Heat pump air conditioner for use in cold districts

摘要

The invention provides a heat pump air conditioner using air as a heat source which can operate for heating even at the temperature of outdoor air lower than -15 DEG C. A scroll compressor (1), a four-way valve (2), an indoor heat exchanger (101), a receiver (7), an outdoor refrigerant control valve (4), and an outdoor heat exchanger (3) are connected in sequence by pipes. A bypass flow line for injecting a liquid refrigerant into the scroll compressor is arranged between a receiver (7) and the scroll compressor through a liquid injection refrigerant control valve (6). The scroll compressor is variable in rotational speed and is operated at a high speed under control by a rotational speed controller for thereby achieving a high heating capability. Even when the temperature of outdoor air is lower than -15 DEG C, particularly at around -20 DEG C, the heat pump air conditioner can develop a heating capability comparable to that developed when the temperature of outdoor air is 0 DEG C. The cost required for the heat pump air conditioner to effect heating and cooling is comparable to the cost required for an air conditioner which employs kerosene for heating and a refrigeration cycle for cooling. From trial calculation in terms of primary energy, it has proved that the inventive heat pump air conditioner consumes less energy than the conventional one. <IMAGE>