Numerical study of surface radiation-natural convection entropy generation in a 2D cavity using the LBM

Abstract

This paper investigated the surface radiation-natural convection heat transfer with entropy generation in a 2D rectangular cavity. Also, the effects of Ra and ε were analyzed on radiation entropy generation (REG), conduction entropy generation (CEG), and fluid flow friction entropy generation (FEG). For problem simulation, energy and momentum equations were solved by the lattice Boltzmann method (LBM), and thermal radiation was investigated using the surface radiation method with gray surfaces. The top and the bottom walls are adiabatic, and the sidewalls are at a constant temperature. Simulations were conducted for Ra = 104, 105, and 106, and ε = 0, 0.5, 0.8, and 1. Results show that REG has a symmetrical distribution on the constant temperature walls and the cold wall has the most REG. Higher REG and lower CEG are the consequence of increasing ε, furthermore, both of them increase by increasing Ra and vice versa. FEG has the lowest value of entropy generation for all Ra and can be neglected, therefore Be is very close to 1 in all cases. In addition, conduction (for ε=0, and 0.5) and radiation (for ε=0.8, and 1) have the most entropy generation. Generally, The total entropy generation (TEG) increases with increasing Ra and ε.