Entropy generation analysis and dimensional optimization of an evaporator for use in a microscale refrigeration cycle

Entropy generation in the evaporator of a microscale vapor compression refrigeration cycle is investigated under the effects of vapor quality, mass and heat flux, saturation temperature, and channel dimensions. For a variety of channel heights and mass flow rates, the optimum vapor quality, and the channel and fin widths yielding minimum entropy generation are obtained. The variation of heat transfer coefficient with vapor quality, and pressure drop with heat flux compare very well with literature. The vapor quality yielding the minimum entropy generation is found as 0.846. The optimum channel and fin widths are 66 and 50 μm, respectively, for 700 μm channel height. Heat transfer is the major source of the total entropy production for 200-400 μm wide channels, while the contribution of pressure drop becomes comparable for narrower channels. The study is unique in the literature in pursuing an entropy generation minimization study for microscale two-phase flow.