Influences of Channel Attitudes on Air-Water Flow in an Evaporator Flat Channel with a Sharp 180-Degree Turn.

Abstract

An experimental study has been conducted on air-water two-phase flows in a flat channel with a sharp 180-degree turn which simulates the refrigerant channel of an evaporator for an automobile air-conditioning system. Attention has been directed to the influences of channel attitudes on two phase flow characteristics such as local void fraction and pressure drop. Five channel attitudes have been tested here ; [U] : The channel is set vertically in the shape of a "U". [RU] : Upside-down of [U]. [TF] : The channel is set in the shape of a "C" and fluids are fed from the upper entrance. [BF] : Fluids are fed from the lower entrance of the "C"-shape channel attitude. [H] : The channel is set horizontally. Uniform liquid film flow, which is favorable in the heat-transfer performance of the evaporator, is obtained in the channel attitudes of [RU] and [H]. The pressure loss is higher in [U] and [BF] under the condition of low quality. Irrespective of the channel attitudes, the pressure loss in the present test channel can be well expressed by the modified Lockhart-Martinelli correlation. From the results of the experiments, it has been found that the channel attitude of [RU] is the most favorable for the evaporator refrigerant channel.