Quasi-steady state model of an ice rink refrigeration system

Abstract

A quasi-steady model for the refrigeration system of an indoor ice rink was developed based on a combination of thermodynamic relations, heat transfer correlations and data available in the manufacturer’s catalogue. The system includes five compressors, rejects heat to the ambient air and uses R-22 to keep a stream of brine at a temperature of approximately −9°C. The model has been validated by comparison with measured values and with data from the manufacturer’s catalogue. It was then used to simulate its performance over a typical meteorological year. Results for a representative day include the number of compressors in operation at any given moment, their power consumption, the coefficient of performance (COP) of the cycle and of the system, as well as the heat rejected by the condensers and the corresponding mass flow rate of the cooling air. They show that the evaporation pressure is essentially constant while the condensation pressure varies from about 1600 to 2000 kPa. The COP of the system varies between 1.9 and 2.5. Results for the entire year show that the heat rejected during phase change is approximately four times that due to desuperheating and demonstrates the interest of recovering heat from both processes. Finally, the model is used to illustrate the advantages of a control strategy which limits the maximum number of simultaneously operating compressors to four. This strategy results in a 10% decrease of the energy used by the compressor motors and a 20% decrease of the peak power demand but increases the temperature of the brine at the exit from the chillers by approximately 0.5°C during short periods following the ice resurfacing operations.