Practical Aspects of Ammonia Water as Secondary Refrigerant in Ice Rinks

The transition from fluorinated gases to natural refrigerants could be key to reducing the impacts of climate change. Ice rinks are energy-intensive buildings, with large heating and cooling demands. The pumping power required to move the secondary refrigerant typically accounts for a sizable amount of the energy use of the refrigeration system. The use of aqua ammonia as a secondary fluid shows promising results, with pumping power use of about half that required of ethylene glycol, environmental friendliness, and low corrosivity to steel components. Aqua ammonia is still novel but is currently in use in 34 Swedish ice rinks. This thesis addresses questions regarding evaporation rates, performance, material compatibility, safety, and regulations of aqua ammonia in ice rink systems. Laboratory tests were performed to assess aqua ammonia evaporation rates during storage and operations. Long-duration concentration change, in well-sealed and well-stored containers, indicated low levels of evaporation for all tested concentrations samples. Short-term concentration in open-air conditions, indicated rapid rates of evaporation, with nearly full evaporation of all ammonia concentration occurring within only 90 seconds of open-air exposure. Testing of sample-mixtures containing contamination by substances aqua ammonia was likely to encounter during retrofit replacement situations determined that aqua ammonia and calcium chloride produce flakey sedimentation. Additionally, lower concentrations of aqua ammonia are slightly more prone to becoming basic when mixed with the tested substances, such as calcium chloride. Historical data of systems operating with aqua ammonia were analyzed for energy performance. While pumping requirements typically account for 10-20% of the energy for refrigeration, the pumps of the rinks studied with aqua ammonia accounted for only 1.2 to 4.2%. However, data availability and system configuration anomalies suggest additional analyses are required. Furthermore, best operating, maintenance, and safety practices were analyzed and global regulatory restrictions were examined. Surveying of manufacturer material compatibility information found copper and brass to be incompatible with aqua ammonia, while steel and carbon steel are recommended. Various plastics were addressed by the manufacturers, notably PVC was found to be acceptable for use with aqua ammonia. A cost comparison between aqua ammonia and calcium chloride found aqua ammonia to require less expensive equipment. Finally, aqua ammonia was determined to fall outside of the classification of refrigerants in several international refrigeration codes. Various additional safety regulations guiding personal protective equipment, exposure times, transportation, storage, and disposal regulations were catalogued as part of this work. In summary, aqua ammonia was found to be a safe substance with performance that matches theoretical energy savings. Pumping requirements were reduced from 10-20% to approximately 1-5% of overall refrigeration system energy use. Necessary safety precautions were found to be much less stringent than high concentrations of ammonia and aqua ammonia was ascertained to fall outside of refrigeration codes in Europe, Canada, and the United States of America

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