24 June 2014

SECONDARY FLUID IMPACT ON ICE RINK REFRIGERATION SYSTEM PERFORMANCE


Sweden has 352 ice rinks in operation which annually use approximately 1000MWh. A refrigeration system usually accounts for about 43% of the total energy consumption and can
present a significant energy saving potential. More than 97% of the Swedish ice rinks use indirect refrigeration system and thermo-physical properties of secondary fluid have a direct impact on the heat transfer and pressure drop. A theoretical model and two case studies
focusing on the importance of the secondary fluid choice were investigated. The results showed that potassium formate had the best heat transfer properties while ammonia lead to the lowest pressure drops and pumping power. Propylene glycol showed the worst performance in both cases. Ammonia and potassium formate showed respectively 5% and
3% higher COP than calcium chloride for typical heat loads of 150kW. When controlling the pump over a temperature difference (?T), the existence of the optimum pump control or optimum flow was highlighted. For typical cooling capacity of 150kW optimum pump control temperature difference ?T was around 2,5K for calcium chloride and around 2K for
ammonia. Järfälla case study showed a potential energy saving of 12% for the refrigeration system when increasing the freezing point of the secondary fluid. An energy saving of around
10,8 MWh/yr per 1K increase of the secondary fluid freezing point was found.