Refrigeration cycle apparatus and refrigeration cycle control method

Abstract

An integrated air-conditioning and hot-water-supply system includes a compressor, a plate-type water heat exchanger, a hot-water-supply pressure-reducing mechanism, and an outdoor heat exchanger. Moreover, the integrated air-conditioning and hot-water-supply system includes a high-pressure sensor that detects a high pressure in the compressor, and a controller that calculates a condensing temperature of the plate-type water heat exchanger based on the high pressure detected by the high-pressure sensor. When the calculated condensing temperature is higher than or equal to a preset target condensing-temperature value, the controller performs condensing-temperature control for controlling the operating frequency of the compressor based on a difference between the calculated condensing temperature and the target condensing-temperature value, and performs opening-degree control for controlling the opening degree of the hot-water-supply pressure-reducing mechanism concurrently with the condensing-temperature control based on a difference between a current opening degree of the hot-water-supply pressure-reducing mechanism and a preset target opening-degree value.

1 . A refrigeration cycle apparatus comprising:
 a refrigeration cycle mechanism having a compressor whose operating frequency is controllable, a first radiator, a first pressure-reducing mechanism whose opening degree is controllable, and a first evaporator, wherein a refrigerant sequentially circulates through the compressor, the first radiator, the first pressure-reducing mechanism, and the first evaporator;   a high-pressure sensor that detects a high pressure between a discharge side of the compressor and a liquid side of the first pressure-reducing mechanism; and   a controller that controls the operating frequency of the compressor and controlling the opening degree of the first pressure-reducing mechanism based on a degree of subcooling of the first radiator, wherein,   when a condensing temperature of the first radiator that is obtained based on the high pressure detected by the high-pressure sensor is higher than or equal to a preset target condensing-temperature value,   the controller
 (a) performs condensing-temperature control for reducing the operating frequency of the compressor based on a difference between the condensing temperature and the target condensing-temperature value, and 
 (b) performs opening-degree control for increasing the opening degree of the first pressure-reducing mechanism more than opening-degree control under the control based on the degree of the subcooling. 
   
     
     
         2 . The refrigeration cycle apparatus of  claim 1 , wherein
 the first pressure-reducing mechanism performs the opening-degree control based on a preset target opening degree value so as to ensure a predetermined level of a heat-radiation capacity of the first radiator.   
     
     
         3 . The refrigeration cycle apparatus of  claim 2 ,
 wherein the first radiator includes   an inflowing-water-pipe connection section connected to an inflowing water pipe into which water flows,   an outflowing-water-pipe connection section connected to an outflowing water pipe from which the water flows, and   a water pipe through which the water flowing in from the inflowing water pipe passes and flows out to the outflowing water pipe,   wherein the first radiator heats the water passing through the water pipe by radiating heat to the water, and   wherein the target heat-radiation-capacity value of the first radiator is set in correspondence with an upper limit value in design for an inlet water temperature of the water flowing into the water pipe from the inflowing water pipe.   
     
     
         4 . The refrigeration cycle apparatus of  claim 1 , wherein the controller includes a storage unit that stores frequency/opening-degree correspondence information in which the operating frequency of the compressor and a preset the target opening-degree value of the first pressure-reducing mechanism are stored in correspondence with each other, and wherein when the controller concurrently performs the condensing-temperature control and the opening-degree control, the controller refers to the frequency/opening-degree correspondence information so as to identify the target opening-degree value corresponding to a current operating frequency of the compressor from the frequency/opening-degree correspondence information, and uses the identified target opening-degree value as the target opening-degree value in the opening-degree control. 
     
     
         5 . The refrigeration cycle apparatus of  claim 1 ,
 wherein the first evaporator is disposed outdoors,   wherein the refrigeration cycle apparatus comprises an outdoor-air temperature sensor that detects an outdoor-air temperature around the first evaporator, and   wherein the controller includes a storage unit that stores outdoor-air-temperature/opening-degree correspondence information in which the outdoor-air temperature and the preset target opening-degree value of the first pressure-reducing mechanism are stored in correspondence with each other, and wherein when the controller concurrently performs the condensing-temperature control and the opening-degree control, the controller refers to the outdoor-air-temperature/opening-degree correspondence information so as to identify the target opening-degree value corresponding to the outdoor-air temperature detected by the outdoor-air temperature sensor from the outdoor-air-temperature/opening-degree correspondence information, and uses the identified target opening-degree value as the target opening-degree value in the opening-degree control.   
     
     
         6 . The refrigeration cycle apparatus of  claim 1 ,
 wherein the first evaporator is disposed outdoors,   wherein the refrigeration cycle apparatus comprises:   an outdoor-air temperature sensor that detects an outdoor-air temperature around the first evaporator; and   an evaporating temperature sensor that detects an evaporating temperature of the refrigerant in the first evaporator, and   wherein the controller receives data of two or more sets of a temperature difference between the outdoor-air temperature around the first evaporator and the evaporating temperature of the first evaporator and an evaporating capacity of the first evaporator corresponding to the temperature difference, determines a functional relationship between the temperature difference and the evaporating capacity based on the received data, refers to the determined functional relationship so as to identify the evaporating capacity corresponding to the temperature difference between the outdoor-air temperature detected by the outdoor-air temperature sensor and the evaporating temperature detected by the evaporating temperature sensor from the functional relationship, calculates a compressor input, which indicates compressing work done on the refrigerant by the compressor, from the operating frequency of the compressor, the condensing temperature, and the evaporating temperature detected by the evaporating temperature sensor, calculates a heat-radiation capacity of the first radiator from the identified evaporating capacity and the calculated compressor input, determines the target opening-degree value of the first pressure-reducing mechanism in accordance with a difference between the calculated heat-radiation capacity and a preliminarily-stored target heat-radiation-capacity value, and uses the determined target opening-degree value as the target opening-degree value in the opening-degree control.   
     
     
         7 . The refrigeration cycle apparatus of  claim 1 , comprising:
 a branch flow path branching from the discharge side of the compressor and having a second radiator and a second pressure-reducing mechanism, the branch flow path being connected to the second radiator and the second pressure-reducing mechanism sequentially from the discharge side of the compressor and merging with an intermediate section between the first pressure-reducing mechanism and the first evaporator,   wherein the controller performs a concurrent heat-radiation operation in which the refrigerant discharged from the compressor is circulated by being made to flow into the first radiator and the second radiator, and wherein when the condensing temperature becomes higher than or equal to the target condensing-temperature value during the concurrent heat-radiation operation, the controller performs a switching process for alternately switching between a process for making the discharged refrigerant flow into the first radiator and a process for making the discharged refrigerant flow into the second radiator.   
     
     
         8 . The refrigeration cycle apparatus of  claim 7 ,
 wherein the second radiator exchanges heat with indoor air,   wherein the refrigeration cycle apparatus comprises an indoor temperature sensor that detects an indoor temperature, and   wherein the controller performs the switching process based on a temperature difference obtained by subtracting a preliminarily-stored preset indoor temperate from the indoor temperature detected by the indoor temperature sensor.   
     
     
         9 . The refrigeration cycle apparatus of  claim 8 , wherein
 when the discharged refrigerant is made to flow only into the second radiator due to the switching process, the controller controls the operating frequency of the compressor and the opening degree of the first pressure-reducing mechanism so that the temperature difference is greater than a predetermined positive value, and wherein when the temperature difference becomes greater than the predetermined positive value, the controller performs the switching process so as to make the discharged refrigerant flow only into the first radiator.   
     
     
         10 . The refrigeration cycle apparatus of  claim 1 , comprising:
 a heat-absorption branch flow path that branches from a branch section between the first pressure-reducing mechanism and the first evaporator and merges with a suction side of the compressor, the heat-absorption branch flow path having a second evaporator and a pressure-reducing mechanism for the second evaporator, the heat-absorption branch flow path being connected to the pressure-reducing mechanism for the second evaporator and to the second evaporator sequentially from the branch section and merging with the suction side of the compressor,   wherein the controller performs a concurrent heat-absorption and heat-radiation operation in which a heat-radiation operation of the first radiator and a heat-absorption operation of the second evaporator are concurrently performed, the heat-radiation operation being operation in which the refrigerant discharged from the compressor is suctioned into the compressor from the suction side thereof via the first radiator, the first pressure-reducing mechanism, the branch section, and the first evaporator, the heat-absorption operation being operation in which the discharged refrigerant is suctioned into the compressor from the suction side thereof via the first radiator, the first pressure-reducing mechanism, the branch section, the pressure-reducing mechanism for the second evaporator, and the second evaporator, and wherein when the condensing temperature becomes higher than or equal to the target condensing-temperature value during the concurrent heat-reception and heat-radiation operation, the controller performs a switching process for alternately switching between the heat-radiation operation and the heat-absorption operation.   
     
     
         11 . The refrigeration cycle apparatus of  claim 10 ,
 wherein the second evaporator exchanges heat with indoor air,   wherein the refrigeration cycle apparatus comprises an indoor temperature sensor that detects an indoor temperature, and   wherein the controller performs the switching process based on a temperature difference obtained by subtracting a preliminarily-stored preset indoor temperature from the indoor temperature detected by the indoor temperature sensor.   
     
     
         12 . The refrigeration cycle apparatus of  claim 11 , wherein when only the heat-absorption operation is performed due to the switching process, the controller controls the operating frequency of the compressor and the opening degree of the first pressure-reducing mechanism so that the temperature difference is smaller than a predetermined negative value, and wherein when the temperature difference becomes smaller than the predetermined negative value, the controller performs the switching process so that only the heat-radiation operation is performed. 
     
     
         13 . The refrigeration cycle apparatus of  claim 1 ,
 wherein the refrigeration cycle apparatus uses a refrigerant that operates at a critical pressure or higher, and   wherein when the high pressure detected by the high-pressure sensor is higher than or equal to a preset target high-pressure value, the controller performs high-pressure control for controlling the operating frequency of the compressor based on a difference between the high pressure and the target high-pressure value, and performs opening-degree control for controlling the opening degree of the first pressure-reducing mechanism concurrently with the high-pressure control based on the difference between the current opening degree of the first pressure-reducing mechanism and the preset target opening-degree value.   
     
     
         14 . A refrigeration cycle control method for performing an operation on a refrigeration cycle apparatus, the refrigeration cycle apparatus including a refrigeration cycle mechanism having a compressor whose operating frequency is controllable, a first radiator, a first pressure-reducing mechanism whose opening degree is controllable, and a first evaporator, wherein a refrigerant sequentially circulates through the compressor, the first radiator, the first pressure-reducing mechanism, and the first evaporator; and a high-pressure sensor that detects a high pressure between a discharge side of the compressor and a liquid side of the first pressure-reducing mechanism, the refrigeration cycle apparatus controlling the operating frequency of the compressor and controlling the opening degree of the first pressure-reducing mechanism based on a degree of subcooling of the first radiator, the method comprising:
 when a condensing temperature of the first radiator corresponding to the high pressure detected by the high-pressure sensor is higher than or equal to a preset target condensing-temperature value,   performing condensing-temperature control for reducing the operating frequency of the compressor based on a difference between the condensing temperature and the preset target condensing-temperature value, and   performing opening-degree control for increasing the opening degree of the first pressure-reducing mechanism more than opening-degree control under the control based the degree of on the subcooling.