Performance of a commercial ice pond refrigeration system for long-term potato storage (part 2): cooling performance

摘要

This report describes the cooling performance of a commercial-scale refrigeration system with an ice pond of 1200 m-3 capacity which was designed and built at Tokachi, Hokkaido, to store 180 metric tons of potatoes until next July following the harvest. The storage area was filled with about 50 metric tons of potatoes which were refrigerated from the end of March using about 1000 M-3 ice produced in the winter. The maximum cooling power of the system was 13.3 kW and the cooling COP (coefficient of performance) was about 1.7. The storage environment remained favorable for potatoes at 2 deg C and 93 percent relative humidity until the end of May. From the beginning of June, the cooling system was continuously operated until mid-August prior to the disappearance of ice at the end of August. An electric cooler was also used during this period due to the rising outside temperature and the increased frequency of door opening and closing. Since dehumidification was minimal in the ice pond refrigeration, the storage area naturally remained at high relative humidity obviating the need for a humidifier. The pre-cooling experiment with asparagus and cabbage yielded good results. The heat transfer through the top surface of the massive ice constituted a major portion of the total heat load responsible for melting the ice compared with that from the bottom and the sides. The measured amount of the total heat load on the ice mass agreed fairly well with the estimated value obtained from the initial latent heat of fusion stored in the manufactured ice.