Entropy generation due to mixed convection between vertical parallel plates under isothermal boundary conditions

2009 ◽  
Vol 6 (5) ◽  
pp. 671 ◽  
Author(s):  
Esmail M.A. Mokheimer ◽  
Ali Hassan Al Salim
Keyword(s):  
Boundary Conditions ◽  
Mixed Convection ◽  
Entropy Generation ◽  
Parallel Plates ◽  
Isothermal Boundary

Entropy Generation Analysis of Mixed Convection Flow in a Nanofluid Filled Porous Cavity Using a Two-Component Lattice Boltzmann Method

2019 ◽  
Author(s):  
Dhrubajyoti Kashyap ◽  
Anoop K. Dass
Keyword(s):  
Heat Transfer ◽  
Boundary Conditions ◽  
Mixed Convection ◽  
Entropy Generation ◽  
Lattice Boltzmann ◽  
Lattice Boltzmann Model ◽  
Convection Flow ◽  
Mixed Convection Flow ◽  
Two Phase ◽  
Good Concordance

Abstract In the present work, a comprehensive analysis is made to understand the effect of velocity boundary conditions on the flow and thermal behaviour during mixed convection flow in a nanofluid-saturated porous square cavity. Two different velocity boundary conditions based on the movement of horizontal walls of the cavity are considered. The vertical fixed walls are differentially heated and the horizontal lids are thermally insulated. We have adopted the two-phase thermal lattice Boltzmann model (TLBM) for nanofluid system and modified this model to simulate nanofluid-filled porous medium by incorporating the Brinkman–Forchheimer-extended Darcy model. The current results provide good concordance with the published results computed through conventional numerical techniques. The detailed study of the heat transfer rate, entropy generation is made for discretely varying Richardson numbers (Ri) from 0.1 to 10 and Darcy numbers (Da) from 10−4 to 10−2 while maintaining Grashof number (Gr) at 104 and volume fractions of Cu nanoparticle (ϕ) less than equal to 5%. It is observed from the results that the optimal flow condition in terms of energy efficiency depends on the values of Ri and Da. From the viewpoint of both 1st and 2nd laws of thermodynamics, the performance of nanofluid is not satisfactory compared to the base fluid for current configurations as the augmentation of entropy generation with ϕ is more prominent compared to heat transfer enhancement.

Mixed Convection and Entropy Generation Characteristics Inside a Porous Cavity With Viscous Dissipation Effect

2009 ◽  
Author(s):  
A. K. M. Sadrul Islam ◽  
M. Ruhul Amin ◽  
Shama F. Barna ◽  
Arafat A. Bhuiyan ◽  
M. H. Banna
Keyword(s):  
Nusselt Number ◽  
Aspect Ratio ◽  
Boundary Conditions ◽  
Mixed Convection ◽  
Entropy Generation ◽  
Average Energy ◽  
Forced Flow ◽  
Convection Flow ◽  
Bejan Number ◽  
Left Wall

This paper examines and explains two-dimensional, steady mixed convection flow in a porous square vented cavity. The interaction between the buoyancy stemming from one or more heated elements inside a microstructure filled vented enclosure and an imposed forced flow forms the topic of this investigation. Analysis has been carried out for two different boundary conditions. Initial investigations are carried out for walls of the enclosure being isothermal. A second stage of analysis is performed keeping only the left wall isothermal and other three walls adiabatic. Natural convection takes place due to temperature difference between the isothermal wall and the fluid. Forced convection condition is imposed by providing an inlet and a square vent inside the enclosure filled with fluid saturated porous medium. The mathematical model is developed using modified Darcy flow model and energy equation. Through the adaptation of the well known finite element method, solution to this numerical problem is obtained. Governing parameters chosen are Peclet Number (Pe), Rayleigh Number (Ra), Aspect ratio (AR) and the width of the inlet as a fraction of the width (I/W) of the enclosure. For detailed analysis different value of these parameters such as five Rayleigh Numbers (1, 50, 100, 500 and 1000) and seven different Peclet Numbers (0.1, 1, 5, 10, 20, 50 and 100) are considered. Effect of inlet to cavity width ratio is examined within the range 0.1 ≤ I/W ≤ 0.5 for a particular aspect ratio. The performance of the enclosure in both cases; are determined by flow visualization and by analyzing different parameters such as Bejan Number, Nusselt Number and Entropy Generation Number. Isotherms, streamlines show substantial variation in their pattern or magnitude. Average Nusselt number and average Bejan Number increases whereas Average energy flux density decreases with increasing I/W. These fluctuations also vary for different Rayleigh or Peclet numbers. The results for both the boundary conditions are also compared to find the most effective value of I/W.

Numerical Simulation of Boundary Conditions Effect on Heat Transfer and Entropy Generation in a Square Cavity Filled with Al2O3-Cu -Water Hybrid Nanofluid

2021 ◽  
Vol 406 ◽  
pp. 98-109
Author(s):  
Ilhem Zeghbid ◽  
Rachid Bessaih
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Boundary Conditions ◽  
Mixed Convection ◽  
Heat Transfer Rate ◽  
Entropy Generation ◽  
Transfer Rate ◽  
The Other ◽  
Hybrid Nanofluid ◽  
Different Boundary Conditions

A numerical simulation was performed in four geometries with different boundary conditions; two geometries have top walls moving with a constant horizontal velocity U0 in two opposite directions, while the other geometries have vertical walls moving in two opposite directions with a constant vertical velocity V0. These cavities are filled with hybrid nanofluid Al2O3-Cu/water, and heated by two constant flow heat sources placed on the left vertical wall. The moving wall and the other walls are respectively maintained at a local cold temperature Tc. The interest of this work is to see the effects generated by incorporation of hybrid nanofluids on the mixed convection flow, and to make an analysis of the entropy production in the mixed convection problem in order to be able to choose the geometry with different boundary conditions among the four geometries with different boundary conditions that will ensure energy efficiency. The finite volume method was used to solve the heat transfer flow equations across the physical domain with the SIMPLER algorithm. The influence of relevant parameters such as Richardson and Reynolds numbers and volume fraction of nanoparticles on entropy generation and heat transfer rate were studied. It was found that entropy generation decreases with increasing Richardson number, Reynolds number and that incorporation of a hybrid Al2O3-Cu/water nanofluid in the base fluid improves the high heat transfer rate.

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