Microchannels have become a hot issue in heat exchanger research. In this paper

the microchannel evaporator with CO2 was taken as research subject. A new entropy mathematical model was proposed for microchannel evaporator with CO2 flowing inside and air flowing outside. Phase transition existed on both sides. Entropy generation number Ns represented the losses due to temperature difference of heat transfer and pressure drop. A steady state distributed parameter model for the microchannel evaporator was established to solve entropy generation number. Comparisons of analytical and existing experimental data were made to verify and validate the model. The effects of mass flow rate of CO2 and air

CO2 evaporation temperature and inlet air temperature on system entropy generation number were analyzed. The results from the mathematic model showed that mass flow rate of CO2 had little effect on system entropy generation number. System entropy was mostly caused by temperature difference of heat transfer between CO2 and air sides. With rising inlet air temperature

entropy generation number became larger. While with rising CO2 evaporation temperature

system entropy generation number decreased. With increasing air mass flow rate

system entropy generation number increased. The higher the evaporation temperature

the greater the impact of air mass flow rate on system entropy generation number.