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Photovoltaic thermal (PV/T) collectors that supply both electricity and heat are growingly becoming popular in household and other applications. However, efficient heat removal from backside of PV module is still a challenge that hampers its electrical as well as thermal performance. In the present research, an absorber-plate less thermal collector has been introduced and mathematical model of such a PV/T system has been developed, which is employed in COMSOL Multiphysics® software to simulate the heat transfer phenomenon in the system. Effect of different flow parameters on heat transfer and PV/T performance is thus studied numerically in the developed simulation model. Also, the effect of irradiation level and depth of the flow channel has been examined on the thermal as well as electrical performance of the module. Results reveal that PV/T electrical and thermal efficiency increase with both of Reynolds and Prandtl number. Heat transfer rate is observed to increase as high as 25.5% with increasing Reynolds number. A maximum reduction in cell temperature of 10.2 °C is obtained by increasing the channel depth. Elimination of absorber plate from thermal collector simplified the design reducing its weight and cost as well.

The paper executes the laminar natural convection flow and heat transfer inside a prismatic enclosure with non-uniform temperature distribution maintained at the bottom wall. The side walls are insulated and the remaining walls are cooled at temperature T c . A magnetic field of strength B 0 is applied horizontally normal to the side walls. The water- Al 2 O 3 nanofluid is used as the heat transfer medium through the enclosure. Finite Element Method of Galerkin's weighted residual scheme is used to solve the transport equations with appropriate boundary conditions. The effect of Hartman number Ha (0 to 50) for nanofluid as well as for the base fluid on isotherms, streamlines and heat lines, local and average heat transfer are presented graphically. The calculations have been performed for Prandtl number Pr = 6.2. Results indicate that the heat transfer rate is significantly affected by increasing the mentioned parameter.

In the present study, double-diffusive natural convection flow inside a window shaped cavity containing multiple obstacles filled with nanofluid is studied numerically. Water base nanofluid containing various nanoparticles including Ag, Cu and Al 2 O 3 are considered as working fluid. The left and right inclined walls of the cavity are maintained at a relatively low temperature and low concentration while the vertical walls are adiabatic and impermeable. The non-uniform temperature and concentration are imposed along the bottom wall of the cavity. The governing equations are transformed to the dimensionless form and solved numerically using Galerkin weighted residual technique of finite element method. The influence of pertinent parameters such as thermal Rayleigh number and Lewis number and volume fraction of nanoparticles on the heat and mass transfer and fluid flow is studied. The results are obtained in terms of streamlines, isotherms, isoconcentrations, average Nusselt number and average Sherwood number for the considered parameters and it is observed that the flow pattern, temperature and concentration fields are affected by the variation of the parameters.

A study of natural convective flow, heat transfer and entropy generation in an odd-shaped geometry is presented here. The geometry considered is a combination of the horizontal and vertical enclosure shapes. The cavity is filled with Cu–water nanofluid. The numerical study focuses specifically on the effect of natural convection parameter and solid volume fraction of nanoparticle on the average Nusselt number, total entropy generation and Bejan number. Also isotherms, stream function and entropy generation due to heat transfer are presented for various Rayleigh number and solid volume fraction. The governing equations are solved by using penalty finite element method with Galerkins weighted residual technique. The results reveal that increasing Rayleigh number causes increase of the average Nusselt number as well as the heat transfer term of entropy generation and decrease of the viscous term. The proper choice of Rayleigh number could be able to maximize heat transfer rate simultaneously minimizing entropy generation.

Sustainable energy generation is one of the most important challenges facing society today. Solar energy is one of the best sources of renewable energy with minimal environmental impact which offers a solution. The present work investigates the heat transfer performance and entropy generation of forced convection through a direct absorption solar collector. The working fluid is Cu–water nanofluid. The simulations focus specifically on the effect of solid volume fraction of nanoparticle and Reynolds number on the mean Nusselt number, mean entropy generation, Bejan number and collector efficiency. Also Isotherms and heatfunction are presented for various solid volume fraction and inertia force. The governing partial differential equations are solved using penalty finite element method with Galerkins weighted residual technique. The results show that both the mean Nusselt number and entropy generation increase as the volume fraction of Cu nanoparticles and Reynolds number increase. The results presented in this study provide a useful source of reference for enhancing the forced convection heat transfer performance while simultaneously reducing the entropy generation.

Forced convective flow and heat transfer by different nanofluids through a flat plate solar collector is analyzed numerically by this article. The solar collector has the flat-plate cover and sinusoidal wavy absorber. Four different nanofluids like water-Ag nanofluid, water based Cu nanofluid, water-Al2O3 nanofluid and water-CuO nanofluid are used as the operational fluids inside the solar collector. The governing partial differential equations with proper boundary conditions are solved by Finite Element Method using Galerkin's weighted residual scheme. The behavior of different nanofluids related to performance such as temperature and velocity distributions, radiative and convective heat transfers, mean temperature and velocity of the nanofluid is investigated systematically. This performance includes the solid volume fraction namely ϕ with respect to above mentioned nanofluids. The results show that the better performance of heat transfer inside the collector is found by using the highest ϕ of water based Ag nanofluid.

A numerical investigation is presented for the natural convective flow and thermal behaviors of nanofluid inside a complicated enclosure due to Prandtl number variation. The cavity consists of a centered heated diamond shaped hollow obstacle. The vertical walls are constantly and uniformly less heated than the obstacle. The bottom surface of the cavity is adiabatic. The upper horizontal part of the enclosure is surrounded by solid material with constant thermal conductivity. The upper boundary of this solid region is considered as adiabatic. The working fluid is water based nanofluid having copper nanoparticles. The governing equations are solved numerically using Galerkin's Weighted Residual Finite Element method. Results are presented in the form of average Nusselt number, average temperature, mean velocity of the nanofluid, mid height horizontal and vertical velocities for a selected range of viscosity parameter Pr (4.2 – 8.8). Streamlines and isothermal lines are also displayed for the above mentioned parameters. The results show that the increment in Pr enhanced the rate of heat transfer.

Natural convection heat transfer from a heated cylinder contained in a square enclosure filled with water–Cu nanofluid is investigated numerically. The main objective of this study is to explore the influence of pertinent parameters such as Prandtl number (Pr) and diameter (D) of the heated body on the flow and heat transfer performance of nanofluids while Rayleigh number (Ra) and the solid particle volume fraction (ϕ) of nanoparticle are considered fixed. The results obtained from finite element method clearly indicate that heat transfer augmentation is possible using highly viscous nanofluid resulting in the compactness of many industrial devices.

This work is focused on the numerical modeling of steady laminar natural convection flow in an annulus filled with water–alumina nanofluid. The inner surface of the annulus is heated uniformly by a uniform heat flux q and the outer boundary is kept at a constant temperature T c . Two thermal conductivity models namely, the Chon et al. model and the Maxwell Garnett model, are used to evaluate the heat transfer enhancement in the annulus. The governing equations are solved numerically subject to appropriate boundary conditions by a penalty finite-element method. A parametric study is conducted and a selective set of graphical results is presented and discussed to illustrate the effects of the presence of nanoparticles, the Prandtl number and the Grashof number on the flow and heat transfer characteristics for both nanofluid models. It is found that significant heat transfer enhancement can be obtained due to the presence of nanoparticles and that this is accentuated by increasing the nanoparticles volume fraction and Prandtl number at moderate and large Grashof number using both models. However, for the Chon et al. model the greatest heat transfer rate is obtained.

The present paper implements the analysis of magnetohydrodynamic (MHD) combined convective flow and heat transfer characteristics through a triangular wavy vertical channel using the Galerkin weighted residual finite element method. The flow enters at the bottom and exits from the top surface. The wavy vertical walls are at constant temperature and the cold flow enters the channel from the inlet. The numerical model is based on a 2D Navier–Stokes incompressible flow and energy equation. The effects of Grashof number, Reynolds number and Prandtl number on flow and thermal fields are investigated. The variation of local Nusselt number along the vertical walls for the mentioned parameters is also presented. The study reveals that the flow as well as thermal field strongly depends on the aforesaid parameters.

A numerical study has been executed to analyze the effects of Reynolds and Prandtl number on mixed convective flow and heat transfer characteristics inside a ventilated cavity in presence of a heat-generating solid circular obstacle placed at the center. The inlet opening is at the bottom of the left wall, while the outlet one is at the top of the right wall and all the walls of the cavity are considered to be adiabatic. Galerkin weighted residual finite element method is used to solve the governing equations of mass, momentum and energy. Results are presented in terms of streamlines, isotherms, the average Nusselt number, the Drag force and the average fluid temperature in the cavity for different combinations of controlling parameters namely, Reynolds number, Prandtl number and Richardson number. The results indicate that the flow and thermal fields as well as the heat transfer rate, the Drag force and the average fluid temperature in the cavity depend significantly on the mentioned parameters.

A numerical study is conducted to investigate the transport mechanism of free convection in a trapezoidal enclosure filled with water–Cu nanofluid. The horizontal walls of the enclosure are insulated while the inclined walls are kept at constant but different temperatures. The numerical approach is based on the finite element technique with Galerkin's weighted residual simulation. Solutions are obtained for a wide range of the aspect ratio (AR) and Prandtl number (Pr) with Rayleigh number (Ra = 105) and solid volume fraction (ϕ = 0.05). The streamlines, isotherm plots and the variation of the average Nusselt number at the left hot wall are presented and discussed. It is found that both AR and Pr affect the fluid flow and heat transfer in the enclosure. A correlation is also developed graphically for the average Nusselt number as a function of the Prandtl number as well as the cavity aspect ratio.

The present numerical simulation is conducted to analyze the mixed convection flow and heat transfer in a lid-driven cavity with sinusoidal wavy bottom surface in presence of transverse magnetic field. The enclosure is saturated with electrically conducting fluid. The cavity vertical walls are insulated while the wavy bottom surface is maintained at a uniform temperature higher than the top lid. In addition, the transport equations are solved by using the finite element formulation based on the Galerkin method of weighted residuals. The implications of Reynolds number (Re), Hartmann number (Ha) and number of undulations (λ) on the flow structure and heat transfer characteristics are investigated in detail while, Prandtl number (Pr) and Rayleigh number (Ra) are considered fixed. The trend of the local heat transfer is found to follow a wavy pattern. The results of this investigation illustrate that the average Nusselt number (Nu) at the heated surface increases with an increase of the number of waves as well as the Reynolds number, while decreases with increasing Hartmann number.

The development of magnetic field effect on mixed convective flow in a horizontal channel with a bottom heated open enclosure has been numerically studied. The enclosure considered has rectangular horizontal lower surface and vertical side surfaces. The lower surface is at a uniform temperature T h while other sides of the cavity along with the channel walls are adiabatic. The governing two-dimensional flow equations have been solved by using Galarkin weighted residual finite element technique. The investigations are conducted for different values of Rayleigh number ( Ra ), Reynolds number ( Re ) and Hartmann number ( Ha ). Various characteristics such as streamlines, isotherms and heat transfer rate in terms of the average Nusselt number ( Nu ), the Drag force ( D ) and average bulk temperature ( θ av ) are presented. The results indicate that the mentioned parameters strongly affect the flow phenomenon and temperature field inside the cavity whereas in the channel these effects are less significant.