Experimental Study on Automotive Cooling and Heating Air Conditioning System Using CO{sub}2 as a Refrigerant

摘要

This paper presents an experimental study on automotive cooling and heating air conditioning systems using CO{sub}2 as refrigerant. Recently as one of the countermeasures against the global warming and energy conservation problems, natural refrigerants such as CO{sub}2 are now paid attention as substitutes for HFCs in automotive air conditioning systems. Also, in recent years because the heat release from the eco-car's engine decreases, there is a problem that the present automotive heating air conditioning system can't provide sufficient heating capacity. Therefore an electric heater is now used as an auxiliary heating method, but it causes a decrease in the energy efficiency. Then we focused on the waste heat release of the heat pump cycle at the dehumidifying condition. By making use of the waste heat release as an auxiliary heating method in the place of the electric heat, we tried to develop a highly efficient automotive cooling and heating air conditioning system using CO{sub}2 as a refrigerant. In this study in order to increase the energy efficiency of this CO{sub}2 system the following measures were taken, 1) the construction of the CO{sub}2 heat pump system that use the heat release at the dehumidifying condition as the auxiliary heating method, 2) the examination of the optimal method to control the amount of the CO{sub}2 refrigerant held under both cooling and heating conditions, 3) the improvement of the elemental devices in CO{sub}2 heat pump cycle. As the result, a prototype of CO{sub}2 automotive cooling and heating air conditioning systems for medium-sized cars was successfully developed. With this system the performance better than that of the present HFC134a system can be achieved.