Chiller with setpoint adjustment

Abstract

A chiller system includes a compressor operable at a compressor speed between a first speed and a second speed to deliver a flow of compressed fluid to a manifold at a compressor pressure and a condenser in fluid communication with the manifold to receive the compressed fluid. A condenser fan is operable at a fan speed between a minimum fan speed and a maximum fan speed to direct a cooling flow to the condenser to cool the compressed fluid and an evaporator is positioned to receive the flow of compressed fluid and operable to cool a second fluid. A controller is operable at least partially in response to a measured temperature of the second fluid and a measured temperature of the cooling flow to determine a desired pressure and to vary the compressor speed and the fan speed such that the compressor pressure equals the desired pressure.

1 . A chiller system comprising:
 a compressor operable at a compressor speed between a first speed and a second speed to deliver a flow of compressed fluid to a manifold at a compressor pressure;   a condenser in fluid communication with the manifold to receive the compressed fluid;   a condenser fan operable at a fan speed between a minimum fan speed and a maximum fan speed to direct a cooling flow to the condenser to cool the compressed fluid;   an evaporator positioned to receive the flow of compressed fluid and operable to cool a second fluid; and   a controller operable at least partially in response to a measured temperature of the second fluid and a measured temperature of the cooling flow to determine a desired pressure and to vary the compressor speed and the fan speed such that the compressor pressure equals the desired pressure.   
     
     
         2 . The chiller of  claim 1 , wherein the compressor is a first of a plurality of compressors, each selectively operable at the compressor speed. 
     
     
         3 . The chiller of  claim 2 , wherein each of the compressors includes a centrifugal compressor. 
     
     
         4 . The chiller of  claim 1 , wherein the condenser includes a plurality of heat exchangers each arranged to receive a portion of the compressed fluid and to discharge the cooled compressed fluid to a condenser manifold. 
     
     
         5 . The chiller of  claim 4 , wherein the condenser fan is one of a plurality of fans, and wherein at least one fan is associated with each of the heat exchangers. 
     
     
         6 . The chiller of  claim 1 , further comprising a first sensor positioned to measure a property of the compressed fluid at the manifold. 
     
     
         7 . The chiller of  claim 6 , wherein the property is a pressure of the compressed fluid at the manifold. 
     
     
         8 . The chiller of  claim 7 , further comprising a second sensor positioned to measure the temperature of the cooling flow. 
     
     
         9 . The chiller of  claim 8 , further comprising a third sensor positioned to measure the temperature of the second fluid at a second fluid outlet. 
     
     
         10 . A chiller system comprising:
 a compressor operable at a compressor speed between a first speed and a second speed to deliver a flow of compressed fluid to a manifold;   a first sensor positioned to measure a property of the compressed fluid at the manifold;   a condenser in fluid communication with the manifold to receive the compressed fluid;   a condenser fan operable at a fan speed between a minimum fan speed and a maximum fan speed to direct ambient air flow to the condenser to cool the compressed fluid;   a second sensor positioned to measure the temperature of the ambient air flow;   an evaporator positioned to receive the flow of compressed fluid and operable to cool a second fluid and discharge the second fluid from an outlet;   a third sensor positioned to measure the temperature of the second fluid at the outlet; and   a controller in communication with the first sensor, the second sensor, and the third sensor and operable at least partially in response to the measured temperature of the second fluid and the measured temperature of the ambient air flow to determine a desired value and to vary the compressor speed and the fan speed such that the measured property equals the desired value.   
     
     
         11 . The chiller of  claim 10 , wherein the compressor is a first of a plurality of compressors, each selectively operable at the compressor speed. 
     
     
         12 . The chiller of  claim 11 , wherein each of the compressors includes a centrifugal compressor. 
     
     
         13 . The chiller of  claim 10 , wherein the condenser includes a plurality of heat exchangers each arranged to receive a portion of the compressed fluid and to discharge the cooled compressed fluid to a condenser manifold. 
     
     
         14 . The chiller of  claim 13 , wherein the condenser fan is one of a plurality of fans, and wherein at least one fan is associated with each of the heat exchangers. 
     
     
         15 . The chiller of  claim 10 , wherein the property is a pressure of the compressed fluid at the manifold. 
     
     
         16 . The chiller of  claim 10 , wherein the property is a temperature of the compressed fluid at the manifold. 
     
     
         17 . A method of controlling a chiller, the method comprising:
 operating a compressor at a compressor speed to discharge a compressed fluid at a compressor pressure;   directing the compressed fluid through a condenser;   operating a condenser fan at a fan speed to direct a cooling fluid toward the condenser to cool the compressed fluid in the condenser;   passing the compressed fluid through an expansion device to produce a flow of cool fluid;   passing the flow of cool fluid adjacent a second fluid to cool the second fluid;   measuring a temperature of the second fluid and a temperature of the cooling fluid;   calculating a desired compressor pressure at least partially in response to the measured temperature of the second fluid and the measured temperature of the cooling fluid;   varying the fan speed and the compressor speed so that the compressor pressure matches the desired compressor pressure.   
     
     
         18 . The method of  claim 17 , further comprising selectively operating each of a plurality of compressors at the compressor speed to discharge compressed fluid at the compressor pressure. 
     
     
         19 . The method of  claim 17 , further comprising dividing the compressed fluid into a plurality of paths, each path directing compressed fluid to one of a plurality of heat exchangers that cooperate to at least partially define the condenser.