Performance Evaluation of Prototype Microchannel Evaporators for the Residential Air-Conditioning Application

Abstract

The present study was aimed to evaluate the performance of prototype microchannel evaporators for the residential air-conditioning application using R-22 refrigerant under wet condition. Eight prototype evaporators were manufactured and tested using psychrometric calorimeter test facilities. Each evaporator consisted of two or three parallel flow heat exchangers connected with return pipes. The parallel flow heat exchanger had 41 parallel microchannel tubes that brazed into the inlet and outlet headers. The tube had 8 rectangular ports with the hydraulic diameter of 1.3 mm. The louvered fin had louver angle of 27°, louver pitch of 1.4 mm and flow depth of 18.8 mm. It was found that the flow area ratio had a great effect on the cooling capacity of the microchannel evaporator from experimental results of prototypes 4, 5 and 6, and there was an appropriate range for cooling capacity. The flow distribution characteristics were slightly affected by the pressure drop resulting from the configuration of the refrigerant flow at the exit of the evaporator like merging manifold, which means that it could be possible to reduce the manufacturing cost of the microchannel evaporator. Both refrigerant and air-side pressure drops for the best prototype evaporator were 28.6 kPa and 2.53 mmAq, respectively, which could be affordable for the residential air-conditioning application.