Refrigeration cycle apparatus

Abstract

A refrigeration cycle apparatus includes a compressor, a first heat exchanger, an expansion valve in which refrigerant flows from the first heat exchanger, a second heat exchanger having a plurality of heat transfer tubes and a header, a first refrigerant pipe connecting the expansion valve with a refrigerant inlet of the header, a second refrigerant pipe connecting the second heat exchanger with a refrigerant suction inlet of the compressor, a bypass circuit having a bypass inlet connected to the header at a position different from that of the refrigerant inlet of the header and a bypass outlet connected to the second refrigerant pipe, a bypass valve configured to make a pressure of the refrigerant in the bypass circuit lower than a pressure of the refrigerant in the header, and a refrigerant circuit auxiliary unit configured to deliver gas-phase refrigerant from the bypass circuit to the bypass outlet.

1 . A refrigeration cycle apparatus comprising:
 a compressor configured to compress and discharge refrigerant;   a first heat exchanger into which the refrigerant discharged from the compressor flows;   an expansion valve configured to expand the refrigerant flowing from the first heat exchanger;   a second heat exchanger having a plurality of heat transfer tubes and a header configured to distribute, to the plurality of heat transfer tubes, the refrigerant flowing from the expansion valve;   a first refrigerant pipe connecting the expansion valve with a refrigerant inlet of the header;   a second refrigerant pipe connecting the second heat exchanger with a refrigerant inlet of the compressor;   a bypass circuit having
 a bypass inlet connected to the header at a position different from that of the refrigerant inlet of the header and 
 a bypass outlet connected to the second refrigerant pipe; 
   a bypass valve provided in the bypass circuit and configured to make a pressure of the refrigerant in the bypass circuit lower than a pressure of the refrigerant in the header; and   a refrigerant circuit auxiliary unit configured to deliver gas-phase refrigerant from the bypass circuit to the bypass outlet.   
     
     
         2 . The refrigeration cycle apparatus of  claim 1 , wherein the refrigerant circuit auxiliary unit is a secondary heat exchanger provided between the bypass valve and the bypass outlet in the bypass circuit and configured to heat the refrigerant flowing out from the bypass valve. 
     
     
         3 . The refrigeration cycle apparatus of  claim 2 , further comprising a control substrate configured to control equipment including the compressor,
 wherein the refrigerant circuit auxiliary unit is configured to be in contact with the control substrate.   
     
     
         4 . The refrigeration cycle apparatus of  claim 2 , wherein the refrigerant circuit auxiliary unit is integrated with the second heat exchanger. 
     
     
         5 . The refrigeration cycle apparatus of  claim 4 , further comprising a fan configured to send air to the second heat exchanger and the secondary heat exchanger,
 wherein the refrigerant circuit auxiliary unit is disposed at such a position that a speed of air sent by the fan to the refrigerant circuit auxiliary unit is lower than a speed of air sent by the fan to the second heat exchanger.   
     
     
         6 . The refrigeration cycle apparatus of  claim 4 , wherein the refrigerant circuit auxiliary unit is configured such that the refrigerant circuit auxiliary unit is smaller in heat transfer area than the second heat exchanger. 
     
     
         7 . The refrigeration cycle apparatus of  claim 2 , wherein the refrigerant circuit auxiliary unit is configured such that the refrigerant circuit auxiliary unit is smaller in amount of heat exchange than the second heat exchanger. 
     
     
         8 . The refrigeration cycle apparatus  claim 2 , wherein the bypass valve is configured such that the bypass valve is smaller in pressure loss than the second heat exchanger in a case in which an opening degree of the bypass valve is fully open. 
     
     
         9 . The refrigeration cycle apparatus of  claim 2 , wherein
 the plurality of heat transfer tubes are placed at different heights in the second heat exchanger in a direction of gravitational force,   the refrigeration cycle apparatus further comprising:   a temperature sensor provided on one of the plurality of heat transfer tubes that is above an intermediate position of the heights in the second heat exchanger and configured to detect a temperature of refrigerant flowing through the heat transfer tube; and   a controller configured to control an opening degree of the bypass valve based on a detected value of the temperature sensor,   wherein the controller is configured to increase the opening degree of the bypass valve in a case in which the detected value is higher than a predetermined threshold and decrease the opening degree of the bypass valve in a case in which the detected value is lower than the threshold.   
     
     
         10 . The refrigeration cycle apparatus of  claim 1 , further comprising a liquid pipe connecting a refrigerant return port provided in the first refrigerant pipe with the refrigerant circuit auxiliary unit,
 wherein   the refrigerant circuit auxiliary unit is a gas-liquid separator provided between the header and the bypass valve in the bypass circuit and configured to separate the refrigerant flowing from the header into gas-phase refrigerant and liquid-phase refrigerant, and   the refrigerant circuit auxiliary unit is configured to cause the gas-phase refrigerant to flow out to the bypass valve via the bypass circuit and cause the liquid-phase refrigerant to flow out to the refrigerant return port via the liquid pipe.   
     
     
         11 . The refrigeration cycle apparatus of  claim 1 , wherein
 the refrigerant circuit auxiliary unit is a gas-liquid separator provided in the first refrigerant pipe and configured to separate refrigerant flowing from the expansion valve into the header into gas-phase refrigerant and liquid-phase refrigerant, and   the bypass circuit is disposed to pass through the refrigerant circuit auxiliary unit to cause the refrigerant flowing out from the bypass valve to exchange heat with the liquid-phase refrigerant stored in the refrigerant circuit auxiliary unit.   
     
     
         12 . The refrigeration cycle apparatus of  claim 1 , wherein the bypass valve is a mechanical differential pressure regulating valve configured to keep a pressure difference of the refrigerant between a refrigerant flow inlet and a refrigerant flow outlet of the bypass valve within a certain range. 
     
     
         13 . The refrigeration cycle apparatus of  claim 1 , wherein the bypass outlet is connected to the second refrigerant pipe at a position closer to the compressor than an intermediate position between a refrigerant outlet of the second heat exchanger and the refrigerant suction inlet of the compressor. 
     
     
         14 . The refrigeration cycle apparatus of  claim 1 , further comprising a controller configured to control an operating frequency of the compressor and an opening degree of the bypass valve,
 wherein   in making the operating frequency of the compressor lower than a present frequency, the controller is configured to make the opening degree of the bypass valve larger than a present opening degree before changing the operating frequency, and   in making the operating frequency of the compressor higher than the present frequency, the controller makes the opening degree of the bypass valve smaller than the present opening degree before changing the operating frequency.   
     
     
         15 . The refrigeration cycle apparatus of  claim 1 , wherein
 the header is configured to linearly extend in parallel to a direction of gravitational force, and   the bypass inlet is connected to the header at a position away from the refrigerant inlet in a direction opposite to the direction of gravitational force.   
     
     
         16 . The refrigeration cycle apparatus of  claim 1 , wherein
 the header is configured to linearly extend in parallel to a plane orthogonal to a direction of gravitational force, and   the bypass inlet is connected to the header downstream of the refrigerant inlet in a direction in which the refrigerant flows through the header.