PURPOSE: To increase the capacity and efficiency of the title device by a method wherein the refrigerant inlet ports for low-stage and high-stage of a refrigerant heat exchanger are connected to first and second throttle devices and the refrigerant outlet port for low-stage is connected between first and second non-return valves and a throttle device while a refrigerant outlet port for high-stage is connected to an intermediate point between a low-stage side compressing mechanism and a high-stage side compressing mechanism.
CONSTITUTION: Upon heating operation, the refrigerant of a load side heat exchanger 4 is branched through first throttle devices 5 and a first non-return valve 11 and refrigerant for low-stage flows from a refrigerant/refrigerant heat exchanger 9 into a heat source side heat exchanger 7 through a fourth non-return valve 14 and a second throttle device 6 while refrigerant for high-stage flows to an intermediate point between a low-stage side compressing mechanism 1 and a high-stage side compressing mechanism 2 through an auxiliary throttle device 10 and the refrigerant/refrigerant heat exchanger 9. Upon cooling operation, the refrigerant of a heat source side heat exchanger 7 is branched through the second throttle device 6 and a second non-return valve 12 and refrigerant for low-stage flows from the refrigerant/ refrigerant heat exchanger 9 into the load side heat exchanger 4 through a third non-return value 13 and the first throttle devices 5 while the refrigerant for high-stage flows to an intermediate point between compressing mechanisms 1, 2 through the refrigerant/refrigerant heat exchanger 9. According to this method, the circulating amount of refregerant is increased and the capacity as well as the efficiently of the title device can be increased.
NAKATANI KAZUO
FUNAKURA SHOZO
TAGASHIRA MINORU
