DEVELOPMENT OF MULTI-FUNCTION CO2 HEAT PUMP WATER HEATER
We have succeeded in the development of a hot water supply system with a highefficiency heat pump using a natural refrigerant (CO2), and also succeeded in its massproduction for the first time in the world in 2001.After the first product launch, we have developed a multi-function type, which can be used as a floor-heater and bathroom-heater in addition to the hot water supply. During development, there was a difficulty that the efficiency decreased due to the temperature rise of water returned from the heater. However, we have solved this problem with our ejector cycle technology and the technology of the cascade heat process, which makes it possible to use the hot water in the storage tank for hot water supply or heater selectively. Then, we commercialised this multi-function type in 2003.In this paper, we are reporting the “multi-function CO2 heat pump water heater” characterized by the ejector cycle technology and the technology of the cascade heat process.