Optimal Thermodynamic Parameters of Two-Phase Ejector Refrigeration System for Buses

Abstract Air-conditioning is necessary for the comfort of passengers in commercial buses. However, installing an air-conditioning system can add extra load on the engine and result in extra fuel cost. Therefore, an improvement in the air-conditioning system can lower the fuel consumption of the buses and reduce the size of the evaporator and the condenser. It is known that using two-phase ejector as an expansion valve in the air-conditioning system can improve the system performance. This study offers a model to predict the optimal thermodynamic parameters for a two-phase ejector refrigeration system for buses using R134a under various operating conditions. An empirical correlation is derived to determine the optimal thermodynamic parameters of the system. The effect of evaporation and condensation temperatures on the heat transfer surface area are discussed and graphically illustrated. Moreover, an experimental study to validate the developed model has been carried out in a midibus air-conditioning system. The study findings revealed that the heat transfer surface area can be reduced by about 4% and 55% in the condenser and evaporator, respectively.

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