Gas-liquid flow distribution uniformity parameters in upward multi-pass compact evaporator

Abstract

The gas-liquid flow distributions in multi-pass upward parallel channels that simulate the evaporator for the automobile air-conditioner system were examined experimentally. In this paper, the attentions are (1) To study the influences of the backpressure condition at the branch outlets and of the flow-inlet condition at the header entrance on the gas-liquid distributions to the branches, (2) To discover the most influenced parameter to the flow distribution uniformity by using design of experiment method. Experiments were conducted in an isothermal air-water flow system. The influence of the backpressure condition on the flow distributions changed depending on the flow-inlet condition. In the stratified-flow inlet, the backpressure condition was highly influential in both the air and water distributions, and the uniform water distribution that was ideal for the evaporators could not be achieved even if air was distributed uniformly to all branches. In the mist-flow inlet, the water distribution was insensitive to the backpressure conditions and its uniformity was improved in comparison with that in the stratified-flow inlet. The flow distribution uniformity for gas phase is influenced mostly by superficial air velocity, and the flow distribution uniformity of liquid phase is mostly influence by 2-way interaction of parameters which are flow pattern and superficial air velocity.