Air-conditioning apparatus and method for controlling the same

Abstract

When operation of an air-conditioning apparatus starts, an operation determination means determines whether the operation is a cooling operation or a heating operation. If the operation is determined not to be the cooling operation, a discharge gas cooling unit does not perform cooling. On the other hand, if the operation is determined to be the cooling operation, the discharge gas cooling unit cools discharge gas.

1 . An air-conditioning apparatus including a refrigerant circuit in which a compressor, a discharge gas cooling unit, an oil separator, a flow switching device, an indoor heat exchanger, an expansion valve, and an outdoor heat exchanger are connected to each other in a loop and capable of performing a cooling operation and a heating operation by switching a channel with the flow switching device, the air-conditioning apparatus comprising:
 a heat rejection control means for controlling the discharge gas cooling unit such that
 the discharge gas cooling unit cools discharge gas from the compressor when the operating state is the cooling operation, and 
 the discharge gas cooling unit does not cool the discharge gas when the operating state is the heating operation. 
   
     
     
         2 . The air-conditioning apparatus of  claim 1 , wherein
 the heat rejection control means has a function of detecting an operating frequency of the compressor, and   the heat rejection control means controls the discharge gas cooling unit such that
 the discharge gas cooling unit cools the discharge gas when the operating state is the cooling operation and the operating frequency detected by the heat rejection control means is greater than or equal to a predetermined operating frequency, and 
 the discharge gas cooling unit does not cool the discharge gas if the operating frequency detected by the heat rejection control means is less than the predetermined operating frequency. 
   
     
     
         3 . The air-conditioning apparatus of  claim 1 , wherein
 the discharge gas cooling unit includes
 a pump that circulates a circulation substance, 
 a heat rejecter that is connected to the pump and performs heat rejection from the circulation substance, and 
 a heat exchanger that is connected to the heat rejecter and the pump and exchanges heat between the circulation substance and the discharge gas, and 
   the heat rejection control means controls the discharge gas cooling unit such that
 the pump is driven to cool the discharge gas in the heat exchanger in the cooling operation, and 
 driving of the pump is stopped so as not to cool the discharge gas in the heat exchanger in the heating operation. 
   
     
     
         4 . The air-conditioning apparatus of  claim 1 , wherein
 the discharge gas cooling unit includes
 a heat exchanger including a refrigerant channel in which the discharge gas from the compressor flows and a cooling channel connected to a suction-side pipe of the compressor such that suction gas to be sucked in the compressor flows into the cooling channel, and 
 a first three-way valve having two ports connected to the suction-side pipe of the compressor and one port connected to an outflow-side end of the cooling channel of the heat exchanger, and 
   the heat rejection control means controls the first three-way valve such that
 the suction gas circulates in the cooling channel of the heat exchanger so as to cool the discharge gas in the cooling operation, and 
 a flow of the suction gas into the cooling channel of the heat exchanger is stopped so as not to cool the discharge gas in the heating operation. 
   
     
     
         5 . The air-conditioning apparatus of  claim 1 , wherein
 the outdoor heat exchanger includes an air supply unit,   the discharge gas cooling unit includes a heat rejecter connected between a discharge-side pipe of the compressor and the oil separator, and a damper disposed between the heat rejecter and the air supply unit and capable of opening and closing such that an air supply from the air supply unit is shut or passed, and   the heat rejection control means controls the damper such that
 the damper is opened so as to cause the air supply from the air supply unit to strike the heat rejecter and cool the discharge gas in the cooling operation, and 
 the damper is closed so as to shut the air supply from the air supply unit to the heat rejecter and not to cool the discharge gas in the heating operation. 
   
     
     
         6 . The air-conditioning apparatus of  claim 1 , wherein
 the discharge gas cooling unit includes a pump that circulates a circulation substance, a heat rejecter that is connected to the pump and performs heat rejection from the circulation substance, a heat exchanger that is connected to the heat rejecter and the pump and exchanges heat between the circulation substance and the discharge gas, and a second three-way valve having two ports connected between a discharge-side pipe of the compressor and a suction-side pipe of the heat exchanger and one port connected between the discharge side of the heat exchanger and an inlet of the oil separator, and   the heat rejection control means controls the second three-way valve such that
 the discharge gas passes through the heat exchanger and is cooled in the cooling operation, and 
 the discharge gas does not pass through the heat exchanger and is not cooled in the heating operation. 
   
     
     
         7 . A method for controlling an air-conditioning apparatus including a refrigerant circuit in which a compressor, a discharge gas cooling unit, an oil separator, a flow switching device, an indoor heat exchanger, an expansion valve, and an outdoor heat exchanger are connected to each other in a loop and capable of performing a cooling operation and a heating operation by switching a channel with the flow switching device, the method comprising:
 controlling the discharge gas cooling unit such that   discharge gas from the compressor is cooled when the operating state is the cooling operation, and   the discharge gas is not cooled when the operating state is the heating operation.