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In the present study, the flow field and heat transfer of a water–copper nanofluid with variable properties in a trapezoidal enclosure saturated with porous media are studied. The governing equations are solved by finite volume method and the SIMPLER algorithm. The nanofluid flow is assumed to be laminar, steady and incompressible. Simulations are performed for sidewall (trapezoid legs) angles of 30°, 45° and 60° with respect to horizontal axis, Reynolds numbers from 10 to 1000, Darcy numbers of 10−2, 10−3, 10−4 and volume fractions of 0 to 0.04 of nanoparticles. Numerical results show that the average Nusselt number increases with increasing volume fraction of nanoparticles for all studied Darcy numbers. The convection and motion of the nanofluid decrease by reducing the Darcy number which leads to a reduction in the velocity and local Nusselt number. The average Nusselt number increases by increasing the Darcy number for all aspect ratios. Also, the average Nusselt number increases with increasing Reynolds number for all Darcy numbers, aspect ratios and volume fractions of nanoparticles.

The present study aims at nanoparticles characterization and stability as well as the thermal conductivity of the hybrid nano-oil of ZnO–MWCNT/oil at the temperature range from 25 to 65 °C and the concentrations range from 0.50 to 3.2% for the solid particles. First, the nanoparticles of MWCNT and ZnO were characterized using XRD-FESEM and FTIR tests, and according to the results, the analysis of atomic, surface and chemical structure of nanoparticles was made. The nanolubricant was prepared by a two-step method. For this purpose, firstly, the stability was analyzed by the DLS test and the results show that the nanoparticles are in nanoscale after the construction of nano-oil. The thermal conductivity was measured based on the variables of temperature and volume fraction. An increasing trend was observed for the thermal conductivity for higher temperature and volume fraction of the nanoparticles. The biggest improvement of the thermal conductivity compared to the base fluid is at 65 °C, the volume fraction is 3.2%, and its value is 35.1%. Moreover, a very accurate experimental relationship was developed to determine the ratio of the thermal conductivity of nano-oil in the empirical range.

The opposing flow in a porous medium refers to a condition when the forcing velocity flows in opposite direction to thermal buoyancy obstructing the buoyant force. The present research refers to the effect of opposing flow in a vertical porous annulus embedded with fluid saturated porous medium. The thermal non-equilibrium approach with Darcy modal is considered. The boundary conditions are such that the inner radius is heated with constant temperature Tw the outer radius is maintained at constant temperature Tc. The coupled nonlinear partial differential equations such as momentum equation, energy equation for fluid and energy equation for solid are solved using the finite element method. The opposing flow variation of average Nusselt number with respect to radius ratio Rr, Aspect ratioAr and Radiation parameter Rd for different values of Peclet number Pe are investigated. It is found that the flow behavior is quite different from that of aiding flow.

A numerical study based on the finite volume method has been performed to study the three-dimension natural convection in a parallelogrammic top side opened cavity filled nanofluid with partially heated square at the bottom side. Results are obtained for different governing parameters such as nanoparticle concentration (φ) from 0 to 0.05, inclination angle of the back and front walls (α) from 5° to 75°, Rayleigh number from 103 to 105, and length of heater changer from 0.1 to 1. The main finding from the obtained result showed that the inclination angle and nanoparticle volume fraction affect the flow structure and enhance the heat transfer.

Present study deals with the analysis of heat transfer and fluid flow behavior in an annular cone fixed with saturated porous medium. The inner surface of the cone is assumed to have power law variable wall temperature. The governing partial differential equations are solved using well known Finite Element Method (FEM). The coupled nonlinear differential equations are converted into the algebraic equations by using Galerkin method. A 3 noded triangular element is used to divide the porous domain into smaller segments. The effects of various geometrical parameters on the cone angle are presented. It is found that the effect of cone angle on the heat transfer characteristics and fluid flow behavior is considerably significant. The fluid moment is found to shift towards the upper side of cone with increase in the power law coefficient. The fluid velocity decreases with increase in the power law coefficient.

The present study is intended to study heat and mass transfer in a vertical annular cylinder embedded with saturated porous medium. The inner surface of cylinder is maintained at uniform wall temperature and uniform wall concentration. The governing partial differential equations are non-dimensionalised and solved by using finite element method (FEM). The porous medium is discritised using triangular elements with uneven element size. Large number of smaller-sized elements are placed near the walls of the annulus to capture the smallest variation in solution parameters. The results are reported for both aiding and opposing flows. The effects of various non-dimensional numbers such as buoyancy ratio, Lewis number, Rayleigh number, aspect ratio, etc on heat and mass transfer are discussed. The temperature and concentration profiles are presented.

Conjugate heat transfer is an important area of research which has been in demand due to its applications related to various scientific and engineering fields. The current research is focused to study the heat transfer in a porous medium sandwiched between two solid walls of an annular vertical cylinder. The prime focus of the current study was to evaluate the effect of solid wall thickness, the influence of variable wall thickness at inner and the outer radius, the conductivity ratio and the solid wall conductivity ratio on the heat transfer characteristics of the porous medium. The surface at inner and outer radii of the annulus is maintained isothermally at T h and T ∞ such that T h > T ∞ . The governing partial differential equations for the conjugate heat transfer in porous medium and that of solid walls are converted into a set of algebraic equations with the help of finite element method and then solved simultaneously to predict the temperature variation in the solid wall as well as the porous region of the annular domain.

Numerical simulation of the natural convection and entropy generation in an air-filled cubical cavity with active lateral walls is performed in this work. Both the lateral front and right sidewalls are maintained at an isothermal cold temperature. While an isothermal hot temperature is applied for both the lateral back and left sidewalls. The upper and lower walls are kept adiabatic. Entropy generation rates due to the fluid friction and the heat transfer are simulated by using the Second law of thermodynamics. Results are illustrated for Rayleigh numbers varied from (103 ? Ra ? 106). It was shown that the increase in the Rayleigh number leads to increase the average Nusselt number and to decrease the Bejan number. Also, it was found that both, Sth, and Stot, increase slightly with the increase in Rayleigh number until they reach (Ra = 105) and then begin to jump after this value. After (Ra = 105), the increase in both, Stot, and Sfr, is greater than Sth. Moreover, it was observed that iso-surfaces of Stot are similar to Sth at (103 ? Ra ? 105), while they are similar to Sfr at high Rayleigh number. nema

Effect of magnetic field on combined surface tension and buoyancy convection in an enclosure with partially active vertical walls is investigated numerically. The active part of the left side wall is at a higher temperature than the active part of the right side wall. The bottom and the inactive parts of the side walls are adiabatic and capillary forces occur at the top free surface. The governing equations are discretized by the finite volume method. The results are obtained for Pr = 0.054, 0 ? Ha ? 100, 0 ? Ma ? 10000, and 2.104 ? Gr ? 2.106. The flow structure and temperature field were presented by streamlines and isotherms respectively. The surface tension effect of is manifested by increasing Marangoni number. The application of magnetic field was found to control the flow and to oppose the capillary effects. nema

Purpose The purpose of this paper is to highlight the advantages of a simplified algorithm to solve the problem of heat and mass transfer in porous medium by reducing the number of partial differential equations from four to three. Design/methodology/approach The approach of the present paper is to develop a simplified algorithm to reduce the number of equations involved in conjugate heat transfer in porous medium. Findings Developed algorithm/method has many advantages over conventional method of solution for conjugate heat transfer in porous medium. Research limitations/implications The current work is applicable to conjugate heat transfer problem. Practical implications The developed algorithm is useful in reducing the number of equations to be solved, thus reducing the computational resources required. Originality/value Development of simplified algorithm and comparison with conventional method.