IRREVERSIBILITY ANALYSIS OF AN EVAPORATOR FOR USE IN A MICRO-REFRIGERATION CYCLE

This study aims to investigate the entropy generation in the evaporator component of a microscale vapor compression refrigeration cycle (MVCRC). The evaporator design plays an important role in attaining high COP’s in the cycle, and devising the smallest possible structure. MVCRC is an alternative electronics cooling system gaining popularity due to its ability to remove high heat fluxes. The second law analysis is widely used in designing thermal systems. It gives the opportunity of evaluating the contributions of heat transfer and pressure drop for entropy generation in microchannel heat sinks, such as the evaporator of a MVCRC. Rectangular copper microchannels have been considered, and R-134a is used as the refrigerant. The effects of mass flux, saturation temperature, channel dimensions, and heat flux on entropy generation are investigated. Using two phase models available in the literature, a mapping study giving entropy generation values for various parameters is conducted. Adiabatic fin tip analysis is employed to find the base temperature which is important when calculating the entropy generation due to heat transfer. The domain is divided into segments for the accurate calculation of the entropy generation as the fluid properties vary due to the pressure drop in the flow direction. Widely accepted micro-scale empirical correlations are used in the calculations. The study is thought to be useful in terms of handling a variety of parameters in two phase refrigerant flow.