Refrigeration System

Abstract

A refrigeration system includes an internal heat exchanger ( 23 ) capable of controlling the temperature of refrigerant flowing towards an expander ( 12 ). Upon change of the operating conditions, the internal heat exchanger ( 23 ) controls the temperature of the refrigerant to control the specific volume or the flow rate of the refrigerant, thereby eliminating imbalance between the flow rate through a compressor ( 11 ) and the flow rate through the expander ( 12 ). In a cooling operation in which the refrigerant circulation amount is larger than in a heating operation, the cooling capacity of the internal heat exchanger ( 23 ) is enhanced as compared to that in the heating operation, thereby increasing the flow rate of refrigerant into the expander ( 12 ) without part of the refrigerant bypassing the expander ( 12 ). This prevents the COP of the refrigeration system from being deteriorated.

1 . A refrigeration system including a refrigerant circuit ( 10 ) in which a compressor ( 11 ), a heat-source side heat exchanger ( 21 ), an expansion mechanism ( 12 ) and a utilization side heat exchanger ( 22 ) are connected to provide a vapor compression refrigeration cycle, the expansion mechanism ( 12 ) being constituted by an expander ( 12 ) for generating power by the expansion of refrigerant, the expander ( 12 ) being mechanically connected to the compressor ( 11 ), the refrigeration system further comprising 
 a temperature controller ( 23 ) capable of controlling the temperature of refrigerant flowing towards the expander ( 12 ).    
   
   
       2 . The refrigeration system of  claim 1 , wherein 
 the refrigerant circuit ( 10 ) is configured to be capable of a heating operation in which refrigerant flowing through the utilization side heat exchanger ( 22 ) releases heat and a cooling operation in which refrigerant flowing through the utilization side heat exchanger ( 22 ) takes heat, and    the temperature controller ( 23 ) is configured to have a higher capacity to cool refrigerant flowing towards the expander ( 12 ) during the cooling operation than during the heating operation.    
   
   
       3 . The refrigeration system of  claim 2 , wherein the temperature controller ( 23 ) is constituted by an internal heat exchanger ( 23 ) in which, during the cooling operation, refrigerant after passing through the heat-source side heat exchanger ( 21 ) serving as a gas cooler is cooled by heat exchange with refrigerant before or after passing through the utilization side heat exchanger ( 22 ) serving as an evaporator.  
   
   
       4 . The refrigeration system of  claim 3 , wherein the internal heat exchanger ( 23 ) is configured so that, during the cooling operation, a refrigerant channel ( 25 ) thereof through which refrigerant before or after passing through the utilization side heat exchanger ( 22 ) serving as an evaporator flows has a higher heat transfer capacity than a refrigerant channel ( 24 ) thereof through which refrigerant after passing through the heat-source side heat exchanger ( 21 ) serving as a gas cooler flows and that, during the heating operation, the refrigerant channel ( 24 ) through which refrigerant before or after passing through the heat-source side heat exchanger ( 21 ) serving as an evaporator flows has a lower heat transfer capacity than the refrigerant channel ( 25 ) through which refrigerant after passing through the utilization side heat exchanger ( 22 ) serving as a gas cooler flows.  
   
   
       5 . The refrigeration system of  claim 4 , wherein the internal heat exchanger ( 23 ) includes a heat transfer fin ( 26 ) provided on the refrigerant channel ( 25 ) through which, during the cooling operation, refrigerant before or after passing through the utilization side heat exchanger ( 22 ) serving as an evaporator flows and, during the heating operation, refrigerant after passing through the utilization side heat exchanger ( 22 ) serving as a gas cooler flows.  
   
   
       6 . The refrigeration system of  claim 3 , wherein the internal heat exchanger ( 23 ) is configured so that, during the cooling operation, refrigerant before or after passing through the utilization side heat exchanger ( 22 ) serving as an evaporator and refrigerant after passing through the heat-source side heat exchanger ( 21 ) serving as a gas cooler flow therethrough in opposite directions to each other and that, during the heating operation, refrigerant before or after passing through the heat-source side heat exchanger ( 21 ) serving as an evaporator and refrigerant after passing through the utilization side heat exchanger ( 22 ) serving as a gas cooler flow therethrough in the same direction.  
   
   
       7 . The refrigeration system of  claim 3 , wherein the internal heat exchanger ( 23 ) is constituted by a double-pipe heat exchanger including an inner channel ( 24 ) and an outer channel ( 25 ) disposed adjacent each other.  
   
   
       8 . The refrigeration system of  claim 3 , wherein the internal heat exchanger ( 23 ) is constituted by a three-layered plate heat exchanger including an inner channel ( 24 ), a first outer channel ( 25 A) disposed adjacent an outside of the inner channel ( 24 ) and a second outer channel ( 25 B) disposed adjacent another outside of the inner channel ( 24 ).  
   
   
       9 . A refrigeration system including a refrigerant circuit ( 10 ) in which a compressor ( 11 ), a heat-source side heat exchanger ( 21 ), an expansion mechanism ( 12 ) and a utilization side heat exchanger ( 22 ) are connected to provide a vapor compression refrigeration cycle, the refrigerant circuit ( 10 ) being configured to be capable of a heating operation in which refrigerant flowing through the utilization side heat exchanger ( 22 ) releases heat and a cooling operation in which refrigerant flowing through the utilization side heat exchanger ( 22 ) takes heat, the expansion mechanism ( 12 ) being constituted by an expander ( 12 ) for generating power by the expansion of refrigerant, the expander ( 12 ) being mechanically connected to the compressor ( 11 ), the refrigeration system further comprising 
 a temperature controller ( 23 ) capable of controlling the temperature of high-pressure refrigerant flowing towards the expander ( 12 ),    the temperature controller ( 23 ) being configured to cool the high-pressure refrigerant only during the cooling operation but stop the cooling of the high-pressure refrigerant during the heating operation.    
   
   
       10 . The refrigeration system of  claim 9 , wherein the temperature controller ( 23 ) is constituted by an internal heat exchanger ( 23 ) in which during the cooling operation the high-pressure refrigerant is cooled by heat exchange with low-pressure refrigerant.  
   
   
       11 . The refrigeration system of  claim 10 , wherein 
 the internal heat exchanger ( 23 ) includes a first channel ( 27 ) and a second channel ( 28 ) and is configured to be capable of heat exchange between refrigerant flowing through the first channel ( 27 ) and refrigerant flowing through the second channel ( 28 ), and    the internal heat exchanger ( 23 ) is configured so that, during the cooling operation, high-pressure refrigerant flows through the first channel ( 27 ) and low-pressure refrigerant flows through the second channel ( 28 ) and that, during the heating operation, high-pressure refrigerant flows through both the channels ( 27 ,  28 ).    
   
   
       12 . The refrigeration system of  claim 10 , wherein 
 the internal heat exchanger ( 23 ) includes a first channel ( 27 ) and a second channel ( 28 ) and is configured to be capable of heat exchange between refrigerant flowing through the first channel ( 27 ) and refrigerant flowing through the second channel ( 28 ),    the internal heat exchanger ( 23 ) is configured so that, during the cooling operation, high-pressure refrigerant flows through the first channel ( 27 ) and low-pressure refrigerant flows through the second channel ( 28 ), and    the refrigeration system further comprises a bypass passage ( 45 ) that, during the heating operation, allows high-pressure refrigerant to bypass the internal heat exchanger ( 23 ).    
   
   
       13 . The refrigeration system of  claim 10 , wherein 
 the internal heat exchanger ( 23 ) includes a first channel ( 27 ) and a second channel ( 28 ) and is configured to be capable of heat exchange between refrigerant flowing through the first channel ( 27 ) and refrigerant flowing through the second channel ( 28 ),    the internal heat exchanger ( 23 ) is configured so that, during the cooling operation, high-pressure refrigerant flows through the first channel ( 27 ) and low-pressure refrigerant flows through the second channel ( 28 ), and    the refrigeration system further comprises a bypass passage ( 46 ) that, during the heating operation, allows low-pressure refrigerant to bypass the internal heat exchanger ( 23 ).    
   
   
       14 . The refrigeration system of  claim 10 , wherein the internal heat exchanger ( 23 ) is configured so that, during the cooling operation, high-pressure refrigerant after passing through the heat-source side heat exchanger ( 21 ) is cooled therein by heat exchange with low-pressure refrigerant before passing through the utilization side heat exchanger ( 22 ).  
   
   
       15 . The refrigeration system of  claim 10 , wherein the internal heat exchanger ( 23 ) is configured so that, during the cooling operation, high-pressure refrigerant after passing through the heat-source side heat exchanger ( 21 ) is cooled therein by heat exchange with low-pressure refrigerant after passing through the utilization side heat exchanger ( 22 ).  
   
   
       16 . The refrigeration system of  claim 10 , wherein the internal heat exchanger ( 23 ) is configured so that, during the cooling operation, high-pressure refrigerant and low-pressure refrigerant flow therethrough in opposite directions to each other.  
   
   
       17 . The refrigeration system of  claim 9 , wherein refrigerant in the refrigerant circuit ( 10 ) is carbon dioxide.  
   
   
       18 . A refrigeration system including a refrigerant circuit ( 10 ) in which a compressor ( 11 ), a heat-source side heat exchanger ( 21 ), an expander ( 12 ) and a utilization side heat exchanger ( 22 ) are connected to provide a refrigeration cycle, the compressor ( 11 ) being mechanically connected to the expander ( 12 ) to recover expansion power from the expander ( 12 ), the refrigeration system further comprising 
 a gas-liquid separator ( 51 ) for separating refrigerant expanded by the expander ( 12 ) into a liquid refrigerant and a gas refrigerant and temporarily storing the liquid and gas refrigerants,    the gas-liquid separator ( 51 ) comprising an internal heat exchange part ( 50 ) for exchanging heat between the liquid refrigerant separated in the gas-liquid separator ( 51 ) and refrigerant to be introduced into the expander ( 12 ).    
   
   
       19 . The refrigeration system of  claim 18 , further comprising a heat exchange control mechanism ( 60 ) for changing the amount of heat exchange of refrigerant in the internal heat exchange part ( 50 ) according to the operating conditions.  
   
   
       20 . The refrigeration system of  claim 19 , wherein 
 the gas-liquid separator ( 51 ) further comprises a liquid storage section ( 52 ) for storing the separated liquid refrigerant and a heat transfer tube ( 50 ) which is disposed adjacent the liquid storage section ( 52 ) and through which the refrigerant to be introduced into the expander ( 12 ) flows, and    the heat transfer tube ( 50 ) constitutes an internal heat exchange part for exchanging heat between the liquid refrigerant in the liquid storage section ( 52 ) and the refrigerant in the heat transfer tube ( 50 ).    
   
   
       21 . The refrigeration system of  claim 20 , further comprising 
 a refrigerant switching mechanism ( 31 ,  33 ) for switching the circulation direction of refrigerant in the refrigerant circuit ( 10 ) to selectively provide either the cooling operation or the heating operation,    wherein the heat exchange control mechanism ( 60 ) allows heat exchange of refrigerant in the internal heat exchange part ( 50 ) only during the cooling operation.    
   
   
       22 . The refrigeration system of  claim 21 , wherein the heat exchange control mechanism ( 60 ) is constituted by a bypass pipe ( 57 ) allowing refrigerant to bypass the heat transfer tube ( 50 ) and then flow into the expander ( 12 ), a first motor-operated valve ( 36 ) for controlling the flow rate of refrigerant flowing through the heat transfer tube ( 50 ), and a second motor-operated valve ( 37 ) for controlling the flow rate of refrigerant through the bypass pipe ( 57 ).  
   
   
       23 . The refrigeration system of  claim 21 , wherein the heat exchange control mechanism ( 60 ) is constituted by a four-way selector valve ( 32 ).  
   
   
       24 . The refrigeration system of  claim 21 , wherein the heat exchange control mechanism ( 60 ) is constituted by a bypass pipe ( 57 ) allowing refrigerant to bypass the heat transfer tube ( 50 ) and then flow into the expander ( 12 ), a first solenoid shut-off valve ( 34 ) selectively allowing or inhibiting the flow of refrigerant through the heat transfer tube ( 50 ), and a second solenoid shut-off valve ( 35 ) selectively allowing or inhibiting the flow of refrigerant through the bypass pipe ( 57 ).  
   
   
       25 . The refrigeration system of  claim 21 , wherein the heat exchange control mechanism ( 60 ) is constituted by a combination of pipes and check valves ( 81 ,  82 ,  83 ,  84 ).  
   
   
       26 . The refrigeration system of  claim 18 , wherein the refrigerant circuit ( 10 ) further includes a first injection pipe ( 55 ) for sending the gas refrigerant in the gas-liquid separator ( 51 ) to the suction side of the compressor ( 11 ) and a gas control valve ( 38 ) for controlling the flow rate of refrigerant through the first injection pipe ( 55 ).  
   
   
       27 . The refrigeration system of  claim 18 , wherein the refrigerant circuit ( 10 ) further includes a second injection pipe ( 59 ) for sending the liquid refrigerant in the gas-liquid separator ( 51 ) to the suction side of the compressor ( 11 ) and a liquid control valve ( 39 ) for controlling the flow rate of refrigerant through the second injection pipe ( 59 ).  
   
   
       28 . The refrigeration system of  claim 18 , wherein 
 a plurality of said utilization side heat exchangers ( 22   a ,  22   b ,  22   c ) are connected in parallel with each other in the refrigerant circuit ( 10 ), and    the refrigeration system further comprises a plurality of flow control valves ( 61   a ,  61   b ,  61   c ) each for controlling the flow rate of refrigerant flowing into an associated one of the plurality of utilization side heat exchangers ( 22   a ,  22   b ,  22   c ).    
   
   
       29 . The refrigeration system of  claim 18 , wherein carbon dioxide is used as the refrigerant in the refrigerant circuit ( 10 ).