Dual duty compression machine

Abstract

A compression machine includes a refrigerant condenser, an expansion device, a refrigerant evaporator, a first compressor and a second compressor. Each compressor is arranged to receive lower pressure refrigerant vapor from the evaporator and to deliver higher pressure vapor to the condenser independently of the other compressor. The first compressor operates when the compression machine is operating in a first duty mode, for example a water-cooling mode. The second compressor operates when the compression machine is operating in a second duty mode, for example one of a water-heating mode or a brine cooling. The first compressor is selected for optimal performance in the first duty only and the second compressor is selected for optimal performance in the second duty mode only.

1 . A dual duty compression machine for selective operation in one of a first duty mode and a second duty mode comprising:
 a refrigerant condenser, an expansion device, a refrigerant evaporator, and a compression device disposed in a serial refrigerant flow relationship, said compression device including a first compressor and a second compressor, each of said first compressor and said second compressor arranged to receive lower pressure refrigerant vapor from said evaporator and to deliver higher pressure vapor to said condenser independently of the other of said first compressor and said second compressor, said first compressor selected for optimal operation of said compression machine in the first duty mode and said second compressor selected for optimal operation of said compression machine in the second duty mode.   
     
     
         2 . The compression machine as recited in  claim 1  further comprising a control system operatively associated with each of said first compressor and said second compressor for selectively operating said first compressor when operating said compression machine in the first duty mode and for selectively operating said second compressor when operating said compression machine in the second duty mode. 
     
     
         3 . The compression machine as recited in  claim 1  wherein at least one of said first compressor and said second compressor comprises a centrifugal compressor. 
     
     
         4 . The compression machine as recited in  claim 1  further comprising a first drive motor operatively associated with said first compressor only and a second drive motor operatively associated with said second compressor only. 
     
     
         5 . The compression machine as recited in  claim 4  wherein said control system is configured to direct electric power to said first drive motor when operating said compression machine in the first duty mode and direct electric power to said second drive motor when operating said compression machine in the second duty mode. 
     
     
         6 . The compression machine as recited in  claim 1  wherein the first duty mode has a first lift requirement and the second duty mode has a second lift requirement, the second lift requirement being greater than the first lift requirement. 
     
     
         7 . The compression machine as recited in  claim 1  wherein the first duty mode is a water-cooling mode and the second duty mode is a water-heating mode. 
     
     
         8 . The compression machine as recited in  claim 1  wherein the first duty mode is a water-cooling mode and the second duty mode is a brine-cooling mode. 
     
     
         9 . The compression machine as recited in  claim 1  wherein the first duty mode is a water-cooling mode and the second duty mode is one of a water-heating mode and an ice-making brine-cooling mode. 
     
     
         10 . A method for designing a compression machine for selective operation in one of a first duty mode or a second duty mode, the compression machine having a condenser and an evaporator in refrigerant flow communication with the condenser, a first compressor for receiving refrigerant vapor from the evaporator and delivering refrigerant vapor to the condenser, and a second compressor for receiving refrigerant vapor from the evaporator and delivering refrigerant vapor to the condenser, said method comprising the steps of:
 selecting the first compressor to perform optimally in the first duty mode; and   selecting the second compressor to perform optimally in the second duty mode.   
     
     
         11 . The method for designing a compression machine as recited in  claim 10  wherein:
 the step of selecting the first compressor comprises selecting a first centrifugal compressor to perform optimally in the first duty mode only; and 
 the step of selecting the second compressor comprises selecting a second compressor to perform optimally in the second duty mode only. 
 
     
     
         12 . The method as recited in  claim 11  wherein the first duty mode has a first lift requirement and the second duty mode has a second lift requirement, the second lift requirement being greater than the first lift requirement. 
     
     
         13 . The method as recited in  claim 10  wherein the step of selecting the first compressor to perform optimally in the first duty mode comprises selecting the first compressor to perform optimally in a water-cooling mode; and the step of selecting the second compressor to perform optimally in the second duty mode comprises selecting the second compressor to perform optimally in one of a water-heating mode or a brine-cooling mode. 
     
     
         14 . A method for operating a compression machine for selectively cooling water or heating water, the compression machine having a condenser and an evaporator in refrigerant flow communication with the condenser, a first compressor for receiving refrigerant vapor from the evaporator and delivering refrigerant vapor to the condenser, and a second compressor for receiving refrigerant vapor from the evaporator and delivering refrigerant vapor to the condenser, said method comprising the steps of:
 selectively operating the compression machine in one of a water cooling mode or a water heating mode;   operating the first compressor only when operating the compression machine in a water cooling mode; and   operating the second compressor only when operating the compression machine in a water heating mode.   
     
     
         15 . The method for operating a compression machine as recited in  claim 14  wherein the first compressor is selected to perform optimally in a water chilling mode and the second compressor is selected to perform optimally in a water heating mode. 
     
     
         16 . The method for operating a compression machine as recited in  claim 15  wherein at least one of the first compressor and the second compressor comprises a centrifugal compressor. 
     
     
         17 . The compression machine as recited in  claim 1  wherein said first compressor is selected for operation of the compression machine for providing chilled water passing from the refrigerant evaporator at a temperature in the range of from about 2° C. to about 12° C. (about 35° F. to about 54° F.). 
     
     
         18 . The compression machine as recited in  claim 1  wherein said second compressor is selected for operation of the compression machine for providing heated water passing from the refrigerant condenser at a temperature in the range of from about 40° C. to about 60° C. (about 104° F. to about 140° F.).