COMPUTER MODELING AND PREDICTION OF PERFORMANCE OF AN AIR SOURCE HEAT PUMP WITH A CAPILLARY TUBE

An analysis of the vapor compression cycle and the main components of an air source heat pump during steady state operation has been performed with emphasis on fundamental phenomena taking place between key locations in the refrigerant system. The basis of the general heat pump model formulation is the logic which links the analytical models of heat pump components together in a format requiring an iterative solution of refrigerant pressure, enthalpy and mass balances.; The modeling effort emphasis was on the local thermodynamic phenomena which were described by fundamental heat transfer equations and equation of state relationships among materials properties. In the compressor model several refrigerant locations were identified and the processes taking place between these locations accounted for all significant heat and pressure losses. Evaporator and condenser models were developed on a tube-by-tube basis where performance of each coil tube is computed separately by considering the cross-flow heat transfer with the external air stream and the appropriate heat and mass transfer relationships. A capillary tube model was formulated with the aid of Fanno flow theory.; The developed heat pump model has been validated by checking computer results against laboratory test data for full and part load operation for the cooling/dehumidifying mode as well as the heating mode under frosting conditions.