Entropy generation for flow boiling on a single semi-circular minichannel

Abstract

The paper investigates the effects of parameters such as mass flux, heat flux, channel diameter and inlet pressure on the entropy generation in flow boiling inside a semi-circular minichannel. A general entropy generation equation is derived for a single minichannel for flow boiling with developing flow, while also relaxing some heat transfer assumptions such as ΔTTsat≪1. The Romberg integration technique is used to solve for the entropy generation. Our results show that an increase in the mass flux causes an abrupt change in the entropy generation when the flow changes from laminar to transitional flow at small diameters although the effect is less significant at larger diameters. The heat transfer contribution in the entropy generation is also higher than the pressure drop contribution for the larger diameters. The larger channel diameters produce higher entropy generation compared to the smaller diameters for every heat flux investigated due to the increase in heat transfer contribution. An increase in the inlet pressure also decreases the entropy generation for every mass flux and heat flux. The aims of this study are to enhance the knowledge of the effects of heat transfer, pressure drop and flow behavior on the entropy generation, and to encourage researchers and designers to explore more novel features that can take advantage on the minimization of entropy generation.