Air-conditioning apparatus

Abstract

An air-conditioning apparatus includes a refrigerant circuit in which an outdoor unit, at least one load-side expansion device, and at least one load-side heat exchanger are connected by pipes to allow refrigerant to circulate. The outdoor unit includes a compressor including an injection port allowing the refrigerant to flow into a suction chamber, a heat-source-side heat exchanger for heat exchange for the refrigerant, and an accumulator. The load-side heat exchanger transfers heat between a load and the refrigerant. The outdoor unit includes: an injection pipe having one end connected between the heat-source-side heat exchanger and the load-side expansion device, and the other end connected to the injection port, in the refrigerant circuit; an outdoor-side expansion device located downstream from the one end of the injection pipe in the flow of the refrigerant from the load-side expansion device to the heat-source-side heat exchanger; and an injection expansion device that adjusts the amount of the refrigerant flowing through the injection pipe. Also, a controller is provided to control the opening degrees of the outdoor-side expansion device and the injection expansion device.

1 . An air-conditioning apparatus comprising:
 an outdoor unit including a compressor, a heat-source-side heat exchanger, and an accumulator, the compressor including a suction chamber having an injection port that allows refrigerant to flow into the suction chamber, the compressor being configured to compress and discharge the refrigerant, the heat-source-side heat exchanger being configured to cause heat exchange for the refrigerant to be performed, the accumulator being configured to accumulate the refrigerant;   at least one load-side expansion device configured to reduce a pressure of the refrigerant; and   at least one load-side heat exchanger configured to cause heat exchange to be performed between a load and the refrigerant,   the outdoor unit, the at least one load-side expansion device, and the at least one load-side heat exchanger being connected by pipes, whereby a refrigerant circuit is formed to circulate the refrigerant,   the outdoor unit including:
 an injection pipe having one end connected between the heat-source-side heat exchanger and the load-side expansion device and an other end connected to the injection port, the injection pipe being configured to allow part of the refrigerant in the refrigerant circuit to flow toward the injection port; 
 an outdoor-side expansion device located downstream of the one end of the injection pipe in a flow of the refrigerant in a case where the refrigerant flows from the load-side expansion device to the heat-source-side heat exchanger in the refrigerant circuit, the outdoor-side expansion device being configured to reduce the pressure of the refrigerant to adjust a flow rate thereof; and 
 an injection expansion device configured to adjust an amount of the refrigerant that flows in the injection pipe, 
   the air-conditioning apparatus further comprising a controller configured to control an opening degree of the outdoor-side expansion device and an opening degree of the injection expansion device.   
     
     
         2 . The air-conditioning apparatus of  claim 1 , wherein
 a plurality of the outdoor units are connected in parallel by pipes, whereby the refrigerant circuit is formed.   
     
     
         3 . The air-conditioning apparatus of  claim 1 , wherein when determining that a discharge temperature of the refrigerant that is discharged from the compressor is higher than or equal to a predetermined discharge temperature threshold, the controller controls the opening degree of the injection expansion device such that the discharge temperature becomes lower than the discharge temperature threshold. 
     
     
         4 . The air-conditioning apparatus of  claim 1 , wherein the controller controls the opening degree of the injection expansion device such that a discharge temperature of the refrigerant that is discharged from the compressor approaches a predetermined discharge temperature threshold. 
     
     
         5 . The air-conditioning apparatus of  claim 1 , wherein when determining a discharge temperature of the compressor that is reduced because of a return liquid from the accumulator is lower than or equal to a predetermined liquid-level adjustment threshold, the controller controls the opening degree of the outdoor-side expansion device such that the discharge temperature of the compressor becomes higher than the liquid-level adjustment threshold. 
     
     
         6 . The air-conditioning apparatus of  claim 5 , wherein the liquid-level adjustment threshold is a value obtained by adding a temperature value by which the discharge temperature is reduced in accordance with the opening degree of the injection expansion device, to the discharge temperature that is reduced because of the return liquid from the accumulator, when the injection expansion device is in an opened state. 
     
     
         7 . The air-conditioning apparatus of  claim 3 , wherein the controller calculates a degree of discharge superheat of the refrigerant that is discharged from the compressor, and performs processing based on the degree of discharge superheat instead of the discharge temperature. 
     
     
         8 . The air-conditioning apparatus of  claim 1 , wherein
 the outdoor unit further includes a refrigerant flow switching device configured to switch a flow passage for the refrigerant between a flow passage for a cooling operation mode and a flow passage for a heating operation mode, and   the controller controls the opening degree of the injection expansion device in the heating operation mode.   
     
     
         9 . The air-conditioning apparatus of  claim 8 , wherein the heating operation mode includes a heating only operation mode in which ones of the load-side heat exchangers that are not in a stopped state all operate as condensers, and a heating main operation mode in which one or ones of the load-side heat exchangers not being in the stopped state operate as condensers, and a remaining one or ones of the load-side heat exchangers not being in the stopped state operate as evaporators. 
     
     
         10 . The air-conditioning apparatus of  claim 1 , further comprising:
 a plurality of indoor units each including the load-side expansion device and the load-side heat exchanger; and   a relay unit configured to operate as a relay between the outdoor unit and the plurality of indoor units,   wherein the outdoor unit, the plurality of indoor units, and the relay unit are connected by pipes such that the refrigerant circulates between components included in the outdoor unit and components included in the plurality of indoor units, through the relay unit, whereby the refrigerant circuit is formed.   
     
     
         11 . The air-conditioning apparatus of  claim 1 , comprising:
 the refrigerant circuit including the load-side heat exchanger, the load-side heat exchanger being configured to cause heat exchange to be performed between the refrigerant and a heat medium that is applied as the load and different from the refrigerant; and   a heat-medium circulation circuit in which a pump, the load-side heat exchanger, a use-side heat exchanger, and a heat-medium flow adjusting device are connected by pipes to circulate the heat medium, the pump being configured to pressurize the heat medium, the use-side heat exchanger being configured to cause heat exchange for air to be conditioned to be performed, the heat-medium flow adjusting device being configured to adjust a flow rate of the heat medium that flows into and out of the use-side heat exchanger.   
     
     
         12 . The air-conditioning apparatus of  claim 1 , wherein the heat-source-side heat exchanger is a water-refrigerant heat exchanger configured to cause heat exchange to be performed between water and the refrigerant.