Experimental study was performed for oil circulation effects on evaporation heat transfer in the brazed type plate heat exchangers using R134A. In this study, distribution device was installed to ensure uniform flow distribution in the refrigerant flow passage, which enhances heat transfer performance of plate type heat exchanger. Tests were conducted for three evaporation temperature; 33℃, 37℃, and 41℃ and several oil circulation conditions. The nominal conditions of refrigerant are as follows: inlet vapor quality at evaporator is 0.2, and degree of superheat at the evaporator outlet is maintained by 5℃. The heat transfer correlation of water-side was developed by modifed Wilson plot method. The evaporation heat transfer coefficient can be obtained from the definition of overall heat transfer coefficient using developed water-side heat transfer correlation. The plate heat exchanger with distribution device shows enhanced heat transfer coefficient by 8% compared with that of conventional plate heat exchanger. The oil circulation effects on evaporation heat transfer coefficient were analyzed, and the heat transfer performance variations were presented depending on evaporation temperature, refrigerant flow rate and oil circulation.
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