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Solid-Vapor Sorption Refrigeration Systems
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Complex compound sorption reactions are ideally suited for use in refrigeration cycles as an economically viable alternative to CFC refrigerants. Complex compound refrigeration provides a number of energy-saving advantages over present refrigeration systems beyond the elimination of CFCs. The elimination of moving parts in complex compound equipment lowers maintenance cost. Also, when ammonia is used as the refrigerant, the replacement of the compressor by the complex compound allows for direct modular integration into existing refrigeration plants. The availability of waste heat at a user's site allows for the further potential of substantially reduced energy costs. To use complex compounds in a commercial refrigeration cycle, several criteria must be met: 1. Practical reaction rates must be achievable with economical heat exchanger hardware. 2. Reactions must proceed without the need for excessive driving temperatures or large pressure differences. 3. A significant fraction of the coordination sphere of the complex compound (refrigerant sorption capacity) must be useable. 4. The compounds must be stable and the adsorption/desorption must be repeatable over a large number of cycles. 5. Compounds with appropriate vapor pressures for the particular refrigeration temperature must be available. Recent investigations conducted at Rocky Research on the reactivities, coordination, vapor pressure, stability, availability, and cycleability of a large number of complex compounds have shown that, through the use of proprietary heat exchanger configurations, all of these criteria can readily be met. We have achieved rates of reaction which are nearly an order of magnitude faster than have been reported using conventional means employed in zeolite and activated carbon cycles. Reaction rates have been measured for refrigeration cycles down to -70°F and found to be satisfactory for commercial use. The achievement of refrigeration at almost any desired firing-reject-cooling temperature combination is possible either through proper selection of the complex compound or through staging of several complex compounds. Cost estimates show appreciable savings over electric drive systems, the savings increasing as the refrigeration temperature is lowered. In this paper we present data for a single effect complex compound refrigeration cycle. Realistic estimates of COP, first cost, operating costs, and payback time are made for a typical commercial installation.
Graebel, W.; Rockenfeller, U.; Kirol, L. (1991). Solid-Vapor Sorption Refrigeration Systems. Energy Systems Laboratory (http://esl.eslwin.tamu.edu). Available electronically from