Distribution Characteristics and Optimization on Parallel Flow Microchannel Heat Exchanger

The uneven distribution of refrigerants in parallel flow microchannel heat exchangers is one of the reasons that limit their further promotion and application. When the parallel flow microchannel heat exchanger is used as an evaporator, the refrigerant at the inlet of the evaporator is in a vapor-liquid two-phase state, which causes an uneven distribution of vapor and liquid refrigerant in the evaporator. In this study, a two-phase R134a refrigerant was used as the working fluid, and a numerical simulation model which was verified by previous experimental data was proposed. Four schemes to improve the refrigerant distribution characteristics by changing the protrusion depth of different flat tubes are proposed. Numerical simulation models were used for the calculation. When the mass flow rate is 100 kg/(m2?s) and the refrigerant quality is 0.4, it is found by changing the protrusion depth of different flat tubes in the header, the liquid phase refrigerant distribution characteristics can be improved by 29.4%–52.4%.