Theoretical And Experimental Study On The Performance Of An Air-Conditioner Under Variable Conditions

In this paper a steady distributed parameter model for refrigeration system of an air-conditioner was presented and a simulation program was developed by using finite difference method to predict the steady performance of the refrigeration system under the variable conditions. The influences of the inlet air temperature of the condenser and evaporator, as well as the face velocity through the condenser and evaporator was discussed. The split phase flow model is used in the heat exchanger models and the effects of the heat exchanger tubes arrangement on the inlet air paraments were considered. In the capillary tube the homogeneous model is employed and the delay of the flash point and the choked flow were included.In order to verify the validity of the mathematical models and the calculation method, a series of experiments on the performance of an air-conditioner under variable conditions was conducted in the psychrometric rooms.The performances of the proto type under the different inlet air temperature of the condenser and evaporator, as well as the different face velocity of the condenser and evaporator was measured. The calculational and experimental results indicate that evaporation pressure, supercooling and superheat degree, refrigerating capacity and COP increase with the increase of face velocity and inlet air temperature of the evaporator, but condensation pressure nearly constant. With the increase of inlet air temperature of the condenser, evaporation pressure, condensation pressure increase, but supercooling and superheat degree, refrigerating capacity and COP decrease. The experimental results indicate that there's a critical face velocity, when the face velocity of the condenser is lower than this critical velocity, the performance of the system and refrigerating capacity change rapidly with the face velocity of the condenser, and when the face velocity of condenser is higher than this critical velocity, the influence of the face velocity of the condenser on the performance of the system is gradually diminish. It has the utility value to choose the appropriate face velocity of the condenser in the design of air-conditioner system.