International agreements have legislated the phaseout of many refrigerants, including R502 and R12, which are commonly used in supermarket refrigeration systems. R22 and ammonia (R717) are candidate replacement refrigerants having appropriate thermodynamic properties. The toxicity of ammonia at low concentrations requires that it be confined to the equipment room, so a secondary fluid is needed to distribute cooling to the refrigerated cases. Investigates ammonia-secondary fluid systems and compares their performance with equivalent R22 systems. Both R22 and ammonia have high compressor discharge temperatures, necessitating staged compression. Three methods of staging the compression were compared for both refrigerants. Six secondary fluids were evaluated for use with ammonia in the supermarket system. The overall system performance of the ammonia-secondary fluid refrigeration system, including both compressor and secondary fluid pump power, is governed by a large set of design parameters. The influence of these parameters on the overall system performance was studied in a systematic manner. From this parametric study, design rules leading to optimal ammonia-secondary fluid systems were developed. The performance of well-designed ammonia-secondary fluid systems was found to be 4% to 10% lower than that of R22 systems operating under similar conditions.

KEYWORDS: year 1995, ammonia, secondary, fluids, supermarkets, refrigeration, freezers, R22, refrigerants, replacing, compression refrigeration, comparing, performance, designing, propylene, heat flow, measuring, heat transfer fluids