Combined chiller and free cooling system for operation at intermediate ambient temperature

Abstract

A system includes a first set of coils receive coolant from a first coolant line and provide the coolant to a second coolant line. A second set of coils receive coolant from a third coolant line and provide the coolant to a fourth coolant line. A first valve regulates flow of coolant between the first and third coolant line. A second valve regulates flow of coolant between the second and the fourth coolant lines. A third valve regulates flow of coolant between the fourth coolant line and a fifth coolant line coupled to a water evaporator and a three-way valve. The three-way valve regulates flow of coolant between the fifth coolant line, the third coolant line, and a coolant input line. A fourth valve regulates flow of coolant between the second coolant line and a water condenser. A controller adjusts the valves to operate in an intermediate temperature mode.

What is claimed is: 
     
         1 . A system comprising:
 a set of coils arranged in parallel, each coil configured to:
 receive coolant from a first coolant line 
 transfer heat from the received coolant to outdoor air; and 
 provide the coolant to a second coolant line; 
   wherein, for each pair of adjacent coils in the set of coils, the system comprises:
 a first valve positioned in the first coolant line between the pair of coils and configured to regulate flow of coolant in the first coolant line; and 
 a second valve positioned in the second coolant line between the pair of coils and configured to regulate flow of coolant in the second coolant line; and 
   a controller communicatively coupled to the first valve and the second valve for each pair of coils, the controller comprising a processor configured to:
 receive a temperature measurement and an indoor setpoint temperature; 
 determine, based on a comparison of the temperature measurement to the indoor setpoint temperature, a split operating mode in which to operate the system, wherein the determined split operating mode corresponds to operation of a first number of the set of coils in a refrigerant-based cooling mode and operation of a second number of the set of coils in a free cooling mode; 
 after determining the split operating mode in which to operate the system:
 cause the first valve to close in the first coolant line between a first pair of coils, such that the first number of the set of coils are in fluid communication with a water condenser operable for refrigerant-based cooling; and 
 cause the second valve to close in the second coolant line between the first pair of coils, such that the second number of the set of coils are in fluid communication with a coolant input of the system. 
 
   
     
     
         2 . The system of  claim 1 , wherein
 the temperature measurement is a measurement of an outdoor temperature; and   the processor is further configured to, prior to determining the split operating mode, determine that the system should operate in the split operating mode by:
 determining that the outdoor temperature is not greater than a threshold amount above the indoor setpoint temperature; and 
 determining that the outdoor temperature is not less than the threshold amount below the indoor setpoint temperature. 
   
     
     
         3 . The system of  claim 1 , wherein:
 the temperature measurement is a measurement of an outdoor temperature; and   the processor is further configured to determine the split operating mode by:
 comparing the indoor setpoint temperature and the outdoor temperature; 
 determining, based on the comparison of the indoor setpoint temperature and the outdoor temperature, the first number of coils to operate in the refrigerant-based cooling mode and the second number of the set of coils to operate in the free cooling mode. 
   
     
     
         4 . The system of  claim 3 , wherein the processor is further configured to:
 determine whether the outdoor temperature is within a first threshold range above a predefined temperature;   if the outdoor temperature is within the first threshold range above the predefined temperature, determine that the second number includes every coil except for one of the set of coils;   if the outdoor temperature is not within the first threshold range above the predefined temperature:
 determine that the outdoor temperature is within a second threshold range above the predefined temperature, wherein the second threshold range is larger than the first threshold range; and 
 determine that the second number includes every coil except for two of the set of coils. 
   
     
     
         5 . The system of  claim 1 , further comprising:
 a third valve positioned and configured to regulate flow of coolant from the second coolant line to an evaporator of the system;   a three-way valve positioned and configured to regulate flow of the coolant between the coolant input of the system, the evaporator, and the first coolant line; and   a fourth valve positioned and configured to regulate flow of the coolant between the water condenser and the first coolant line; and   wherein the processor is further configured to, after determining the split operating mode in which to operate the system:
 cause the third valve to be in an open position such that flow of the coolant is allowed between the fourth coolant line and the fifth coolant line; 
 cause the fourth valve to be in the open position such that flow of the coolant is allowed between the second coolant line and the water condenser; and 
 cause the three-way valve to be in a position such that flow of the coolant is: 
 allowed between the coolant input and first coolant line; and 
 prevented between the fifth coolant line and the evaporator. 
   
     
     
         6 . The system of  claim 5 , wherein:
 the temperature measurement is a measurement of a coolant temperature of coolant provided to the evaporator; and   the processor is further configured to, prior to determining the split operating mode, determine that the system should operate in the split operating mode by:
 determining that the coolant temperature is not greater than a threshold amount above the indoor setpoint temperature; and 
 determining that the coolant temperature is not less than the threshold amount below the indoor setpoint temperature. 
   
     
     
         7 . The system of  claim 1 , wherein the system further comprises:
 a coolant pump configured, when turned on, to provide a flow of coolant from the second coolant line to a water condenser; and   wherein the processor is further configured to cause the coolant pump to turn on.   
     
     
         8 . The system of  claim 1 , the system further comprising, for each coil of the first set of coils and the second set of coils, at least a corresponding fan.