An experimentally validated modeling of refrigerant distribution in a parallel microchannel evaporator

This paper describes modeling of two phase flow distribution in a microchannel evaporator, on the basis of the pseudo 2-D finite volume method. Emphasis is placed on refrigerant-side heat transfer and pressure drop characteristics. The global flow distribution is based on the mechanistic fact that the pressure drop along each flow path containing an individual microchannel tube must be the same. Both the primary pressure drop across the microchannel tube and minor pressure drops are included. This model simulates refrigerant distribution in a microchannel evaporator for two cases. Firstly, flash gas generated in the expansion valve is separated and only single phase liquid is supplied into the evaporator; the second case is a conventional direct expansion operation where refrigerant in two-phase state is directly fed into the evaporator. Mass flow rate and quality in each microchannel tube, overall pressure drop and evaporator surface temperatures are obtained and then compared to data taken from the experimental facility, and good agreement is attained for the experimental and predicted data.