22 May 2008

CO2 HEAT PUMP HEATING AND WATER HEATER SYSTEM FOR COLD AREA


By incorporating a first-stage expansion intermediate-cooling cycle (gas
injection) into a CO2 natural refrigerant heat pump, we have managed to achieve a significant
improvement in heating capacity and energy consumption efficiency under low ambient
temperature conditions. By combining this technology with previously fostered technologies
developed for CO2 heat pump application including the heater-less ice formation prevention
technology, the “direct heating” technology that provides direct heat exchange between the
CO2 refrigerant and heating antifreeze, and the outlet hot water temperature transition control
technology, we have developed a prototype of CO2 natural refrigerant heat pump heating and
water heater system, which enables both heating and hot water to be delivered by a single
system. This report describes the results obtained from performance evaluation tests
conducted in our environmental test laboratory and from monitoring tests in a cold region
(Hokkaido, Japan), and addresses the possibilities of this system for use in a heat pump
system application.