Abstract

An experimental study was conducted on gas-liquid distributions of the refrigerant flow in a multi-pass channel with vertical headers and horizontal multiport flat tubes that simulated the parallel-flow type evaporator. In particular, the influence of protrusion of branch tubes into the dividing header on gas-liquid distributions and pressure loss of the channel was examined. The refrigerant (R410A) was supplied from the bottom of the header, and experiments were conducted under an adiabatic condition. It was found that the maximum height of the liquid distribution was increased by protruding branch tubes into the header at high mass flow rates. The pressure loss of the channel increased as the mass flow rate and/or quality of the refrigerant were increased, and the pressure loss in branch tubes occupied 60-70% of the pressure loss of the channel. The pressure in the dividing header decreased gradually in the upward direction, while that in the combining header was almost constant. Based on experimental data, we made clear pressure distributions in channels. The pressure in the channel showed quite a uniform distribution in the vertical direction under a high quality condition, while the uniformity of the liquid distribution was deteriorated as the quality was increased.