Entropy analysis of nanofluid convection in a heated porous microchannel under MHD field considering solid heat generation

Abstract

Present study analyzes the issue of entropy generation of water with Al2O3 nanoparticles in a horizontal porous microchannel heated symmetrically. 2D distribution of temperature in both phases are derived using two-energy-equation model. An analytic investigation is carried out and the parameters of magnetohydrodynamic (MHD) field, solid heat generation and symmetric thermal condition are explored thoroughly. The results revealed that the MHD field noticeably affects the distribution of temperature and velocity and as an output the heat transfer irreversibilities during the process. The solid and fluid heat transfer irreversibilities for the case under MHD field are lower than those of the case without it, which proves the advantages to MHD field in declining the heat transfer irreversibility. Then, it was obtained that when Ha number is constant and Reynolds number has the optimum value of 6.5, total entropy generation is minimum and it decreases when MHD is intensified at Reop. Also MHD was effective merely when the value of Reynolds number was lower than the critical value. By applying heat generation to the solid, for the MHD cases, no significant changes were observed in MHD irreversibility, however, entropy generation of the solid was achieved to be the most effective parameter and the value of total irreversibility increased noticeably. The analysis of thermal equilibrium and non-equilibrium models and the differences in irreversibilites showed that the increments in suspension of nanoparticles reduced the deviation between the two models, and intensification of Ha number at low biot numbers further reduces it.