Refrigerating apparatus

Abstract

A refrigerating apparatus having a plurality of compressors includes an injection circuit ( 40 ) which includes a first injection pipe ( 37 ) branched from a first refrigerant pipe ( 32 ) of a refrigerant circuit ( 10 ) and branch injection pipes ( 37 a, 37 b, 37 c ) branched from the first injection pipe ( 37 ), a subcooling pressure-reducing valve ( 29 ) provided to the first injection pipe ( 37 ), and flow rate adjusting valves ( 30 a, 30 b, 30 c ) provided to the branch injection pipes ( 37 a, 37 b, 37 c ), respectively, thereby providing an appropriate refrigerant injection to each of the compressors.

1 . A refrigerating apparatus comprising: a refrigerant circuit ( 10 ) which has a plurality of compressors ( 21   a ,  21   b ,  21   c ) and which performs a vapor compression refrigeration cycle; an injection circuit ( 40 ) which has a main pipe ( 37 ) branched from a high pressure line ( 33 ) of the refrigerant circuit ( 10 ) and branch pipes ( 37   a ,  37   b ,  37   c ) branched from the main pipe ( 37 ), and in which the branch pipes ( 37   a ,  37   b ,  37   c ) are connected to intermediate ports ( 5 ,  6 ,  7 ) of the compressors ( 21   a,    21   b,    21   c ), respectively; and a pressure-reducing mechanism ( 29 ) provided to the main pipe ( 37 ) of the injection circuit ( 40 ), wherein at least one of the plurality of compressors ( 21   a ,  21   b ,  21   c ) is a variable displacement compressor ( 21   a ), and a flow rate adjusting mechanism ( 30   a ,  30   b ,  30   c ) is provided at least to the branch pipe ( 37   a ,  37   b ,  37   c ) of the variable displacement compressor ( 21   a ). 
     
     
         2 . The refrigerating apparatus of  claim 1 , wherein
 the flow rate adjusting mechanism ( 30   a ,  30   b ,  30   c ) is provided to each of the branch pipes ( 37   a ,  37   b ,  37   c ) of the injection circuit ( 40 ).   
     
     
         3 . The refrigerating apparatus of  claim 1 , comprising
 a subcooling heat exchanger ( 28 ) having a reduced-pressure side flow path ( 28   b ) through which a refrigerant decompressed by the pressure-reducing mechanism ( 29 ) flows and a high pressure side flow path ( 28   a ) through which a high pressure refrigerant of the refrigerant circuit ( 10 ) flows, wherein   the reduced-pressure side flow path ( 28   b ) is connected to the main pipe ( 37 ) of the injection circuit ( 40 ), and the high pressure side flow path ( 28   a ) is connected to the high pressure line ( 33 ) of the refrigerant circuit ( 10 ).   
     
     
         4 . The refrigerating apparatus of  claim 1 , comprising: oil separators ( 38   a ,  38   b ,  38   c ) respectively provided to discharge pipes ( 22   a ,  22   b ,  22   c ) of the compressors ( 21   a ,  21   b ,  21   c ), for separating a refrigerating machine oil from a discharge refrigerant discharged from the compressors ( 21   a ,  21   b ,  21   c ); oil discharge pipes ( 39   a ,  39   b ,  39   c ) connected to the oil separators ( 38   a ,  38   b ,  38   c ); and an oil return circuit ( 39 ) of which one end side is connected to the oil discharge pipes ( 39   a ,  39   b ,  39   c ) and of which the other end side is connected to a branch pipe branched from the injection circuit ( 40 ), for returning the refrigerating machine oil from the oil discharge pipes ( 39   a ,  39   b ,  39   c ) to the compressors ( 21   a ,  21   b ,  21   c ). 
     
     
         5 . The refrigerating apparatus of  claim 1 , wherein
 the flow rate adjusting mechanism ( 30   a ,  30   b ,  30   c ) is a flow rate adjusting valve whose degree of opening is variable.   
     
     
         6 . The refrigerating apparatus of  claim 1 , wherein
 the flow rate adjusting mechanism ( 30   a ,  30   b ,  30   c ) is an on/off valve.   
     
     
         7 . The refrigerating apparatus of  claim 1 , wherein
 the plurality of compressors ( 21   a ,  21   b ,  21   c ) include a variable displacement compressor ( 21   a ) and a fixed displacement compressor ( 21   b ,  21   c ), and   the flow rate adjusting mechanism ( 30   a ) provided to the branch pipe ( 37   a ) connected to the intermediate port ( 5 ) of the variable displacement compressor ( 21   a ) is a flow rate adjusting valve whose degree of opening is variable, and the flow rate adjusting mechanism ( 30   b ,  30   c ) provided to the branch pipe ( 37   b ,  37   c ) connected to the intermediate port ( 6 ,  7 ) of the fixed displacement compressor ( 21   b ,  21   c ) is an on/off valve.   
     
     
         8 . The refrigerating apparatus of  claim 1 , comprising
 a discharge refrigerant temperature detection mechanism ( 61 ) for detecting a temperature of a discharge refrigerant discharged from the compressors ( 21   a ,  21   b ,  21   c ), and   a control mechanism ( 9 ) for adjusting a degree of opening of each of the flow rate adjusting mechanisms ( 30   a ,  30   b ,  30   c ) such that a value detected by the discharge refrigerant temperature detection mechanism ( 61 ) falls within a predetermined temperature range.   
     
     
         9 . The refrigerating apparatus of  claim 3 , comprising
 a discharge condition detection mechanism ( 61 ,  66 ) for detecting at least one of a discharge temperature and a discharge superheat of each of the compressors ( 21   a ,  21   b ,  21   c ),   a discharge condition setting mechanism ( 76 ) for setting a discharge target value Tm, Tgshm for the at least one of the discharge temperature and the discharge superheat of each of the compressors ( 21   a ,  21   b ,  21   c ),   an intermediate superheat detection mechanism ( 75 ) for detecting a superheat of an intermediate-pressure refrigerant having passed through the reduced-pressure side flow path ( 28   b ) of the subcooling heat exchanger ( 28 ),   an intermediate superheat setting mechanism ( 77 ) for setting an intermediate superheat target value Tgshm for the superheat of the intermediate-pressure refrigerant having passed through the reduced-pressure side flow path ( 28   b ) of the subcooling heat exchanger ( 28 ),   a first discharge target control section ( 56   a ) for changing a degree of opening of the pressure-reducing mechanism ( 29 ) such that a maximum detection value Ttd, which is a maximum value among values Td detected by the discharge condition detection mechanisms ( 61 ,  66 ) for the respective compressors ( 21   a,    21   b,    21   c ), becomes the discharge target value Tm, Tgshm,   an intermediate superheat control section ( 60 ) for changing the degree of opening of the pressure-reducing mechanism ( 29 ) such that a value Tgsh detected by the intermediate superheat detection mechanism ( 75 ) becomes the intermediate superheat target value Tgshm, and   a first control section ( 16 ) for exerting control, if a refrigerant condition value of the refrigerant in the refrigerant circuit ( 10 ) is in a predetermined range, by selecting the first discharge target control section ( 56   a ) or the intermediate superheat control section ( 60 ) based on the refrigerant condition value.   
     
     
         10 . The refrigerating apparatus of  claim 9 , wherein
 the first control section ( 16 ) is configured to exert control by selecting the first discharge target control section ( 56   a ) if the maximum detection value Ttd of the discharge condition detection mechanism ( 61 ,  66 ) is larger than the discharge target value Tm.   
     
     
         11 . The refrigerating apparatus of  claim 9 , wherein
 the first control section ( 16 ) is configured to exert control by selecting the intermediate superheat control section ( 60 ) if the maximum detection value Ttd of the discharge condition detection mechanism ( 61 ,  66 ) is equal to or smaller than the discharge target value Tm.   
     
     
         12 . The refrigerating apparatus of  claim 9 , wherein
 the first control section ( 16 ) is configured to exert control by selecting the intermediate superheat control section ( 60 ) if the maximum detection value Ttd of the discharge condition detection mechanism ( 61 ,  66 ) continues to decrease during a predetermined time t 1 .   
     
     
         13 . The refrigerating apparatus of  claim 9 , comprising
 a first superheat avoidance control section ( 78   a ) for having the degree of opening of the pressure-reducing mechanism ( 29 ) greater than the present degree of opening of the pressure-reducing mechanism ( 29 ),   a first wet avoidance control section ( 79   a ) for having the degree of opening of the pressure-reducing mechanism ( 29 ) smaller than the present degree of opening of the pressure-reducing mechanism ( 29 ), and   an avoidance control section ( 58 ) for exerting control, if the refrigerant condition value of the refrigerant in the refrigerant circuit ( 10 ) exceeds the predetermined range, by selecting the first superheat avoidance control section ( 78   a ) or the first wet avoidance control section ( 79   a ) until the refrigerant condition value is in the predetermined range.   
     
     
         14 . The refrigerating apparatus of  claim 13 , wherein
 the avoidance control section ( 58 ) is configured to exert control by selecting the first superheat avoidance control section ( 78   a ) in at least one of the cases where the value Td detected by the discharge condition detection mechanism ( 61 ,  66 ) is even larger than an upper threshold value Tdmax set larger than the discharge target value Tm, and where the value Tgsh detected by the intermediate superheat detection mechanism ( 75 ) is even larger than an upper threshold value Tgshmax set larger than the intermediate superheat target value Tgshm.   
     
     
         15 . The refrigerating apparatus of  claim 13 , wherein
 the avoidance control section ( 58 ) is configured to exert control by selecting the first wet avoidance control section ( 79   a ) in at least one of the cases where the value Td detected by the discharge condition detection mechanism ( 61 ,  66 ) is even smaller than a lower threshold value Tdmin set smaller than the discharge target value Tm, and where the value Tgsh detected by the intermediate superheat detection mechanism ( 75 ) is even smaller than a lower threshold value Tgshmin set smaller than the intermediate superheat target value Tgshm.   
     
     
         16 . The refrigerating apparatus of  claim 9 , comprising
 a second control section ( 17 ) for changing a degree of opening of the flow rate adjusting mechanism ( 30   a ,  30   b ,  30   c ) such that the values Td detected by the discharge condition detection mechanisms ( 61 ,  66 ) for the respective compressors ( 21   a ,  21   b ,  21   c ) are approximate to each other.   
     
     
         17 . The refrigerating apparatus of  claim 3 , wherein
 the plurality of compressors ( 21   a ,  21   b ,  21   c ) include a first compressor ( 21   a ,  21   b ) and a second compressor ( 21   c ),   a low pressure line of the refrigerant circuit ( 10 ) includes a first low pressure line ( 102 ) for connecting between a suction side of the first compressor ( 21   a ,  21   b ) and a cooling heat exchanger ( 53   b ,  81 ) which is provided in the refrigerant circuit ( 10 ) and which provides cooling for a storage room, and a second low pressure line ( 101 ) for connecting between a suction side of the second compressor ( 21   c ) and an air-conditioning heat exchanger ( 53   a ) which is provided in the refrigerant circuit ( 10 ) and which provides air conditioning for an indoor space,   the refrigerating apparatus includes low-level pressure detection mechanisms ( 120 ,  121 ) for detecting a pressure of a low pressure refrigerant flowing in each of the first and second low pressure lines ( 102 ,  101 ), an intermediate pressure detection mechanism ( 71 ) for detecting a pressure of an intermediate-pressure refrigerant having been decompressed by the pressure-reducing mechanism ( 29 ), an intermediate superheat detection mechanism ( 75 ) for detecting a superheat of the intermediate-pressure refrigerant having passed through the reduced-pressure side flow path ( 28   b ) of the subcooling heat exchanger ( 28 ), and an intermediate superheat setting mechanism ( 77 ) for setting an intermediate superheat target value Tgshm for the superheat of the intermediate-pressure refrigerant having passed through the reduced-pressure side flow path ( 28   b ) of the subcooling heat exchanger ( 28 ), and   the refrigerating apparatus includes
 an intermediate pressure control section ( 59 ) for changing a degree of opening of the pressure-reducing mechanism ( 29 ) such that a value MP detected by the intermediate pressure detection mechanism ( 71 ) becomes larger than values LP of the low pressure lines ( 102 ,  101 ) detected by the low-level pressure detection mechanisms ( 120 ,  121 ), 
 an intermediate superheat control section ( 60 ) for changing the degree of opening of the pressure-reducing mechanism ( 29 ) such that a value Tgsh detected by the intermediate superheat detection mechanism ( 75 ) becomes the intermediate superheat target value Tgshm, and 
   a third control section ( 18 ) for exerting control by selecting the intermediate pressure control section ( 59 ) or the intermediate superheat control section ( 60 ), based on an operating condition of the plurality of compressors ( 21   a ,  21   b ,  21   c ).   
     
     
         18 . The refrigerating apparatus of  claim 17 , wherein
 the third control section ( 18 ) is configured to exert control by selecting the intermediate pressure control section ( 59 ) if the first compressor ( 21   a ,  21   b ) and the second compressor ( 21   c ) are activated together.   
     
     
         19 . The refrigerating apparatus of  claim 17 , wherein
 the third control section ( 18 ) is configured to exert control by selecting the intermediate superheat control section ( 60 ) if one of the first compressor ( 21   a,    21   b ) and the second compressor ( 21   c ) is actuated.   
     
     
         20 . The refrigerating apparatus of  claim 17 , comprising
 a discharge condition detection mechanism ( 61 ,  66 ) for detecting at least one of a discharge temperature and a discharge superheat of each of the compressors ( 21   a ,  21   b ,  21   c ), and a discharge condition setting mechanism ( 76 ) for setting a discharge target value Tm for the at least one of the discharge temperature and the discharge superheat of each of the compressors ( 21   a ,  21   b ,  21   c ),   a second discharge target control section ( 56   b ) for changing a degree of opening ,of the flow rate adjusting mechanism ( 30   a ,  30   b ,  30   c ) such that a value Td detected by the discharge condition detection mechanism ( 61 ,  66 ) becomes the discharge target value Tm,   a second superheat avoidance control section ( 78   b ) for having the degree of opening of the flow rate adjusting mechanism ( 30   a ,  30   b ,  30   c ) greater than the present degree of opening of the flow rate adjusting mechanism ( 30   a ,  30   b ,  30   c ),   a second wet avoidance control section ( 79   b ) for having the degree of opening of the flow rate adjusting mechanism ( 30   a ,  30   b ,  30   c ) smaller than the present degree of opening of the flow rate adjusting mechanism ( 30   a ,  30   b ,  30   c ),   a fourth control section ( 19 ) for exerting control by selecting the second discharge target control section ( 56   b ) if a refrigerant condition value of the refrigerant in the refrigerant circuit ( 10 ) is in a predetermined range, and selecting the second superheat avoidance control section ( 78   b ) or the second wet avoidance control section ( 79   b ) if the refrigerant condition value exceeds the predetermined range.   
     
     
         21 . The refrigerating apparatus of  claim 20 , wherein
 the fourth control section ( 19 ) is configured to exert control by selecting the second superheat avoidance control section ( 78   b ) in at least one of the cases where the value Td detected by the discharge condition detection mechanism ( 61 ,  66 ) is even larger than an upper threshold value Tdmax set larger than the discharge target value Tm, or where the value Tgsh detected by the intermediate superheat detection mechanism ( 75 ) is even larger than an upper threshold value Tgshmax set larger than the intermediate superheat target value Tgshm.   
     
     
         22 . The refrigerating apparatus of  claim 20 , wherein
 the fourth control section ( 19 ) is configured to exert control by selecting the second wet avoidance control section ( 79   b ) in at least one of the cases where the value Td detected by the discharge condition detection mechanism ( 61 ,  66 ) is even smaller than a lower threshold value Tdmin set smaller than the discharge target value Tm, or where the value Tgsh detected by the intermediate superheat detection mechanism ( 75 ) is even smaller than a lower threshold value Tgshmin set smaller than the intermediate superheat target value Tgshm.   
     
     
         23 . The refrigerating apparatus of  claim 20 , wherein
 the fourth control section ( 19 ) is configured to exert control by selecting the second discharge target control section ( 56   b ) if the value Td detected by the discharge condition detection mechanism ( 61 ,  66 ) is equal to or larger than a lower threshold value Tdmin set smaller than the discharge target value Tm, and equal to or smaller than an upper threshold value Tdmax set larger than the discharge target value Tm.