Liquid circulation heating system and method of controlling the same

Abstract

A liquid circulation heating system includes a heat pump for producing a heated liquid and a heating radiator. The heat pump has a heat pump circuit in which a compressor, a radiator, a decompressor, and an evaporator are connected in series. The heat pump circuit is charged with a zeotropic refrigerant mixture of at least two refrigerants having different boiling points. The system is configured so that the composition ratio of a higher boiling point refrigerant in the refrigerant circulating through the heat pump circuit increases when the liquid supplied to the radiator has a relatively high temperature.

1 . A liquid circulation heating system for performing air-heating by heating a liquid to produce a heated liquid and releasing heat of the heated liquid from a heating radiator, the system comprising a heat pump circuit for circulating a refrigerant,
 wherein the heat pump circuit includes a refrigerant radiator for heating the liquid by radiating heat from the refrigerant to produce the heated liquid,   the heat pump circuit is charged with a zeotropic refrigerant mixture of at least two refrigerants having different boiling points, as the refrigerant, and   the liquid circulation heating system is configured so that a composition ratio of a higher boiling point refrigerant in the refrigerant circulating through the heat pump circuit increases when the liquid supplied to the refrigerant radiator has a relatively high temperature.   
   
   
       2 . The liquid circulation heating system according to  claim 1 , wherein
 the heat pump circuit further includes: a compressor for compressing the refrigerant; a decompressor for decompressing the refrigerant; an evaporator for evaporating the refrigerant; and a vapor-liquid separator for separating the refrigerant into a gas refrigerant and a liquid refrigerant, and   the liquid circulation heating system further comprises a controller for performing a control operation to reduce an amount of the liquid refrigerant in the vapor-liquid separator when the liquid supplied to the refrigerant radiator has a relatively high temperature.   
   
   
       3 . The liquid circulation heating system according to  claim 2 , wherein the vapor-liquid separator is an accumulator provided between the evaporator and the compressor. 
   
   
       4 . The liquid circulation heating system according to  claim 3 , wherein
 the decompressor is an expansion valve, and   the controller reduces an opening of the expansion valve when the liquid supplied to the refrigerant radiator has a relatively high temperature.   
   
   
       5 . The liquid circulation heating system according to  claim 3 , wherein
 the heat pump circuit further includes, between the evaporator and the accumulator, a heater for heating the refrigerant to be fed to the accumulator from the evaporator, and   the controller increases an amount of the heating applied to the refrigerant by the heater when the liquid supplied to the refrigerant radiator has a relatively high temperature.   
   
   
       6 . The liquid circulation heating system according to  claim 5 , wherein
 the heat pump circuit further includes a bypass passage that bypasses the decompressor, and   the heater is a heat exchanger for exchanging heat between the refrigerant flowing through the bypass passage and the refrigerant to be fed to the accumulator from the evaporator.   
   
   
       7 . The liquid circulation heating system according to  claim 2 , wherein
 the decompressor includes: a first expansion valve for decompressing the refrigerant after the refrigerant radiates heat in the refrigerant radiator; and a second expansion valve for further decompressing the refrigerant after the refrigerant is decompressed by the first expansion valve,   the vapor-liquid separator is a receiver provided between the first expansion valve and the second expansion valve, and   the controller reduces an opening of the first expansion valve and increases an opening of the second expansion valve when the liquid supplied to the refrigerant radiator has a relatively high temperature.   
   
   
       8 . The liquid circulation heating system according to  claim 1 , further comprising:
 a supply pipe for guiding the liquid from the heating radiator to the refrigerant radiator; and   a recovery pipe for guiding the heated liquid from the refrigerant radiator to the heating radiator.   
   
   
       9 . The liquid circulation heating system according to  claim 1 , further comprising:
 a tank for storing the produced heated liquid;   a supply pipe for guiding the liquid from a lower portion of the tank to the refrigerant radiator;   a recovery pipe for guiding the heated liquid from the refrigerant radiator to an upper portion of the tank;   a feed pipe for feeding the heated liquid stored in the tank to the heating radiator; and   a return pipe for returning the heated liquid to the tank after the heated liquid radiates heat in the heating radiator.   
   
   
       10 . The liquid circulation heating system according to  claim 1 , further comprising:
 a tank for storing the produced heated liquid;   a supply pipe for guiding the liquid from a lower portion of the tank to the refrigerant radiator;   a recovery pipe for guiding the heated liquid from the refrigerant radiator to an upper portion of the tank;   a heat exchanger, disposed in the tank, for exchanging heat between the heated liquid stored in the tank and a heat transfer liquid;   a feed pipe for feeding the heat transfer liquid to the heating radiator after the heat transfer liquid is heated in the heat exchanger; and   a return pipe for returning the heat transfer liquid to the heat exchanger after the heat transfer liquid radiates heat in the heating radiator.   
   
   
       11 . The liquid circulation heating system according to  claim 1 , wherein the liquid is water, and the heated liquid is hot water. 
   
   
       12 . A method of controlling a liquid circulation heating system for performing air-heating by heating a liquid to produce a heated liquid and releasing heat of the heated liquid from a heating radiator,
 wherein the liquid circulation heating system includes a heat pump circuit for circulating a refrigerant, and the heat pump circuit includes: a refrigerant radiator for heating the liquid by radiating heat from the refrigerant to produce the heated liquid; a compressor for compressing the refrigerant; a decompressor for decompressing the refrigerant; an evaporator for evaporating the refrigerant; and a vapor-liquid separator for separating the refrigerant into a gas refrigerant and a liquid refrigerant,   the heat pump circuit is charged with a zeotropic refrigerant mixture of at least two refrigerants having different boiling points, as the refrigerant, and   the method comprises the step of controlling an operation of the decompressor to reduce an amount of the liquid refrigerant in the vapor-liquid separator when the liquid supplied to the refrigerant radiator has a relatively high temperature.