Zhili Lu, Guoliang Ding. Temperature and time-sharing running combination control strategy of two-circuit cycle refrigerator-freezer with parallel evaporators. Applied Thermal Engineering, 2006, 26: 1208-1217

Abstract: A two-circuit cycle refrigerator/freezer (RF) with parallel evaporators is more efficient than a single-loop RF and a bypass two-circuit cycle RF, and its cost is less than that of a dual-loop RF with two compressors. The existed control strategies for this kind of RFs are only based on the temperature control with FZC prior to FFC or FFC prior to FZC. When a lot of foods are put into FFC or FZC at a time, the compartment temperatures will go up very high and the food will be damaged. In order to solve this problem, the combination control strategy based on both the temperature control and the time-sharing running control is put forward in this paper. The rules to determine the maximum set on-time of FFC loop and that of FZC loop are presented based on theoretically analyses. The new control strategy is validated in a two-circuit cycle RF with parallel evaporators, and the compartment temperature fluctuations can be controlled within rational ranges under the conditions that a lot of food are put into FFC or FZC at a time, or the ambient temperature is very high. The daily energy consumption of the tested RF with the new control strategy is about 0.99% larger than that with the existed control strategies, which may be caused by the frequent shifts between FZC loop and FFC loop.
Keywords: refrigerator/freezer; control strategy; two-circuit; time-sharing; evaporators in parallel