Thermodynamic system provided with a plurality of compressors

Abstract

The thermodynamic system includes a circuit for circulating a refrigerant including a compression device including a first and a second compressors each including a sealed enclosure including a low-pressure portion containing a motor and an oil pan positioned at the bottom of the enclosure, and a refrigerant intake opening leading into the low-pressure portion, a refrigerant dispensing device arranged to connect an evaporator to the intake opening of the first compressor, an oil level equalization conduit putting the oil pans of the first and second compressors in communication, a connecting device putting the low-pressure portion of the first compressor in communication with the intake opening of the second compressor, and control means arranged to control the starting and stopping of the first and second compressors according to four control modes.

1 . A thermodynamic system, comprising:
 a circuit for circulating a refrigerant successively including a condenser, an expander, an evaporator and a compression device connected in series, the compression device comprising at least one first compressor and one second compressor mounted in parallel, each compressor comprising a sealed enclosure including on the one hand a low-pressure portion containing a motor and an oil pan positioned at the bottom of the enclosure, and on the other hand a refrigerant intake opening leading into the low-pressure portion, and   a refrigerant dispensing device arranged to connect the evaporator to an intake opening of the first compressor,   an oil level equalization conduit putting the oil pans of the first and second compressors in communication,   a connecting device putting the low-pressure portion of the first compressor in communication with the intake opening of the second compressor, such that all of the refrigerant penetrating the low-pressure portion of the second compressor comes from the low-pressure portion of the first compressor, and   control means arranged to control the starting and stopping of the first and second compressors,   wherein the control means are arranged to control the starting and stopping of the first and second compressors according to:   a first control mode, in which the control means control the starting of the first and second compressors,   a second control mode, in which the control means control the starting of the first compressor and the stopping of the second compressor,   a third control mode, in which the control means control the stopping of the first compressor and the starting of the second compressor, and   a fourth control mode, in which the control means control the stopping of the first and second compressors,   and the oil level equalization conduit includes an end portion turned toward the first compressor side and protruding inside the sealed enclosure of said first compressor, said end portion including an end wall extending transversely to the longitudinal direction of said end portion and an opening formed above the end wall such that, when the oil level in the oil pan of the first compressor extends above the upper level of said end wall, oil flows through said opening toward the second compressor.   
     
     
         2 . The thermodynamic system according to  claim 1 , wherein at least one of the first and second compressors is a variable-capacity compressor, or wherein the first and second compressors are fixed-capacity compressors and have a capacity ratio comprised between 1.5 and 3. 
     
     
         3 . The thermodynamic system according to  claim 1 , wherein the oil level equalization conduit is arranged and sized such that, when the system is in the overheated steady state, an upper portion of the flow cross-section of the equalization conduit is situated above the oil levels in the oil pans of the first and second compressors so as simultaneously to allow the transfer of oil and refrigerant between the first and second compressors. 
     
     
         4 . The thermodynamic system according to  claim 1 , wherein the end portion of the oil level equalization conduit turned toward the first compressor side includes an oil return opening formed in a lower part of said end portion situated below the upper level of the end wall. 
     
     
         5 . The thermodynamic system according to  claim 1 , wherein one of the first and second compressors is a variable-capacity compressor, and the other of the first and second compressors is a fixed-capacity compressor. 
     
     
         6 . The thermodynamic system according to  claim 5 , wherein the thermodynamic system comprises controlling means arranged to modulate the capacity of the variable-capacity compressor between a minimum capacity value and a maximum capacity value. 
     
     
         7 . The thermodynamic system according to  claim 1 , wherein the first and second compressors are fixed-capacity compressors, the capacity of the first compressor being larger than that of the second compressor. 
     
     
         8 . The thermodynamic system according to  claim 1 , wherein the compression device comprises a third compressor mounted in series with the first compressor and upstream therefrom, the dispensing device comprising a first dispensing conduit putting the evaporator in communication with the intake opening of the third compressor, and the second dispensing conduit putting the low-pressure portion of the third compressor in communication with the intake opening of the first compressor such that all of the refrigerant penetrating the low-pressure portion of the first compressor comes from the low-pressure portion of the third compressor. 
     
     
         9 . The thermodynamic system according to  claim 1 , wherein the compression device comprises a fourth compressor mounted in parallel with the second compressor, the connecting device comprising a connecting conduit connected to the low-pressure portion of the first compressor, a first bypass conduit putting the connecting conduit in communication with the intake opening of the second compressor, and a second bypass conduit putting the connecting conduit in communication with the intake opening of the fourth compressor. 
     
     
         10 . The thermodynamic system according to  claim 1 , wherein the connecting device comprises a connecting conduit putting the low-pressure portion of the first compressor in communication with the intake opening of the second compressor. 
     
     
         11 . The thermodynamic system according to  claim 10 , wherein the end of the connecting conduit turned toward the first compressor protrudes inside the enclosure of the first compressor. 
     
     
         12 . The thermodynamic system according to  claim 1 , wherein each compressor is a scroll refrigeration compressor. 
     
     
         13 . The thermodynamic system according to  claim 12 , wherein the first compressor comprises a fixed volute and a moving volute following an orbital movement, a body on which the moving volute bears, an intermediate casing fixed on the body and inside which the motor is mounted, and at least one oil return conduit extending at least partially over the outer wall of the intermediate casing, the oil return conduit including a first end turned toward the body and inserted in an opening formed in the body, and a second end leading near the oil pan. 
     
     
         14 . The thermodynamic system according to  claim 1 , wherein at least the first compressor comprises first deflecting means positioned in the sealed enclosure of said first compressor and whereof at least one portion is positioned across from the intake opening of said first compressor, the first deflecting means being arranged to orient at least a portion of the refrigerant penetrating the low-pressure portion of the first compressor along at least one portion of the inner wall of the sealed enclosure of said first compressor. 
     
     
         15 . The thermodynamic system according to  claim 1 , wherein at least the first compressor comprises second deflecting means positioned in the sealed enclosure of said first compressor and whereof at least one portion is positioned across from the end of the connecting device turned toward the first compressor side, the second deflecting means being arranged to orient the refrigerant penetrating the low-pressure portion of the first compressor following an ascending, then descending movement before the flow thereof through the connecting device.