Simplified explicit calculation algorithms for determining the performance of refrigerant coils in vapour-compression systems

Abstract

Simplified explicit calculation algorithms were proposed for determining the performance of the condenser, evaporator and air cooler in a vapour-compression system based on a zone-model approach. It was assumed that the fluid temperature changes in the sub-cooled and superheated portions were small and that the wet portion of an air cooler only occurred in the entire saturated portion if it was not fully-dry. With R134a employed as the refrigerant, the simulated coil capacity based on the present modelling approach were compared with those based on a multi-node numerical approach at different refrigerant mass flow rates. It was found that the errors in the simulated specific enthalpy change of the refrigerant across the coil did not exceed 3.6% in all cases. In particular, the errors incurred by employing the present modelling approach in simulating the capacity and compressor power input of a sample water-cooled chiller at different condenser and evaporator fluid entering temperatures were less than 2.7% and 3.1% respectively. This showed that the present approach could be a good choice for improving the computation efficiency of a vapour-compression system significantly while the accuracy of the simulation could still be maintained at an acceptable level.