MEASUREMENT AND MODELLING OF ICE RINK HEAT LOADS

Abstract: Ice rinks are among the most energy intensive public buildings in developed and developing countries. According to a research on Swedish ice rinks; a typical ice rink consumes approximately 1185 MWh/year which leads to more than 300 GWh/year for the 342 Swedish indoor ice rinks. The refrigeration system is usually the largest consumer by 43% average share of the total energy consumption.  To decrease the refrigeration system energy demand, there are a variety of energy efficiency techniques known and available but the key to select the best ones is finding the major heat loads on the ice sheet and refrigeration system, which is unique for each ice rink. To fulfil this objective and in addition to review literature, this study has two main approaches. The first approach is to measure and evaluate the performance of the refrigeration system in two ice rinks, called Norrtälje and Älta. The estimated cooling capacity is approximately equal to the total heat load on the ice plus the heat gains in the distribution system. This goal has been accomplished by using a performance analyser called “ClimaCheck” which is based on an “internal method” because it uses the compressor as an internal mass flow meter and consequently, there is no need for an external one. The refrigerant mass flow rate is calculated by an energy balance over the compressor. By knowing the mass flow, enthalpy of the refrigerant, etc. the cooling capacity and COP of the system can be calculated. While the total heat load is known by the first approach, the second approach tries to discover different heat loads shares by analytical modelling. The measured physical and thermodynamical parameters plus the ice rink geometrical characteristics are input to the heat transfer correlations to estimate the heat load magnitude. The results of the measurements show that the total energy consumption in Norrtälje is about two third of Älta. The main reasons for this less energy consumption are smarter control systems for compressors and pumps, better ventilation distribution design and 1°C-2°C higher ice temperature.      Analytical modelling for a sample day has estimated that about 84% of the total heat loads is originated from the heat loads on ice sheet while the distribution system causes the remaining 16%. Moreover, calculations show that convection plus small portion of condensation (altogether 36%), radiation (23%), ice resurfacing (14%) and lighting (7%) are the largest heat loads in winter while in summer condensation is another significant heat load (10%). Comparing two six-hour periods, one without ice resurfacing and four resurfacings in the second one, 30% more cooling demand has been calculated for the second period. Furthermore, it has been shown that the evaporator to brine is the contributor for 66% of the heat transfer resistances from ice to evaporator while brine to bottom ice and bottom to top ice accounts for 27% and 7% respectively. To conclude, a parallel “performance analysis of the refrigeration system” and “heat loads estimation” proves to be a useful tool for adopting proper design and control for energy efficient operation.