Gas-Liquid Distributions of Refrigerant Flows in Multi-pass Channels with Vertical Headers

－Comparison of Gas-Liquid Distributions and Pressure Losses Measured with R410A and R134a－

Abstract

An experimental study was conducted on gas-liquid distribution characteristics of the refrigerant two-phase flow in a multi-pass channel with vertical headers and horizontal multiport flat tubes, which simulated the parallel-flow type evaporator used in residential and commercial air conditioners. In particular, two kinds of refrigerants with different operating pressures, R410A and R134a, were used in the experiment to examine the influence of properties of the refrigerant on the gas-liquid distribution and pressure loss characteristics of the channel. Although the vapor density of R134a was about half that of R410A, no significant difference was observed in the flow in the inlet header. As a result, the liquid distribution characteristics of R134a agreed quantitatively with those of R410A. On the other hand, the pressure loss of the test channel increased by 20% - 80% with R134a in comparison with R410A. This larger pressure loss of the test channel for R134a was mainly caused by the increase of the frictional pressure loss in branch tubes.