Lanterna Rally

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Published: 1978

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A prototype ice-maker heat pump obtained from Remcor Products Company and a two-plate unit developed at Oak Ridge National Laboratory were tested under the Annual Cycle Energy System program. Results were compared for the effect of harvesting scheme and evaporator plate loading on performance in both water-chilling and ice-making modes. The Remcor scheme of using compressor discharge gas for harvesting exacts a heavy penalty on performance during short freeze cycles, whereas the two-plate unit utilizing a no-penalty harvest scheme experiences no such penalty. However, the lower plate loading of the Remcor gives it a performance advantage over the two-plate unit in water chilling and allows it to operate on a longer freezing cycle before suffering performance penalties due to ice buildup. This latter effect allows the Remcor to overcome its harvest penalty and to achieve a slightly higher maximum coefficient of performance in the ice-making mode than does the two-plate unit. Accordingly, it is concluded that a combination of no-penalty harvest and low plate loading should provide a more optimum performance level for ice-maker heat pumps. Cyclic operation, typical of domestic space conditioning operation, of the two-plate unit revealed significant performance loss due to interrupted compressor operation. The possibility of improving operation and reliability by combining thermostatic cycles with harvesting cycles is discussed and a possible scheme presented.