viscous dissipation and chemical reaction of higher-order Casson nanofluid flow and entropy exploration along with MHD and electric field influences. The PDE guiding the model is transformed into nonlinear ODE by applying adequate similarity transformations. Further, the equations are worked out using the Keller Box method. The influence of several parameters is observed by constructing velocity, temperature, and concentration graphs using MATLAB. It is observed that entropy shows a rising tendency in the case of radiation parameter, Eckert number, decays for Casson parameter, temperature raises for radiation, Eckert parameters, and decays for Casson parameter. Velocity profiles decay for the Casson parameter. Also, local parameters skin friction, Nusselt number, and Sherwood numbers are calculated for Casson parameter, which is a function of Hartmann, number, Brownian motion parameter, thermophoresis parameter, which is a function of electric field parameter.

The current article presents a numerical simulation of the nanofluid convection inside a square enclosure with two inner adiabatic circular bodies. Galerkin finite-element analysis was utilized to solve the governing equations under the assumptions of laminar, steady flow conditions considering a homogeneous single-phase approach. The parameters under investigation are Rayleigh number (Ra), solid volume fraction, the horizontal position of the two inner cylinders, and the inclination angle of the enclosure. The results indicate that increasing the Rayleigh number, and the solid volume fraction improves the heat transport rate. It is obtained that at low Ra, there is no significant impact on the enclosure angle, while as the Ra goes up, the heat transfer rate increases gradually. In addition, the best location of the internal bodies is in the middle of the cavity as it exhibits an increase in the flow velocity. To obtain the highest Nusselt number, it is recommended to use an inclination angle of 30 at any value of the Rayleigh number.

A numerical study was conducted to determine the impact of MHD on mixed convection of a Cu-water nanofluid in a horizontal channel attached to two open enclosures filled with a porous material is implemented in this paper. Uniform heat is supplied on the base of the two enclosures while the other walls are considered adiabatic. The finite element method has been utilized in this study to solve the considered equations and other numerical simulations that needed to be validated, assessed with previous papers to ensure that the model works correctly. Furthermore, this study considers a range of each of the Reynolds number (Re 25, 50, 100, 150, 200), Richardson number (Ri 0.1, 1, 3, 5, 8, 10) and the Hartmann number (Ha 0, 5, 10, 15, 30, 50) at a constant volume fraction ( 0.08) and porous media properties (Da 10-2, and 0.7). The results stated that the strength of the streamlines, isotherms, and the average Nusselt number (Nu increases with increasing values of the Richardson and Reynolds numbers while they decrease upon increasing the Hartmann number. The result shows that no big difference between cases 2 and 3, and the maximum enhancement in Nu is 9.84% in case 2 compared with case 1 at Re = 200, Ri = 1, and Ha = 0.

This study investigates the implications of the area ratio (AR) and Grashof number (Gr) on fluid flow properties and heat transfer due to mixed convection around heated trapezoidal blocks located concentrically inside a larger trapezium driven by a lid. The outer trapezium's upper and lower horizontal walls are moving in opposite directions. The model developed was solved using the finite element technique. The inner walls of the trapezium are retained at an isothermal temperature, while the slanted outer walls of the trapezium are perfectly insulated. The upper and lower walls of the enclosure are subjected to normalized sinusoidal temperatures. Grashof number in the range of 103£Gr£105 and area ratios ( ) of , and were investigated. The simulation outcomes are displayed as stream function, isothermal contours, and local Nusselt number. Considering the interval of for the inner block, the Nusselt number increase with diminishing area ratio for the upper wall, while the response of the lower wall to Gr variation is a function of the AR considered. At the bottom wall of the outer trapezium, results showed that the rate of heat transfer was not significantly affected by changes in area ratio. Furthermore, as the AR reduces, the heat transmission along the top wall of the outer trapezium improves with the Grashof number, with the least and peak heat transfer enhancements occurring at 50 % and 100 % percent of the wall length, respectively.

The influence of the helical grooved path in the pipe was studied in the fully developed region of the pipe in this study. In fact, the applicable depth and pitch ratios minimize the cost and the production time of the manufacturing process. The Finite Volume Method (FNM) has been used with RNG k-ε turbulent model in this study. Heat and fluid flow in a pipe with a diameter of 0.25 m and a length of 5 m have been simulated. The improvement area starts after 3 meters, which represents to fully developed region, as examined and confirmed. The results showed that the efficiency improved by 5.8% compared to the plain pipe.

The impacts of MHD and heat generation/absorption on lid-driven convective fluid flow occasioned by a lid-driven square enclosure housing an elliptic cylinder have been investigated numerically. The elliptic cylinder and the horizontal enclosure boundaries were insulated and the left vertical lid-driven wall was experienced at a fixed hot temperature, and the right wall was exposed to a fixed cold temperature. COMSOL Multiphysics 5.6 software was used to resolve the nondimensional equations governing flow physics. A set of parameters, such as Hartmann number ( ), Reynolds number ( ), Grashof number ( ), heat generation-absorption parameter ( ), and elliptical cylinder aspect ratio (AR) ( ) have been investigated. The current study discovered that for low Reynolds number, the adiabatic cylinder AR of 2.0 provided the optimum heat transfer enhancement for the model investigated, also the impact of cylinder size diminishes beyond Gr = 104. But for high Reynolds (Re = 1000), the size of the cylinder with AR = 3.0 offered the highest heat transfer augmentation. The clockwise flow circulation reduces because of an increase in AR, which hinders the flow circulation. In addition, heat absorption supports heat transfer augmentation while heat generation can suppress heat transfer improvement.

A study is conducted to determine the impact of joule heating, thermo-diffusion, and chemical reaction effect on wedge flow with melting. Using similarity transformation, the nonlinear PDEs regulate nanofluid flow is converted to nonlinear ODEs. The MATLAB solver is used to solve the boundary value problem numerically. The interaction of relevant physical entities on nanoparticle concentration, nanofluid temperature, nanofluid velocity, skin friction, rate of heat, and mass transfer is graphically portrayed. This study will aid in the development of cooling devices and various shapes in heat sinks, as well as improving the heat transfer characteristics of Casson flow and strengthening formerly industrial uses. In the limiting situation, current findings are compared to analysis of findings. Flow velocity and concentration compacts in association with enhancing values of chemical reaction factor while temperature increases with enhancing the values of chemical reaction parameter. An upsurge in the temperature of the fluid is seen with the increasing Eckert number. It is found that the melting process increases the thicknesses of Solutal, thermal, and momentum boundary layers while it reduces mass transfer rate, heat transfer rate, and Skin friction. The Casson fluid displays a superior heat transfer mechanism than the Newtonian fluid. This study would be valuable in designing cooling gadgets and heat sinks of various shapes which will enhance the heat transfer properties of Casson nanofluids thereby increasing their applications in industrial perspectives. Moreover, the study reveals the novel applications of Casson nanofluids in cooling devices and heat sinks.

In the current work, numerical simulations are achieved to study the properties and the characteristics of fluid flow and heat transfer of (Cu–water) nanofluid under the magnetohydrodynamic effects in a horizontal rectangular canal with an open trapezoidal enclosure and an elliptical obstacle. The cavity lower wall is grooved and represents the heat source while the obstacle represents a stationary cold wall. On the other hand, the rest of the walls are considered adiabatic. The governing equations for this investigation are formulated, nondimensionalized, and then solved by Galerkin finite element approach. The numerical findings were examined across a wide range of Richardson number (0.1 ≤ Ri ≤ 10), Reynolds number (1 ≤ Re ≤ 125), Hartmann number (0 ≤ Ha ≤ 100), and volume fraction of nanofluid (0 ≤ φ ≤ 0.05). The current study's findings demonstrate that the flow strength increases inversely as the Reynolds number rises, which pushes the isotherms down to the lower part of the trapezoidal cavity. The Nuavg rises as the Ri rise, the maximum Nuavg = 10.345 at Ri = 10, Re = 50, ϕ = 0.05, and Ha = 0; however, it reduces with increasing Hartmann number. Also, it increase by increasing ϕ, at Ri = 10, the Nuavg increased by 8.44% when the volume fraction of nanofluid increased from (ϕ = 0–0.05).

The present work examines numerically the heat transfer and the buoyancy-driven flow within a U–shaped baffled enclosure filled with a nanofluid-saturated porous medium in the presence of an inclined magnetic field using a finite element scheme. The enclosure bottom wall is heated sinusoidally while the two baffles and the inner walls are maintained at a constant cold temperature. The rest walls of the enclosure are kept adiabatic. The parameters under investigation are Hartmann number (Ha), volume fraction (φ), Darcy number (Da), Rayleigh number (Ra), nanoparticles aspect ratio (AR), and the angle of applied magnetic field (γ). The results are crucial and illustrate that increasing the values of Ra, Da and the nanoparticles volume fraction enhances the heat transfer while the Hartmann number inversely affects the heat transfer augmentation. Moreover, the average Nusselt number (Nuave) increases by increasing the enclosure aspect ratio. For the geometry under consideration and for a better heat transfer rate, it is recommended to choose an AR = 0.6 at Ha = 0 with a 0.1 vol fraction.

Numerical analysis of fluid flow and natural convection heat transfer of Fe3O4-water nanofluid around a heated rectangular cylindrical barrier placed in a square cavity was conducted using COMSOL Multiphysics 5.5 software. The effects of nanoparticles volume fraction (0≤ϕ≤0.06), aspect ratio (0.1≤AR≤0.7), and Rayleigh number (10^2≤Ra≤10^6 ) on heat transfer and fluid flow due to natural convection in the cavity were analyzed. The heated rectangular cylinder walls were set to have a higher constant temperature while the enclosure walls were maintained at a lower fixed temperature. Results are reported in form of velocity streamlines, isothermal contours, local and average Nusselt numbers. Also, the average Nusselt number for all the walls of the heated rectangular cylinder was found to be independent of Rayleigh number in the range of 10^2≤Ra≤10^3 for the various nanoparticle volume fractions (0≤ϕ≤0.06) considered. Furthermore, the average Nusselt number of the walls of the cylinder increases with increasing Rayleigh number and aspect ratio.

In this paper, the thermal behavior of concrete blocks with different rubber ratios was examined experimentally. The rubber of 0%, 5%, 10%, 15%, and 20% used instead of fine aggregate in a concrete block raw materials. The size of the rubber granules used in this study is between 0-1 mm. The concrete approved mixing ratios are 1:2:1. The indoor solar simulator with 700 w/m ² light intensity was applied on the external surface of each block and thermocouples were used to measure the temperature on the external and internal surfaces. The other block surfaces are insulated. The results indicated that the use of rubber aggregate with the concrete block reduced the inner surface temperature by increasing the thermal resistance of the heat flux. For 20% rubber added, produce 8.5% low-weighted construction materials and with high thermal resistance that works to save energy consumed in the building sector.

The current study summarizes previous studies carried out on heat convection, fluid flow, and entropy generation of porous enclosures filled with hybrid/nanofluid. Newtonian and non-Newtonian base fluids and the magnetohydrodynamics effects are considered. Natural convective heat transmission is one of the most common types of heat transfer due to its wide engineering applications like solar collectors, electronic equipment, cooling systems, nuclear reactors, and geothermal engineering. By offering a large surface area per unit volume and the disorderly movement of fluids passing through the relevant pores, in several applications, a porous media can increase convective heat transmission. Moreover, the problem related to the low thermal conductivity of conventional fluids can be addressed by introducing nanoparticles known as nanofluids. To increase the performance of thermal equipment, combining nanofluids with porous materials can be very advantageous. The impact of different governing parameters and the numerical methods used to solve the differential equations are also summarized.

The current article aims to discuss the natural convection heat transfer of Ag/Al2O3-water hybrid filled in an enclosure subjected to a uniform magnetic field and provided with a rotating cylinder and an inner undulated porous layer. The various thermo-physical parameters are investigated such as Rayleigh number ( ), Hartmann number ( ), and the nanoparticles concentration ( ). Likewise, the rotational speed of the cylinder ( ), as well as several characteristics related to the porous layer, are examined li its porosity ( ), Darcy number ( ) which indicates the porous medium permeability and the number of undulations ( ). The calculations are carried out based on the Galerkin Finite element method (GFEM) to present the streamlines, isotherms, entropy generation, and average Nusselt numbers in details. The main results proved that increment of Rayleigh number and Darcy number enhances heat transfer convection within the enclosure. Whilst, the porosity presents a minimal impact. Also, the rotational speed in a positive direction has a favorable influence on the heat transfer dispersion across the cavity.

The main resource of this paper is to establish over fluid flows sheet using mathematical modeling for constant and variable thickness by including magnetic fields, electric fields, porous medium, heat propagation/immersion, and radiative heat relocation. The Implicit Finite Difference Method (IFDM) is applied to simplify using similarity conversions to implicate partial differential equations to convert into ordinary differential equations. IFDM has been implemented in MATLAB to tabulate numerical observations of the local parameters. Nusselt and Sherwood numbers are analyzed and measured for different parameters in different constant and variable thickness conditions of fluid properties. The influence of various parameters is explained through temperature, velocity, concentration, and nanoparticle volume fraction graphical representations. The coefficient of the skin friction for irregular fluid properties is shown to have a greater influence than that compared for constant fluid properties. Nevertheless, there is a reverse case in the local Nusselt number that is lower for the fluctuating fluid properties than with constant fluid properties. The results showed high-exactness computational outcomes are attained from the IFDM.

The present work aims to investigate numerically the effect of LPG blending on the characteristics of diesel engines subjected to variable compression ratio, injection timing, and engine speed. Three blends of LPG are used, which are 10% LPG + 90% diesel, 20% LPG + 80% diesel, and 30% LPG + 70% diesel. The numerical investigation is carried out using the simulation software Diesel-RK. Increasing the percentage of LPG in diesel starts combustion early where the lowest delay period is recorded for a blend of 30% LPG + 70% diesel 6.36 deg. The combustion pressure and heat release are decreased due to the difference in the heating values of blended fuels. Although the peak energy release for diesel is 0.05458 (1/deg.) at 375 deg. BTDC, it was 0.0542, 0.05424, and 0.0537 (1/deg.) at 375 deg. BTDC for 10%, 20%, 30% LPG, respectively. Diesel with 30% LPG has a higher spray penetration followed by 20% LPG then 10% LPG and diesel come last. The diesel with 10% LPG gives a 5.35% reduction in NOx, while diesel with 20% and 30% LPG emit less NOx emission by 9.05% and 16.5%, respectively. Increasing the percentage of LPG in diesel yields to reduce soot concentration because LPG has lower carbon to hydrogen ratio. The lowest ability to emit smoke is detected for fuel with 30% LPG where a 7.4% reduction is obtained. It is worth noting that blending LPG with diesel can fight the trade-off relation between Soot-NOx as a reduction in both of them is obtained. Based on the results obtained, the blending ratio is 30% LPG. The obtained results are validated with the results of other researchers.

This numerical study is intended for the analysis of thermal convection induced by buoyancy forces generated within a conical annular porous gap. The annulus was vertically positioned, it contains a discrete heat source and is filled with a Single-Walled Carbon Nanotubes-Water (SWCNT- O) nanoliquid exposed to a Lorentz force. To describe the porous medium in question, we have adopted the Darcy–Forchheimer model. Galerkin Finite Element Method (GFEM) has been used in this study to predict both thermal and hydrodynamic fields in the physical model. An extensive range of parameters are explored, i.e., the Rayleigh number (103 to 106), Hartman number Ha (1 to 100), and the volume fraction of nanoparticles (0 0.08). For the purpose of exterminating the effects of heat source location on thermal and hydrodynamic fields, three locations (bottom, middle and upper) have been considered. Findings include current lines, isotherms, and Nusselt number evolution according to the previously stated variables. Predictably, our findings prove that heat transfer rate exhibits a decreasing function of Ha and an increasing function of Da and . Also, it was revealed that the convective regime is preponderant when the heat source was located in the bottom wall.

The gas turbine blade stator is subjected to a severe high temperature of hot incoming gases from the combustor. In order to avoid the melting of the stator, film and internal cooling techniques are applied by using a bypass stream of air from the compressor as a coolant fluid. These techniques have their own merits, but it is limited by some constraints like the value of specific heat of air. In this paper different gases with higher specific heat are used as a coolant in order to increase the thermal capacity of coolant fluid which in turn increases the amount of transferred heat. The selected gases are Helium, Steam, and Ammonia are applied in COMSOL Multiphysics® in order to simulate the cooling process and the temperature distribution. At first, the air is applied and the results show a good agreement with previous literature and then the other coolants to compare their results with the air. The results show that the Helium affects the cooling process strongly and it cools the blade to safer limits rather than air by about 50%, but it increases von Mises stress by about 71% in comparison with air. The two other coolants also have a good and effective cooling performance, but they almost show an identical performance.

Great attention is directed towards the study of the spray phenomena theoretically and experimentally due to its dramatic effect on the combustion process that occurred in an internal combustion engine, in particular, the diesel engine. The spray macroscopic characteristic of diesel engines fueled with two different biodiesel fuels in addition to nominal diesel under various injection pressures has been investigated numerically in this work. The selected biofuels are Rapeseed methyl ester (RME), Waste cooking oil methyl ester (WCOME). The Russian simulation software Diesel-RK is used in this work. Four different injection pressures are used which are 200, 500, 800 and 1000 bar respectively. It is found that RME has higher spray penetration with a narrow spray angle due to high viscosity and large momentum compared to diesel fuel. The results reported that biodiesels have greater Sauter mean diameter (SMD) compared to pure diesel because of their higher viscosity and surface tension. Promising reduction in SMD comes with WCOME as the injection pressure increases. Cylinder pressure along with heat release is reduced in the case of biodiesel due to the reduction in heating values. The lowest ability to produce smoke is recorded for WCOME where 93% reduction is achieved followed by a 57% reduction for RME as compared to diesel. The obtained results are compared with the results of other researcher and the convergence between them is observed.

Numerical simulation of MHD free convection in a two-dimensional trapezoidal cavity of a hybrid nanofluid has been carried out in this research. The cavity is heated sinusoidal from the bottom wall, and the inclined walls are cooled while the top wall is isolated. The hybrid nanofluid (MgO-Ag/water) has been used as a working fluid. The numerical simulation has been validated with past papers and met a good agreement. The considered parameters are a range of Rayleigh number (Ra= 103 to 106), Hartmann number (Ha= 0 to 60) and volume fraction (f= 0 to 0.02). The results are presented as isotherms, stream functions, local and average Nusselt numbers, from which it is observed that the strength of the stream functions and isotherms increases with the increase of the Ra and ϕ while the increase in Hartmann number reduce the circulation of the flow and increases the isotherms strength. Also, the Nusselt number is increases with Ra and ϕ while it decreases with Ha.

The main goal of this study is to investigate double-diffusive natural convection in a complex enclosure containing two equilateral triangular obstacles. The triangles and the horizontal walls are isolated, while the left and right vertical walls are considered at high and low temperatures and concentrations, respectively. The evolved transport equations are solved numerally using Galerkin finite element method. To depict the influence of pertinent physical parameters on the heat and mass transfer, the study explored a range of parameters like Rayleigh number (Ra = 104–106), Lewis number (Le = 1–10), the ratio of buoyancy (N = − 5–5), and size of the inner triangle (TL). The obtained results are presented through stream functions, isotherm, and iso-concentration contours. Moreover, the average Nusselt number (Nuavg) and the average Sherwood number (Shavg) are also computed to study the effect of considered factors on heat and mass transfer. The result indicates that, as Ra and N increase, both Nuavg and Shavg increase, whereas they decrease when the TL ratio increases. On the other hand, when Le increases, Nuavg decreases, and Shavg increases. Also, it finds that, when TL increases, the maximum reduction in Nuavg and Shavg is about 15.3% and 5.1% respectively, at N = 4, Le = 4, and Ra = 106.

The influence of applying an external distributed pressure along the upper surface of the molten metal (Aluminum ) during the solidification process on the temperature reduction profile was studied including the time of solidification of the cast and the phase change moving boundary location for two mould wall thicknesses (10mm and 15mm). A 3D model was built up by Solidworks and simulated by ANSYS FLUENT; each mould wall thickness was discussed for two press cases (1bar and 3bar) sequentially, comparing with no press cases. The discussion includes the ambient temperature effect, which is taken (300K then 310K), the overall cases that studied was 7 cases. The study shows a remarkable effect of press on the temperature reduction profile especially when mix with the mould thickness effect as well as the ambient temperature which has a great order in guiding the results. The results showed that the heat reduction increases by increasing the mould thickness as well as the applied pressure. Moreover, this effect will reduce the solidification time and the moving of the boundary of phase change become faster in appearance.

The mixed convective heat transfer has many multiple engineering applications, such as solar collectors, electronic equipment cooling and heat exchanger, and geothermal engineering. This work presents comprehensive coverage of a wide range of published studies in terms of convection heat transfer inside the enclosure in recent years. The convective heat transfer in porous media with/without nanofluid, and the effect of stationary/rotating cylinder inside cavities, as well as the position of the cylinder, had been addressed and discuss to draw the main conclusions and recommendations. It is worthy to mention that the mixed convective with the effect of entropy generation with inner bodies in enclosure has been investigated less than the other simple enclosure shapes due to its complexity. The researchers can be extended their future studies by adding the MHD effects with mixed conviction in simple/complex shapes of enclosure. This study gives an important and useful summary for provides researchers of heat transfer in academic and industrial. At the end of this investigation, the governing equations of the 2-D mixed convection in an enclosure filled with porous medium, and nanofluid addressed.

The present study investigates mixed convective and fluid flow characteristics in a lid-driven enclosure filled with air and its walls subjected to various heating conditions. The vertical (left and right) walls of the enclosure are cooled (Tc), and the bottom wall is heated to (Th) while the horizontal lid-driven upper wall is subjected to sinusoidal heating. The dimensionless governing equations (continuity, momentum, and energy transport) were implemented in COMSOL Multiphysics 5.4 software. The influences of Grashof number (103 ⩽ Gr ⩽ 105 ) and Reynold number in the interval of 1 ⩽ Re ⩽ 100 on the average Nusselt number ( NU ) for all walls of the cavity was examined. Furthermore, the results presented in the form of isotherms, streamlines, and the local and average Nusselt numbers in the enclosure for Re ⩽ 100 and Gr in the range of 103 ⩽ Gr ⩽ 105. The results indicated the highest and lowest average rate of heat transfer at the bottom and top walls of the cavity respectively. The top wall region presented a higher velocity as confirmed by the velocity contour plots.

In this paper, the performance characteristics of an ejector-expansion refrigeration cycle (EERC) using R410A are investigated in comparison with that using R22 based on first- and second-law perspectives. For this purpose, a numerical model of constant mixing pressure is developed and a parametric study of the effective design parameters is implemented. The results show that at evaporation temperature ( T e ) and condensing temperature ( T c ) equal to 5 ∘ C and 4 0 ∘ C, respectively, the coefficient of performance (COP), exergy efficiency and volumetric cooling capacity (VCC) of the R410A EERC is improved by 12.91%, 12.89%, and 10.8%, respectively. Compared with the conventional refrigeration cycle, the EERC is more beneficial at lower evaporation temperature and higher condensing temperature. The COP of R410A EERC, exergy efficiency and VCC improvements over the regular refrigeration cycle are also greater than that of R22 by about 34.7%, 32.3% and 31%, respectively. Exergy analysis shows that applying an ejector in lieu of a throttle valve improved the energetic efficiency by 7.793–15.42% and by 10.59–22.79% for R22 and R410A, respectively, for the given range of evaporating and condensing temperature. In addition, the effects of the suction nozzle pressure drop, area ratio and the component efficiencies of the ejector on the EERC performance are analyzed.

In this paper, double-diffusion natural convection for staggered cavities with a concaved lower wall is investigated. The finite volume procedure is utilized to solve the governing equations along with the boundary conditions. The current code is validated with previously published results. Impacts of Rayleigh number (104 ≤ Ra ≤ 106), buoyancy ratio (− 5 ≤ N ≤ 5), Lewis number (1 ≤ Le ≤ 5), and aspect ratio (0.1 ≤ AR ≤ 0.2) on the flow characteristics are investigated and presented as isotherms, streamlines, and iso-concentrations contours. Moreover, alterations of average Nusselt and average Sherwood numbers with these parameters are analyzed and discussed thoroughly. It is found that average Nusselt and average Sherwood numbers augment with Rayleigh number and buoyancy ratio for aiding flows. These also are found to decrease with decreasing buoyancy ratio for opposing flows. Also, it is elucidated that the aspect ratio has an inverse relationship with average Nusselt and average Sherwood numbers in which the depression in these numbers is determined to be 10.4%.

In this study, a numerical investigation of mixed convective heat transfer in a square enclosure partitioned in two layers with a rotating circular cylinder at the middle of the cavity has been carried out. The experiments are performed with Al2O3–water nanofluid (upper layer) and superposed porous medium (lower layer). The upper and lower horizontal walls are assumed to be insulated, while the left and right walls are kept at high and low temperature respectively. Galerkin finite element method has been used to solve the dimensionless governing equations. This study is focused to investigate the effect of Darcy number (10−2≤ Da ≤10−5), Rayleigh number (103≤ Ra≤106), dimensionless angular rotational velocity (−6000≤ W ≤ 6000), solid volume fraction (0≤ ɸ ≤0.06), and the radius of the inner circular cylinder (R = 0.1, 0.2 and 0.3) on the heat transfer, fluid flow, and the physical characteristics thermal of the thermal fields. The results show that the intensity of the flow, steep temperature gradient, and the average Nusselt number (Nu) increase with increasing the value of Darcy number, Rayleigh number, and solid volume fractions at any cylinder radius. Moreover, the recirculation and isotherm distribution lines of the fluid at low Darcy numbers are high when the cylinder rotates counter-clockwise compering with clockwise. The findings also revealed that when W = 0, the maximum Nu is at R = 0.1 and decreases as the cylinder radius increases. Moreover, at high Darcy number, the highest local Nusselt number is found at the porous layer region in case of clockwise rotation while at the nanofluid layer region in case of anti-clockwise rotation.

A comprehensive review on wide range of studies on natural convection was published relevant to enclosures especially for the nanofluid enclosures which were exposed to different conditions on its boundary wall. The papers related to the ways that used to enhancement the naturalconvection heat transfer of a nanofluid within an enclosure region had been discussed in full details. Also contains the experimental and numerical studies related to naturalconvection heat transfer of a nanofluid.It is of practical and scientific importance to several engineering applications, such as industrial cold-storage installations and insulation for buildings. There are researchers attracted their attention and interested in studying the thermophysical characteristics of the nanoparticle more than anything else of the studies and did not focus on the characteristics of heat transfer by this new fluid. There was a series of investigations and several experimental and numerical studies were investigating within a square shape cavity using nanofluids as working fluidand with the effect of the conductive baffle has a variable-length attached to the bottom horizontal wall.It was found that there is a lot of things need to be investigated for studying the nanoparticle size and shape influence on the natural convection heat transfer inside an enclosure

Numerical investigate of double-diffusive natural convection in an inclined porous square. Two opposing walls of the square cavity are adiabatic; while the other walls are, kept at constant concentrations and temperatures. The Darcy–Forchheimer–Brinkman model is used to solve the governing equations with the Boussinesq approximation. A code written in FORTRAN language developed to solve the governing equations in dimensionless forms using a finite volume approach with a SIMPLER algorithm. The results presented in U-velocity and V-velocity, isotherms, iso-concentration, streamline, the average Nusselt number, and the average Sherwood number for different values of the dimensionless parameters. A wide range of these parameters have been used including; Darcy Number, modified Rayleigh number, Lewis number, buoyancy ratio, and inclination angle. The results show that for opposite buoyancy ratio (N≤-1), the Nu decreases when the Le increases and the Sh increase when the Le increases. For an (N>0), the Nu increases when the Le increases until Le is equal to 1 and then it decreases, also Sh increases when the Le increases

The effect of twisted tape ratio has been studied numerically to promoting a swirl effects inside a long half-length pipe. A constant wall temperature demonstrates solar collector at average temperature conditions for the receiver pipe. The flow simulation adjusted at different range of Reynolds number 1500-7000 and varied twisted tape ratio y=2, 3.3, and 5. The results showed that; when the twisted tape pipe increases (for example at 3.4), the average outlet temperature, heat transfer coefficient, Nusselt number, friction factor, and power losses increases to 64, 65, 28, 14.1, 31 % respectively compared with plain pipe, also the average outlet fluid temperature is maximum from 305 K-322 K at low Reynolds number 1500 for all cases and then will be decreasing with increasing Reynolds number .The results presented in contours of temperature distribution and flow trajectory by axial velocity were accomplished to exam the low Reynolds number in solar applications. It showed that, when the swirl geometry used, which would be effect on the axial velocity for the flow by 10 % more than the cases without twist tape.

The characteristics of the conjugate natural convection of (Al2O3-water) nanofluid inside differentially heated enclosure is numerically analyzed using COMSOL Multiphysics (5.3a). The enclosure consists of two vertical walls, the left wall has a thickness and maintain at a uniform hot temperature, while the opposite wall at cold temperature and the horizontal walls are isolated. A high thermal conductivity thin baffle has been added on the insulated bottom wall at a different inclination angles. The effect of the volume fractions of nanoparticles (f), Rayleigh number (Ra), solid wall thermal conductivity ratio (Kr), baffle incline angles (Ø) and the thickness of solid wall (D) on the isothermal lines, fluid flow patterns and the average Nusselt number (Nu) has been investigated. At low Rayleigh number (Ra=103 to 104) the Isothermal lines are parallel with the vertical wall which is characteristic of conduction heat transfer. on the other hand, when Rayleigh number increase to (Ra=106), the isotherms lines distribution in the inner fluid become parallel curves with the adiabatic horizontal walls of the enclosure and smooth in this case convection heat transfer becomes dominant. As the Rayleigh number further increases, the average Nusselt number enhance because of buoyancy force become stronger. In addition, the fluid flow within the space is affected by the presence of a fin attached to the lower wall that causes blockage and obstruction of flow near the hot wall, hence the recirculation cores become weak and effect on the buoyant force. The maximum value of the stream function can be noticed in case of nanofluid at (Ø=60), whereas they decrease when (Ø > 60), where the baffle obstruction causing decreases in flow movement. So that the left region temperature increases which cause reduction of the convective heat transfer by the inner fluid temperatures. This is an indication of enhancing of insulation. When the inclination angle increases (Ø >90), the baffle obstruction on flow and fluid resistance becomes smaller and the buoyancy strength increase, as a result, the heat transfer is increasing in this case. As a result of increasing the thermal conductivity from 1 to 10, an increase in the amount of heat transferred through the solid wall to the internal fluid have been noticed. This change can be seen in the isothermal lines, also, there was growth and an increase in the temperature gradient. The increasing of wall thickness from (D=0.1 to 0.4) leads to reduce the intensive heating through the solid wall as well as small heat transferred to the inner fluid. Therefore, it can be noticed that when the wall thickness increases the stream function decrease.

A numerical investigation is presented to illustrate the impact of aspect ratio in a conjugate heat transfer enclosure filled with porous media and partially heated from vertical walls. The left and right walls are partially heated and cooled, respectively. The remaining partitions of the vertical walls in addition to the top and bottom walls are considered to be adiabatic. the present work is limited to two different cases: Top-Bottom (case 1) and Bottom-Top (case 2). The dimensionless Navier-Stokes governing equations are solved using the finite element method. The parameters of interest are the modified Rayleigh number 10 ≤ Ra ≤ 103, the finite wall thickness 0.02 ≤ D ≤ 0.5, 0.1 ≤ Kr ≤ 10 and the aspect ratio 0.5 ≤ A ≤ 10. The results are presented in term of streamlines, isotherms and average Nusselt number for fluid phase and along the solid hot wall. The results indicated that the locations of partially active walls have great influence on heat transfer rate. I was shown that Bottom-Top arrangement gives better heat transfer rate compared to that of Top-Bottom. It was also found that by increasing the Rayleigh number, the rate of heat transfer increased. In contrast, increasing the wall thickness and aspect ratio reduced the heat transfer rate.

The conjugate natural convection heat transfer in a partially heated porous enclosure had been studied numerically. The governing dimensionless equations are solved using finite element method. Classical Darcy model have been used and the considering dimensionless parameters are modified Rayleigh number (10 ≤ Ra ≤ 103), finite wall thickness (0.02 ≤ D ≤ 0.5), thermal conductivity ratio (0.1 ≤ Kr ≤ 10), and the aspect ratio (0.5 ≤ A≤ 10). The results are presented in terms of streamlines, isotherms and local and average Nusselt number. The results indicate that heat transfer can be enhanced by increasing the modified Rayleigh number, and thermal conductivity ratio. Wall thickness effects on the heat transfer mechanism had been studied and it is found that; as the Wall thickness increases, the conduction heat transfer mechanism will be dominated. Also, increasing aspect ratio will increase the stream function and reduced the heat transfer rate

Natural convection heat transfer in a porous rectangular partially active heated wall is numerically investigated using finite element method. Three different cases of heating and cooling zone had been taken in the consideration along the vertical walls while the others are considered to be adiabatic. The governing equations are obtained by the applying of Darcy Model and Boussinesq approximation. Finite element method is used to solve the dimensionless governing equations with the specified boundary conditions. The investigated parameters in the present study are the modified Rayleigh number (10 •Ra • 103), aspect ratio (0.5 • A• 2), finite wall thickness (0.02 • D•= 0.5) and the thermal conductivity ratio (0.1• Kr • 10). The results are presented in terms of streamlines, isotherms and Nusselt number. The results indicate that as the aspect ratio, finite wall thickness increase, Nusselt number decrease. Also, as the modified Rayleigh number increases, the Nusselt number will increase. Case 1 and 2 gave approximately the same effects of heat transfer rate while case 3 give lower rate of heat transfer rate.

Thermal and hydrodynamics performance of1shell and 2-tubes heat exchanger with different concentrations of ethylene glycol, copper and alumina as nanofluid have been investigated, theoretically and numerically. The heat exchanger is 1shell-multiple pass with eight bend pipes. The hot water is flowed in the bend tubes and cooled by water with different types of nanoparticles in the shell flow. Three different types of nanoparticles, which are (ethylene glycol, copper and alumina), have been used in water as a working nanofluid. The results show that; the water-copper and water-alumina nanofluid have the best performance enhancement of the heat exchanger than ethylene glycol with effectiveness 0.175. Additionally, the minimum friction factor appears when the copper and alumina particles used. The numerical results are in a good agreement with theoretical results and the maximum percentage error of the effectiveness equal to 4%. NOMENCLATURE B Baffle spacing [m] b f Basic fluid C Heat capacity rate [kJ/(kg.K)] C p Heating capacity [kJ/(kg.K)] C r Ratio of heat capacity rate D Diameter [m] F Friction factor H Heat transfer coefficient [kW/(m2.K)] u m Mean velocity [m/s] K Thermal conductivity [kW/(m.K)] L t Tube length [m]

A water cooling system based on Peltier Effect has many benefits as being small in size, portable, noiseless, environmental friendly and economical compared to conventional cooling systems. This research focuses on the thermal performance experimental study of a portable thermoelectric water cooling system. During this study, the applied voltage on TE was changed to determine its effect on thermal performance. When the applied voltage increases, the hot side temperature incresing, while on the contrary of that appear on the cold side. This increasing the heat absorbed by the cold side as well as the heat rejected from the hot side, while the coefficient of performance decreasing with increasing applied voltage. The thermal resistance of heat sink is inversely proportional to the applied voltage. The increasing of heat sink fan speed has improved the system performance, where it leds to an increasing in heat absorbed by the cold side and the heat rejected from the hot side. Initial water temperature has a significant effect on the performance of TE water cooling system. The coefficient of performance equal to 0.14 when using initial water temperature of 15℃, while, it increase to be 0.5 when the initial water temperature increases to 30 ℃. That is happened due to the decrease in temperature gradient between cold side and hot side. Keywords: thermoelectric cooler, TEC, Peltier Effect, Coefficient-of-performance, heat sink.

In advance gas turbine, improve the thermal efficiency and power output it is require to increase turbine inlet temperature, that may be exceeds the melting point of the blade material, for that reason blade cooling technique is required. There are several methods have been suggested for cooling of the blades and one of this methods is to have radial holes to pass high velocity cooling air along the blade span. This paper is mainly focus on gas turbine blade heat transfer analysis and effect of increase number of external film cooling holes rows with internal film cooling holes on blade performance and select the optimum design with three different models consist of blade without holes and blades include (2, 3) external rows of film cooling holes with Specific number of internal cooling holes for both last two models. Results have been discussed and it is found that model-2 is the optimum solution, because of maximum total heat transfer rate and reduction in the blade leading edge temperature about 50% are attained in this model compared to model-1 and model-3, and it is found increase number of external film cooling holes rows in the blade not always lowers the blade leading edge temperature, sometimes leads to reheating process this depends on the design location of this holes on the blade surface. Steady state thermal analysis is carried out using CFD, Inconel 718 alloy selection as material and Nitrogen is used as a coolant.

The conjugate natural convection heat transfer in a partially heated square porous enclosure had been studied numerically. The governing dimensionless equations are solved using COMSOL Multiphysics and Darcy model assumed to be used. The considering dimensionless parameters are modified Rayleigh number, finite wall thickness, thermal conductivity ratio and the heat source length. The results are presented in terms of streamlines, isotherms and local and average Nusselt number. The results indicate that; the heat transfer can be enhanced by increasing the modified Rayleigh number. When the heat source length increases, the local Nusselt number of fluid phase increases, while, a reverse behavior of the local Nusselt number along the heat source is found. As the Rayleigh number increase, the local Nusselt number for both fluid and solid phase increases, therefore, the heat transfer rate will be enhanced. On the other hand, when the thermal conductivity ratio increase, the local Nusselt number for the fluid phase increases, and the local Nusselt number along the heated wall decreases.

Two-dimensional double-diffusive natural convective heat and mass transfer in an inclined rectangular porous medium has been investigated numerically. Two opposing walls of the cavity are maintained at fixed but different temperatures and concentrations; while the other two walls are adiabatic. The generalized model with the Boussinesq approximation is used to solve the governing equations. The flow is driven by a combined buoyancy effect due to both temperature and concentration variations. A finite volume approach has been used to solve the non-dimensional governing equations and the pressure velocity coupling is treated via the SIMPLER algorithm. The results are presented in streamline, isothermal, iso-concentration, Nusselt and Sherwood contours for different values of the non-dimensional governing parameters. A wide range of non-dimensional parameters have been used including, aspect ratio (2 ≤ A ≤ 5), angle of inclination of the cavity (0 ≤ ϕ ≤ 85), Lewis number (0.1 ≤ Le ≤ 10), and the buoyancy ratio (− 5 ≤ N ≤ 5).

Numerical unsteady predictions are carried out for two-dimensional natural convective heat transfer in a saturated porous square domain sandwiched between two finite wall thicknesses. The horizontal boundaries of the cavity are adiabatic and the vertical walls are maintained at fixed different temperatures T h and T c . In the core cavity (porous region), the extension of the Darcy model/Forchheimer–Brinkman-extended Darcy model with the Boussinesq approximation is used to solve the momentum equations as well as the energy and continuity equations. The conduction equation is employed to solve for the temperature distribution in the finite thickness wall layers. The nondimensional equations are solved by using the finite volume approach and the pressure velocity coupling is treated via the SIMPLE algorithm applicable in the porous media. The results are presented for different values of the nondimensional governing parameters, including the modified Rayleigh number (100 ≤ Ra* ≤ 1000), Darcy Number (10−7 ≤ Da ≤ 10−2), thermal conductivity ratio (0.1 ≤ Kr ≤ 10), and the ratio of wall thickness to height (0.1 ≤ D ≤ 0.4). A correlation to evaluate the average Nusselt numbers on the left wall interface of the porous cavity is proposed as a function of modified Rayleigh number, Darcy number, as well as a number of physical, geometrical and material property variables.

Steady conjugate double-diffusive natural convective heat and mass transfer in a two-dimensional variable porosity layer sandwiched between two walls has been studied numerically. The Forchheimer–Brinkman–extended Darcy model has been used to solve the governing equations in the saturated porous region. The flow is driven by a combined buoyancy effect due to both temperature and concentration variations. An exponential variation of the porosity near the hot wall is considered. The vertical walls are impermeable and subjected to a horizontal gradient of both temperature and concentration while the horizontal walls are adiabatic. A finite volume approach has been used to solve the dimensionless governing equations and the pressure velocity coupling is treated with the SIMPLE algorithm. The model has been validated with available experimental, analytical/computational studies.

Natural convection of a magneto hydrodynamic nanofluid in a porous cavity in the presence of a magnetic field is investigated. The two vertical side walls are held isothermally at temperatures Th and Tc, while the horizontal walls of the outer cone are adiabatic. The governing equations obtained with the Boussinesq approximation are solved using Comsol Multiphysics finite element analysis and simulation software. Impact of Rayleigh number (Ra), Hartmann number (Ha) and nanofluid volume fraction (ϕ) are depicted. Results indicated that temperature gradient increases considerably with enhance of Ra and ϕ but it reduces with increases of Ha.

Numerical study of natural convective heat transfer of partially heated tall rectangular cavity filled with (Al2O3-water) nanofluid. Two opposing horizontal walls are adiabatic, while the right vertical wall is kept at fixed cold temperature, and the left wall of the cavity heated partially. The effect of Rayleigh number (Ra), Aspect ratio (A), and the volume fractions of nanoparticles (ϕ) on the isotherms, streamline, and the average Nusselt number (Nu) have been investigated. The dimensionless governing equations with the Boussinesq approximation have been solved numerically, by using the finite element approach. The results presented for a wide range of parameters including; (103≤Ra≤105, 5≤A≤10, and 0.02≤ϕ≤0.06). The result shows that; the Nu increase when the effect of Rayleigh number (Ra), and the volume fractions of nanoparticles (ϕ) increasing, and also it increase when the Aspect ratio (A) increasing.

The present study, numerically investigated of mixed convection in a square enclosure with two layers, with Al2O3–water nanofluid (upper layer) and nano-porous medium (lower layer) with an adiabatic rotating circular cylinder at the center of the enclosure. The top and bottom walls are assumed adiabatic, while the left sidewall is heated, and the right sidewall kept cooled. Numerically, COMSOL code based on the Galerkin finite element method used for solved the dimensionless governing equations. The non-dimensional parameters that used in this study are: Rayleigh number (Ra) ranged from 103 up to 106, Darcy number (Da) equal to 10−3, the angular rotational velocity (Ω) ranged (0 and 6000), the solid volume fraction (ɸ=0.06), and the inner circular cylinder radius as (R = 0.2). The results showed that when Rayleigh numbers increase, a noticeable increase in the flow intensity and the steep temperature gradient, while the values increase when the cylinder rotates. The value of the local Nusselt number was high in the upper half of the cavity. The effect of the cylinder rotates is greater on the value of the local Nusselt number when using the low Rayleigh Numbers.

The present study, experimentally investigated the mixed convection in a square enclosure partitioned in two layers. The experiments were performed with Al2O3–water nanofluid (upper layer) and superposed porous medium (lower layer) with an adiabatic rotating cylinder at the center of the cavity. The boundary conditions of the experimental study were; the upper and lower walls were assumed adiabatic, the right wall was heated, and the left wall was cooled. Experimentally, 15 K-type thermocouples and thermal imaging camera were employed to measure the temperatures distribution inside the cavity when the concentration of nanoparticles (ɸ = 0.06), the temperature difference (∆T) between the cold and hot walls was (6, 8, and 10) °C, and angular rotational velocity (-50, -25, 0, 25, and 50) rpm. The results of experimental data showed that in general, the distribution of temperatures was very well along the upper half of the enclosure, while in the lower half the temperature distribution was confined near the hot wall region. When the circular cylinder rotates in counter-clockwise, it noted that the effect of speed is evident in the downside of the cylinder, while the temperature distribution in the left upper part of the enclosure decreasing. When the circular cylinder rotates in the clockwise direction, the results showed that the effect of cylinder rotation was around cylinder only. Moreover, the results demonstrated that the increasing temperature difference leads to a noticeable increment in the intensity of the flow.

The natural convection heat transfer has many applications in engineering like solar collectors, cooling of electronic equipment and geothermal engineering. The present work demonstrates the recent publications in the last ten years in this specific subject for a body located in complex shapes like rhombic, wavy, trapezoidal, elliptical and Parallelogrammic enclosure. Many parameters like Ra, Nu, number of undulations, the position of the inner body had been addressed and discuss to draw the main conclusions and recommendations. It is worthy to mention that wavy enclosure had been investigated less than the other simple enclosure shapes due to its complexity. Beside that entropy generation should be included in the future studies in complex shapes of enclosure as this will helps the researchers to extended their studies. The inner bodies inside trapezoidal, parallelogrammic enclosure are very limited and more investigation should be done.

In the old new present work cares with change of Reynolds number effect on the hydrodynamic characteristics. The different pitch angle is taken to analysis drag, lift, and pressure coefficients. The goal of these parameters is to understand the nature of the flow over the upper surface of the airfoil since the long laminar boundary layer and transition region have a light point for aerodynamics performance assessment. The results indicated that indicated the improvement in performance is parallel in path with the increasing length of the laminar flow region.

This paper presents a numerical simulation of MHD effects on laminar fluid flow throws a two-dimensional channel with an open cavity heated partially from the bottom with a constant length for the heated wall. A constant speed fluid flow (air) inters the horizontal channel at constant cold temperature and all the walls assumed to be insulated accept the heated wall at the bottom of the open cavity. In this study, COMSOL Multiphysics® Modelling Software (5.5) have been selected to solve the governing equations The results are carried out with a verity range of Richardson number and Hartmann number, while the Reynolds number and Prandtl number are kept constants (Re= 100, and Pr=0.707). The result shows that the heat transfer increases with increasing of the Richardson number, while it decreases with the increase of the magnetic field effects.

An experimental work has been investigated on a constant speed diesel engine using methyl ester waste cooking oil (MEWCO) and diesel. The biodiesel was prepared by transesterification process and mixed with original diesel with 10%, 20%, and 100% of MEWCO on volume basis. The impact of the blending ratio on performance, pollutant emissions as well as combustion parameters, were examined at variable load conditions. The results reported significant reduction in nitrogen oxides (NOx) and raising carbon emissions as well in all tested blend of MEWCO. 20% MEWCO is the recommended mixing percentage and above this ratio, noticeable reduction in the outcome of the performance has been observed. Symbol Definition and unit 10% MEWCO Blend ratio of 90 % diesel and 10 % MEWCO 20% MEWCO Blend ratio of 80 % diesel and 20 % MEWCO 100% MEWCO Blend ratio of 100 % MEWCO BTE Brake Thermal Efficiency (%) BSEC Brake specific energy consumption (MJ/kW.hr) BSFC Specific Consumption of Fuel (Brake) (g/kW.h) EGT Exhaust gas temperature (C) CA o Crank shaft angle (deg.) NOx Oxides of nitrogen (%) P Cylinder pressure (pa) HC Hydrocarbon emission (%)