Influence of Lubricating Oil on Heat Pump Performance
The aim of this work is to extend the investigation, to the influence of lubricating oil on R22-oil mixture in the heat pump and refrigeration system. The refrigerant-oil test bed was modified to accommodate R22-oil mixture investigation and R22-oil solubility equation was developed. The influence of oil on evaporator heat transfer coefficient, refrigerant and water side heat, pressure drop and evaporator coefficient of performance was investigated. The results of this work show that, evaporator performance degraded or upgraded depending on the oil concentration and evaporator outlet temperature.The study of the evaporator heat pick up data shows that the addition of different percentages of oil at various evaporating temperature resultls in reduction of heat pick up by the evaporator and this is pronounced at higher oil fraction and lower evaporating temperature. It is concluded that, combination of oil fraction and the evaporator outlet temperature are two dominant factors in degrading the evaporator performance. The evaporator performs less well at high oil fraction and low evaporator outlet temperature. Furthermore,introduction of oil into the evaporator had an effect on the two phase flow pattern inside the evaporator and the region of two phase flow extended to the entire evaporator tubes.