Experimental study on gas-liquid flow distributions in multi-pass channels.

An experimental study was conducted on gas-liquid flow distributions in a multi-pass channel with horizontal headers and downward-flow branches. The refrigerant flowing in branch tubes was evaporated by heating tube surfaces to simulate a real operating condition of the evaporator. The gas-liquid flow visualized under the heated condition was compared with the adiabatic flow. Moreover, temperatures on branch surfaces were measured to estimate liquid distributions to branches, and they were compared with water distributions measured in the isothermal air-water flow. The refrigerant-flow characteristics in the dividing header under the heated condition were quite different from those observed under the adiabatic condition. The temperature distributions on branch surfaces were consistent with water distributions measured in the air-water flow. This suggests that the liquid distribution characteristics of the refrigerant flow under the heated condition can be simulated qualitatively by water distributions in the isothermal air-water flow.