Entropy Generation Minimization Analysis of Passive and Active Magnetocaloric Regenerators
A numerical study is presented on the performance optimization of passive and active magnetocaloric regenerators using entropy generation minimization. The mathematical model consists of the Brinkman-Forchheimer equation and energy equations to describe the fluid flow and the heat transfer in the fluid and solid phases of the regenerator. Based on the velocity and temperature profiles, local rates of entropy generation per unit volume were integrated to give the cycle-average entropy generation in the regenerator, which is the objective function of the optimization procedure. The solid matrix is a bed of spherical particles (stainless steel in the passive and gadolinium in the active regnerator) and the working fluid is water. Performance evaluation criteria of fixed cross-section (face) area and variable geometry are incorporated into the optimization procedure to identify the most appropriate parameters and operating conditions under fixed constraints of specified heat transfer effectiveness (passive regenerator) and cooling capacity (active regenerator).