Heat pump system and control method thereof

Abstract

A heat pump system may include a compressor, a water-refrigerant heat exchanger, an expansion valve, an outdoor heat exchanger, an outlet temperature sensor configured to detect an outlet temperature of the water-refrigerant heat exchanger, an outside temperature sensor, a discharge pressure sensor, a suction pressure sensor, and at least one processor. The at least one processor may obtain, during a heating operation, a first target discharge temperature of the compressor based on an output value from the outlet temperature sensor and an output value from the outside temperature sensor, obtain a second target discharge temperature of the compressor based on an output value from the discharge pressure sensor and an output value from the suction pressure sensor, set any one of the first target discharge temperature or the second target discharge temperature to a final target discharge temperature, and control the expansion valve based on the final target discharge temperature.

1 . A heat pump system comprising:
 a compressor;   a water-refrigerant heat exchanger connected to the compressor;   an expansion valve connected to the water-refrigerant heat exchanger;   an outdoor heat exchanger connected to the expansion valve;   an outlet temperature sensor configured to detect an outlet temperature of the water-refrigerant heat exchanger;   an outside temperature sensor configured to detect an outside temperature;   a discharge pressure sensor configured to detect pressure of a refrigerant discharged from the compressor;   a suction pressure sensor configured to detect pressure of a refrigerant that enters the compressor; and   at least one processor configured to obtain, during a heating operation, a first target discharge temperature of the compressor based on an output value from the outlet temperature sensor and an output value from the outside temperature sensor, obtain a second target discharge temperature of the compressor based on an output value from the discharge pressure sensor and an output value from the suction pressure sensor, to set any one of the first target discharge temperature or the second target discharge temperature to a final target discharge temperature, and to control the expansion valve based on the final target discharge temperature.   
     
     
         2 . The heat pump system of  claim 1 , wherein the at least one processor is further configured to obtain a high-pressure saturation temperature value according to the output value from the outlet temperature sensor, obtain a high-pressure value according to the high-pressure saturation temperature value, obtain a low-pressure saturation temperature value according to the output value from the outside temperature sensor, obtain a low-pressure value according to the low-pressure saturation temperature value, and set discharge temperature corresponding to the high-pressure value and the low-pressure value to the first target discharge temperature. 
     
     
         3 . The heat pump system of  claim 2 , wherein the at least one processor is further configured to:
 set, to the high-pressure saturation temperature value, a value obtained by adding a first value to the output value from the outlet temperature sensor, and   set, to the low-pressure saturation temperature value, a value obtained by subtracting a second value from the output value from the outside temperature sensor.   
     
     
         4 . The heat pump system of  claim 1 , wherein the at least one processor is further configured to set, to the second target discharge temperature, a discharge temperature corresponding to the output value from the discharge pressure sensor and the output value from the suction pressure sensor. 
     
     
         5 . The heat pump system of  claim 1 , wherein the at least one processor is further configured to further correct the second target discharge temperature based on an operation frequency of the compressor. 
     
     
         6 . The heat pump system of  claim 5 , wherein the at least one processor is further configured to correct the second target discharge temperature such that as the operation frequency of the compressor increase, the second target discharge temperature increases. 
     
     
         7 . The heat pump system of  claim 1 , wherein the at least one processor is further configured to further correct the second target discharge temperature based on the outside temperature. 
     
     
         8 . The heat pump system of  claim 7 , wherein the at least one processor is further configured to:
 correct the second target discharge temperature such that as the outside temperature increases, the second target discharge temperature increases; and   correct the second target discharge temperature such that as the outside temperature decreases, the second target discharge temperature decreases.   
     
     
         9 . The heat pump system of  claim 1 , wherein the at least one processor is further configured to set a greater one of the first target discharge temperature and the second target discharge temperature to the final target discharge temperature. 
     
     
         10 . The heat pump system of  claim 1 , wherein the at least one processor is further configured to set, during a first section of the heating operation, the first target discharge temperature to the final target discharge temperature. 
     
     
         11 . The heat pump system of  claim 1 , wherein the at least one processor is further configured to set, during a second section of the heating operation, the second target discharge temperature to the final target discharge temperature. 
     
     
         12 . The heat pump system of  claim 1 , wherein the refrigerant is a R290 refrigerant. 
     
     
         13 . A method of controlling a heat pump system, comprising:
 obtaining, during a heating operation, a first target discharge temperature of a compressor based on outlet temperature of a water-refrigerant heat exchanger and outside temperature;   obtaining a second target discharge temperature of the compressor based on pressure of a refrigerant discharged from the compressor and pressure of a refrigerant that enters the compressor;   setting any one of the first target discharge temperature or the second target discharge temperature to a final target discharge temperature; and   controlling an expansion valve based on the final target discharge temperature.   
     
     
         14 . The method of  claim 13 , wherein the obtaining of the first target discharge temperature comprises:
 setting a high-pressure saturation temperature value according to the outlet temperature;   setting a high-pressure value according to the high-pressure saturation temperature value;   setting a low-pressure saturation temperature value according to the outside temperature;   setting a low-pressure value according to the low-pressure saturation temperature value; and   setting, to the first target discharge temperature, a discharge temperature corresponding to the high-pressure value and the low-pressure value.   
     
     
         15 . The method of  claim 13 , wherein the obtaining of the second target discharge temperature comprises:
 setting, to the second target discharge temperature, a discharge temperature corresponding to the pressure of the refrigerant discharged from the compressor and the pressure of the refrigerant that enters the compressor.   
     
     
         16 . A method of controlling a heat pump system, comprising:
 detecting, during a heating operation, an outlet temperature of water heat-exchanged with a refrigerant in a water-refrigerant heat exchanger;   detecting an outside temperature;   obtaining a first target discharge temperature based on the outlet temperature and the outside temperature;   detecting a temperature of the refrigerant heat-exchanged in the water-refrigerant heat exchanger;   detecting a temperature of a refrigerant heat-exchanged in an outdoor heat exchanger;   obtaining a second target discharge temperature based on the temperature of the refrigerant heat-exchanged in the water-refrigerant heat exchanger and the temperature of the refrigerant heat-exchanged in the outdoor heat exchanger;   setting any one of the first target discharge temperature or the second target discharge temperature to a final target discharge temperature; and   controlling an expansion valve connected to the water-refrigerant heat exchanger based on the final target discharge temperature.   
     
     
         17 . The method of  claim 16 , wherein the outside temperature is detected using an outside temperature sensor positioned adjacent the outdoor heat exchanger. 
     
     
         18 . The method of  claim 16 , wherein:
 the first target discharge temperature is obtained according to a correlation function, which inputs the outlet temperature and the outside temperature; and   the second target discharge temperature is obtained according to an other correlation function, which inputs the temperature of the refrigerant heat-exchanged in the water-refrigerant heat exchanger and the temperature of the refrigerant heat-exchanged in the outdoor heat exchanger.   
     
     
         19 . The method of  claim 18 , wherein:
 the other correlation function receives a first output value from a first temperature sensor positioned around a refrigerant outlet of the water-refrigerant heat exchanger, and a second output value from a second temperature sensor positioned inside the outdoor heat exchanger; and   based on the first output value and the second output value, the other correlation function generates an optimal discharge temperature as the second target discharge temperature.   
     
     
         20 . The method of  claim 16 , wherein setting any one of the first target discharge temperature or the second target discharge temperature to the final target discharge temperature includes setting a greater one of the first target discharge temperature and the second target discharge temperature to the final target discharge temperature.