Modular chiller with pumped refrigerant economizer

Abstract

A mixed mode modular cooling system can include two or more mixed mode refrigerant loops and plumbing to permit a working fluid to circulate through at least a portion of the loops. Each mixed mode refrigerant loop can include an evaporator, a condenser, a pump to pump a refrigerant through the evaporator and the condenser, and a compressor configured to compress the refrigerant between the evaporator and the condenser. As cooling demand varies, each mixed mode refrigerant loop can be brought online and operated in either compressed refrigerant mode or pumped refrigerant mode.

What is claimed is: 
     
         1 . A method of operating a modular cooling system comprising:
 monitoring a cooling demand;   starting a first mixed mode refrigerant loop in pumped refrigerant mode, as the cooling demand rises to a first demand level;   operating the first mixed mode refrigerant loop in pumped refrigerant mode and starting a second mixed mode refrigerant loop in pumped refrigerant mode, as the cooling demand rises from the first demand level to a second demand level;   operating the second mixed mode refrigerant loop in pumped refrigerant mode and switching the first mixed mode refrigerant loop from pumped refrigerant mode to compressed refrigerant mode, as the cooling demand rises from the second demand level to a third demand level; and   operating the first mixed mode refrigerant loop in compressed refrigerant mode and switching the second mixed mode refrigerant loop from pumped refrigerant mode to compressed refrigerant mode, as the cooling demand rises from the third demand level to a fourth demand level.   
     
     
         2 . The method of  claim 1 , wherein starting the first mixed mode refrigerant loop in pumped refrigerant mode comprises:
 opening a first flow valve; and   starting a first pump, thereby pumping a first two-phase refrigerant through a first condenser and a first evaporator.   
     
     
         3 . The method of  claim 2 , wherein starting the second mixed mode refrigerant loop in pumped refrigerant mode comprises:
 opening a second flow valve; and   starting a second pump, thereby pumping a second two-phase refrigerant through a second condenser and a second evaporator.   
     
     
         4 . The method of  claim 1 , wherein switching the first mixed mode refrigerant loop from pumped refrigerant mode to compressed refrigerant mode comprises
 leaving the first flow valve open;   stopping the first pump; and   starting a first compressor, thereby compressing the first two-phase refrigerant between the first evaporator and the first condenser.   
     
     
         5 . The method of  claim 4 , wherein switching the second mixed mode refrigerant loop from pumped refrigerant mode to compressed refrigerant mode comprises
 leaving the second flow valve open;   stopping the second pump; and   starting a second compressor, thereby compressing the second two-phase refrigerant between the second evaporator and the second condenser.   
     
     
         6 . The method of  claim 1 , further comprising, as the cooling demand varies between the first demand level and the second demand level, varying a first pump speed of a first pump of the first mixed mode refrigerant loop; wherein the second demand level indicates greater cooling demand than the first demand level; wherein the third demand level indicates greater cooling demand than the second demand level; and wherein the fourth demand level indicates greater cooling demand than the third demand level. 
     
     
         7 . The method of  claim 6 , further comprising, as the cooling demand varies between the second demand level and the third demand level;
 running the first pump at a first maximum pump speed, wherein the first maximum pump speed is the first pump's maximum rated speed; and   varying a second pump speed of a second pump of the second mixed mode refrigerant loop.   
     
     
         8 . The method of  claim 7 , further comprising, as the cooling demand varies between the third demand level and the fourth demand level;
 running the second pump at a second maximum pump speed, wherein the second maximum pump speed is the second pump's maximum rated speed; and   varying a first compressor speed of a first compressor of the first mixed mode refrigerant loop.   
     
     
         9 . The method of  claim 7 , further comprising, as the cooling demand varies between the third demand level and the fourth demand level;
 running a first compressor of the first mixed mode refrigerant loop at a first maximum compressor speed, wherein the first maximum compressor speed is the first compressor's maximum rated speed; and   varying the second pump speed of the second pump.   
     
     
         10 . The method of  claim 9 , further comprising, as the cooling demand varies above the fourth demand level;
 running the first compressor at the first maximum compressor speed; and   varying a second compressor speed of a second compressor of the second mixed mode refrigerant loop.   
     
     
         11 . A method of operating a modular cooling system comprising:
 monitoring a cooling demand;   operating, as the cooling demand varies between a first demand level and a second demand level, a first mixed mode refrigerant loop in pumped refrigerant mode, while isolating a second mixed mode refrigerant loop;   operating, as the cooling demand varies between the second demand level and a third demand level, both the first mixed mode refrigerant loop and the second mixed mode refrigerant loop in pumped refrigerant mode;   operating, as the cooling demand varies between the third demand level and a fourth demand level, the first mixed mode refrigerant loop in compressed refrigerant mode and the second mixed mode refrigerant loop in pumped refrigerant mode; and   operating, as the cooling demand varies above the fourth demand level, both the first mixed mode refrigerant loop and the second mixed mode refrigerant loop in compressed refrigerant mode.   
     
     
         12 . The method of  claim 11 , wherein operating the first mixed mode refrigerant loop in pumped refrigerant mode comprises:
 circulating a working fluid through a first evaporator of the first mixed mode refrigerant loop and a heat exchanger; and   pumping a first refrigerant through a first condenser of the first mixed mode refrigerant loop and the first evaporator, thereby rejecting heat from the heat exchanger out of the first condenser.   
     
     
         13 . The method of  claim 12 , wherein isolating the second mixed mode refrigerant loop comprises trapping a portion of the working fluid in a second evaporator of the second mixed mode refrigerant loop and isolating the second evaporator from the heat exchanger. 
     
     
         14 . The method of  claim 11 , wherein operating both the first mixed mode refrigerant loop and the second mixed mode refrigerant loop in pumped refrigerant mode comprises
 circulating a working fluid through a first evaporator of the first mixed mode refrigerant loop, a second evaporator of the second mixed mode refrigerant loop, and a heat exchanger;   pumping a first refrigerant through a first condenser of the first mixed mode refrigerant loop and the first evaporator, thereby rejecting heat from the heat exchanger out of the first condenser; and   pumping a second refrigerant through a second condenser of the second mixed mode refrigerant loop and the second evaporator, thereby rejecting heat from the heat exchanger out of the second condenser.   
     
     
         15 . The method of  claim 11 , wherein operating the first mixed mode refrigerant loop in compressed refrigerant mode and the second mixed mode refrigerant loop in pumped refrigerant mode comprises
 circulating a working fluid through a first evaporator of the first mixed mode refrigerant loop, a second evaporator of the second mixed mode refrigerant loop, and a heat exchanger;   compressing a first refrigerant between the first evaporator and a first condenser of the first mixed mode refrigerant loop, thereby rejecting heat from the heat exchanger out of the first condenser; and   pumping a second refrigerant through a second condenser of the second mixed mode refrigerant loop and the second evaporator, thereby rejecting heat from the heat exchanger out of the second condenser.   
     
     
         16 . The method of  claim 11 , wherein operating both the first mixed mode refrigerant loop and the second mixed mode refrigerant loop in compressed refrigerant mode comprises
 circulating a working fluid through a first evaporator of the first mixed mode refrigerant loop, a second evaporator of the second mixed mode refrigerant loop, and a heat exchanger;   compressing a first refrigerant between the first evaporator and a first condenser of the first mixed mode refrigerant loop, thereby rejecting heat from the heat exchanger out of the first condenser; and   compressing a second refrigerant between the second evaporator and a second condenser of the second mixed mode refrigerant loop, thereby rejecting heat from the heat exchanger out of the second condenser.   
     
     
         17 . A mixed mode modular cooling system comprising:
 a first mixed mode refrigerant loop including a first evaporator, a first condenser, a first pump configured to selectively pump a first refrigerant through the first evaporator and the first condenser, and a first compressor configured to selectively compress the first refrigerant between the first evaporator and the first condenser;   a second mixed mode refrigerant loop including a second evaporator, a second condenser, a second pump configured to selectively pump a second refrigerant through the second evaporator and the second condenser, and a second compressor configured to selectively compress the second refrigerant between the second evaporator and the second condenser; and   plumbing configured to permit a working fluid to circulate through a heat exchanger, the first evaporator, and the second evaporator.   
     
     
         18 . The system of  claim 17 , wherein the plumbing further comprises:
 a first valve configured to selectively permit the working fluid to circulate through the first evaporator; and   a second valve configured to selectively permit the working fluid to circulate through the second evaporator.   
     
     
         19 . The system of  claim 17 , wherein the plumbing further comprises:
 a first output valve configured to selectively permit the working fluid to flow out of the first evaporator and selectively prevent the working fluid from flowing from the first evaporator; and   a second output valve configured to selectively permit the working fluid to flow out of the second evaporator and selectively prevent the working fluid from flowing from the second evaporator.   
     
     
         20 . The system of  claim 19 , wherein the plumbing further comprises:
 an input manifold disposed fluidically between the first and second evaporators, and the heat exchanger, respectively; and   an output manifold disposed fluidically between the first and second output valves, and the heat exchanger, respectively.