Development of a microchannel evaporator model for a CO2 air-conditioning system

This paper presents the development and verification of a heat exchanger mo del for evaluating the thermal performance of an evaporator for a CO2 mobil e air-conditioning system. The model has been developed, on the basis of th e finite volume method, with emphasis placed on the air-side heat and mass transfer processes. The governing equations are derived from mass and energ y balances using the newly developed air-side heat transfer and friction lo ss correlations for microchannel heat exchangers under both dry and wet con ditions. The calculated air-side heat transfer and pressure drop data are i n good agreement with measured data. However, the refrigerant-side pressure drop estimation for microchannel tubes usually underestimates the measured value. The simulation results and importance of selecting appropriate heat transfer and pressure drop correlations for the microchannel heat exchange r are addressed. (C) 2001 Elsevier Science Ltd. All rights reserved.