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Refrigerant And Lubricant Charge In Ac Heat Exchangers: Experimentally Validated Model, Shenghan Jin, Predrag S. Hrnjak

International Refrigeration and Air Conditioning Conference

The paper presents a semi-empirical model to predict refrigerant and lubricant inventory in both microchannel condenser and plate-and-fin evaporator of an air conditioning system. In the model, heat exchanger is discretized into finite volumes. Temperature, pressure and mass inventory are calculated by applying heat transfer, pressure drop and void fraction correlations to these volumes respectively. Refrigerant and lubricant are treated as a zeotropic mixture with a temperature glide. As refrigerant evaporates or condenses, thermophysical properties are evaluated accordingly with the change of lubricant concentration. Oil is assumed to be retained in refrigerant oil mixture at concentration that is changing during …