Patent ID: 7992397

Claim:
An ammonia/CO 2 refrigeration system comprising: apparatuses working on an ammonia refrigerating cycle using ammonia; a brine cooler for cooling and condensing CO 2 by utilizing the latent heat of vaporization of the ammonia from the ammonia refrigeration cycle; a refrigeration load side cooler located at a higher gravitational level than the brine cooler; a supply line for supplying the cooled and liquefied CO 2 from the brine cooler to the refrigeration load side cooler; a return line for returning CO 2 from the refrigeration load side cooler to the brine cooler; a liquid pump provided in the supply line, the liquid pump being a variable-discharge pump that forcibly circulates CO 2 between the brine and refrigeration load side coolers, and having a discharge capacity that is equal to or greater than twice the circulation flow required by the refrigeration load side cooler to evaporate CO 2 in a liquid or liquid/gas mixed state (imperfectly evaporated state) to allow the brine cooler to recover CO 2 in the liquid state or liquid/gas mixed state; a controller that controls CO 2 recovery by controlling circulation volume of the CO 2 circulated by the liquid pump to maintain the CO 2 returning from the refrigeration load side cooler in the liquid or liquid/gas mixed state; and a CO 2 gas return passage connecting the refrigeration load side cooler to the brine cooler or to a liquid reservoir provided downstream of the brine cooler with respect to a flow direction of the refrigerant, wherein the CO 2 gas return passage is provided separately from the return line for returning excess CO 2 gas to the brine cooler or the liquid reservoir to liquefy the returned CO 2 gas in the brine cooler or the liquid reservoir and reduce CO 2 pressure when the pressure in the load side cooler is equal to or higher than a predetermined value.