Entropy generation analysis for forced convection boiling in absorber tubes of linear fresnel reflector solar thermal system

Abstract

A methodology has been presented related to entropy generation due to forced convection boiling in long absorber tubes used in linear Fresnel reflector solar thermal system. Variable heat flux has been applied on the tube which replicates the scenario for aforementioned tubes and local entropy generation has been obtained for various parameters. Mathematical modeling has been made separately for single-phase and two-phase regions in flow boiling conditions encountered in linear Fresnel reflector tubes. Entropy generation in two-phase region has been formulated using homogeneous equilibrium model. The entropy generation at varying mass flux and heat flux cases are calculated. The entropy generation due to heat transfer is found to be more than that of pressure drop. Still, entropy generation due to pressure drop in two-phase region plays a major role of increasing nature of it. Present approach will help researchers and industry to optimize the solar thermal systems where flow related phase change occurs and measures can be taken accordingly to increase energy efficiency of those systems.