Refigeration system

Abstract

In a refrigeration system having a refrigerant circuit ( 20 ) that is constructed in such a way that a plurality of lines of refrigeration circuits ( 70, 80 ) having refrigeration heat exchangers ( 72, 84 ) respectively are connected to an outdoor circuit ( 30 ) provided with an outdoor heat exchanger ( 32 ) and a compression mechanism ( 31 ) and conducts a vapor compression type refrigeration cycle, at least one of the lines of refrigeration circuits ( 80 ) having an auxiliary compressor ( 85 ) connected in series to the refrigeration heat exchanger ( 84 ), in order to respond to a variety of patterns of defrosting operations without providing a defrosting mechanism other than the refrigerant circuit ( 20 ), there is provided a hot gas introduction passage ( 46, 89 ) for selectively introducing gas refrigerant discharged from the compression mechanism ( 31 ) of the outdoor circuit ( 30 ) into at least one of the plurality of refrigeration heat exchangers ( 72, 84 ) and a defrosting operation of conducting a refrigeration cycle by using the refrigeration heat exchanger ( 72, 84 ) as a condenser can be performed.

1 . A refrigeration system having a refrigerant circuit ( 20 ) that is constructed in such a way that a plurality of lines of refrigeration circuits ( 70 ,  80 ) having refrigeration heat exchangers ( 72 ,  84 ) respectively are connected to an outdoor circuit ( 30 ) provided with an outdoor heat exchanger ( 32 ) and a compression mechanism ( 31 ) and conducts a vapor compression type refrigeration cycle, at least one of the lines of refrigeration circuits ( 80 ) having an auxiliary compressor ( 85 ) connected in series to the refrigeration heat exchanger ( 84 ), the refrigeration system comprising:
 a hot gas introduction passage ( 46 ,  89 ), ( 100 ,  102 ) for selectively introducing gas refrigerant discharged from the compression mechanism ( 31 ) of the outdoor circuit ( 30 ) into at least one of the plurality of refrigeration heat exchangers ( 72 ,  84 ); and   a defrosting path ( 25 ) capable of performing a defrosting operation of conducting a refrigeration cycle by using that refrigeration heat exchanger ( 72 ,  84 ) as a condenser.   
   
   
       2 . The refrigeration system according to  claim 1 , wherein the outdoor circuit ( 30 ) has a first refrigeration circuit ( 70 ) and a second refrigeration circuit ( 80 ) connected thereto in parallel, the first refrigeration circuit ( 70 ) having a first refrigeration heat exchanger ( 72 ), the second refrigeration circuit ( 80 ) having a second refrigeration heat exchanger ( 84 ) and the auxiliary compressor ( 85 ). 
   
   
       3 . The refrigeration system according to  claim 1 , wherein the outdoor circuit ( 30 ) has a plurality of refrigeration circuits ( 80 ) connected thereto in parallel, each of the plurality of refrigeration circuits ( 80 ) having the refrigeration heat exchanger ( 84 ) and the auxiliary compressor ( 85 ). 
   
   
       4 . The refrigeration system according to  claim 1 , wherein:
 the outdoor circuit ( 30 ) has an air heat exchanger circuit ( 60 ) connected thereto, the air heat exchanger circuit ( 60 ) having an air heat exchanger ( 62 ) for adjusting temperature of air; and   a first defrosting operation and a second defrosting operation can be performed, the first defrosting operation using the refrigeration heat exchangers ( 72 ,  84 ) as condensers and using the air heat exchanger ( 62 ) as an evaporator, the second defrosting operation using the refrigeration heat exchangers ( 72 ,  84 ) as condensers and using the outdoor heat exchanger ( 32 ) as an evaporator.   
   
   
       5 . The refrigeration system according to  claim 1 , wherein the hot gas introduction passage ( 46 ,  89 ) has a high stage side hot gas passage ( 46 ) and a low stage side hot gas passage ( 89 ), the high stage side hot gas passage ( 46 ) being connected to a discharge line ( 45 ) of the compression mechanism ( 31 ) of the outdoor circuit ( 30 ) and to a base pipe ( 42 ) of a low-pressure gas line of the respective refrigeration circuits ( 70 ,  80 ) and allowing a refrigerant flow to the respective refrigeration heat exchangers ( 72 ,  84 ) from the discharge line ( 45 ) of the compression mechanism ( 31 ) at a time of a defrosting operation, the low stage side hot gas passage ( 89 ) being connected to a discharge line ( 22   b ) and a suction line ( 88 ) of the auxiliary compressor ( 85 ) and allowing a refrigerant flow to the refrigeration heat exchanger ( 84 ) connected to the auxiliary compressor ( 85 ) from the discharge line ( 22   b ) of the auxiliary compressor ( 85 ) at the time of the defrosting operation. 
   
   
       6 . The refrigeration system according to  claim 5 , wherein:
 the compression mechanism ( 31 ) of the outdoor circuit ( 30 ) includes: a first compressor ( 31   a ), a second compressor ( 31   b ), and a third compressor ( 31   c ), which are connected in parallel; a four-way switching valve ( 37 ) connected to an suction side of the compression mechanism ( 31 ); a high stage side opening/opening valve (SV 1 ) disposed in the high stage side hot gas passage ( 46 ); and a low stage side opening/opening valve (SV 2 ) disposed in the low stage side hot gas passage ( 89 ), the first compressor ( 31   a ) having its suction pipe ( 41   a ) connected to a first port (P 1 ) of the four-way switching valve ( 37 ) via a check valve (CV 1 ) for prohibiting a refrigerant flow to the first compressor ( 31   a ),   the second compressor ( 31   b ) having its suction pipe ( 41   b ) connected to a second port (P 2 ) of the four-way switching valve ( 37 ),   the third compressor ( 31   c ) having its suction pipe ( 41   c ) connected to a third port (P 3 ) of the four-way switching valve ( 37 ) via a check valve (CV 2 ) for prohibiting a refrigerant flow to the third compressor ( 31   c ),   the compression mechanism ( 31 ) having its high-pressure introduction pipe ( 47 ) communicating with a high pressure line connected to a fourth port (P 4 ) of the four-way switching valve ( 37 );   the high stage side hot gas passage ( 46 ) is connected to the suction pipe ( 41   a ) of the first compressor ( 31   a ); and   the four-way switching valve ( 37 ) is constructed so as to be able to switch between a first state in which the first port (P 1 ) communicates with the second port (P 2 ) and in which the third port (P 3 ) communicates with the fourth port (P 4 ) and a second state in which the first port (P 1 ) communicates with the fourth port (P 4 ) and in which the second port (P 2 ) communicates with the third port (P 3 ).   
   
   
       7 . The refrigeration system according to  claim 5 , wherein:
 the compression mechanism ( 31 ) of the outdoor circuit ( 30 ) includes: a first compressor ( 31   a ), a second compressor ( 31   b ), and a third compressor ( 31   c ), which are connected in parallel; a four-way switching valve ( 37 ) connected to a suction side of the compression mechanism ( 31 ); and a low stage side opening/opening valve (SV 2 ) disposed in the low stage side hot gas passage ( 89 ),   the first compressor ( 31   a ) having its suction pipe  41   a  connected to a first port (P 1 ) of the four-way switching valve ( 37 ),   the second compressor ( 31   b ) having its suction pipe ( 41   b ) connected to a second port (P 2 ) of the four-way switching valve ( 37 ),   the third compressor ( 31   c ) having its suction pipe ( 41   c ) connected to a third port (P 3 ) of the four-way switching valve ( 37 ) via a check valve (CV 2 ) for prohibiting a refrigerant flow to the third compressor ( 31   c );   the high stage side hot gas passage ( 46 ) is connected to a fourth port (P 4 ) of the four-way switching valve ( 37 ); and   the four-way switching valve ( 37 ) is constructed so as to be able to switch between a first state in which the first port (P 1 ) communicates with the fourth port (P 4 ) and in which the second port (P 2 ) communicates with the third port (P 3 ) and a second state in which the first port (P 1 ) communicates with the second port (P 2 ) and in which the third port (P 3 ) communicates with the fourth port (P 4 ).   
   
   
       8 . The refrigeration system according to  claim 1 , wherein the hot gas passage ( 46 ,  89 ) includes a first introduction passage ( 96 ) and a second introduction passage ( 97 ), the first introduction passage ( 96 ) introducing gas refrigerant discharged from the compression mechanism ( 31 ) of the outdoor circuit ( 30 ) into the auxiliary compressor ( 85 ), the second introduction passage ( 97 ) introducing gas refrigerant discharged from the auxiliary compressor ( 85 ) into the refrigeration heat exchanger ( 84 ). 
   
   
       9 . The refrigeration system according to  claim 8 , wherein:
 the second introduction passage ( 97 ) is connected to the compression mechanism ( 31 ) of the outdoor circuit ( 30 ) and to the refrigeration heat exchanger ( 84 );   the first introduction passage ( 96 ) is branched from the second introduction passage ( 97 ) and is connected to the auxiliary compressor ( 85 ) so as to introduce part of gas refrigerant discharged from the compression mechanism ( 31 ) of the outdoor circuit ( 30 ) into the auxiliary compressor  85 ; and   the second introduction passage ( 97 ) has a discharge pipe ( 98 ) of the auxiliary compressor ( 85 ) connected to its portion closer to the compression mechanism ( 31 ) of the outdoor circuit ( 30 ).   
   
   
       10 . The refrigeration system according to  claim 9 , comprising a liquid injection passage ( 99 ) for introducing part of liquid refrigerant flowing out of the refrigeration heat exchanger ( 84 ) into the auxiliary compressor ( 85 ). 
   
   
       11 . The refrigeration system according to  claim 9 , wherein the auxiliary compressor ( 85 ) is constructed of a variable displacement compressor. 
   
   
       12 . The refrigeration system according to  claim 1 , wherein the hot gas introduction passage ( 100 ,  102 ) is directly connected to a discharge line ( 45 ) of the compression mechanism ( 31 ) of the outdoor circuit ( 30 ) and to at least one of gas side piping ( 110 ,  112 ) of the refrigeration heat exchangers ( 72 ,  84 ). 
   
   
       13 . The refrigeration system according to  claim 12 , wherein the hot gas introduction passage ( 100 ,  102 ) is connected to the discharge line ( 45 ) of the compression mechanism ( 31 ) of the outdoor circuit ( 30 ) and to the gas side piping ( 110 ,  112 ) of the plurality of refrigeration heat exchangers ( 72 ,  84 ) and is provided with a switching mechanism ( 103 ) capable of switching or selecting the plurality of refrigeration heat exchangers ( 72 ,  84 ). 
   
   
       14 . The refrigeration system according to  claim 12 , wherein the hot gas introduction passage ( 100 ,  102 ) is provided with a flow control mechanism ( 101 ).