Hybrid free cooling with condenser surface control

Abstract

A condenser includes valves allowing the total condensing surface of the condenser to be varied. The valves are controlled to maintain suitable pressure differentials in a mechanical cooling circuit while in a hybrid mode combining mechanical cooling by the mechanical cooling circuit with free cooling. Fan speeds for condenser/free cooling can be controlled in concert with the valves, allowing the fan speeds to be increased without causing the pressure differential to fall below requirements for operation of the mechanical cooling circuit.

1 . A condensing and free cooling system for a heating, ventilation, air conditioning, and refrigeration (HVACR) system, comprising:
 a working fluid inlet;   a first heat exchange portion including a first condensing surface;   a second heat exchange portion including a second condensing surface;   a working fluid outlet;   a valve configured to receive working fluid from the first heat exchange portion and selectively direct said received working fluid to at least one of the second heat exchange portion and the working fluid outlet;   one or more free cooling heat exchangers; and   a fan configured to direct an airflow over the at least one free cooling heat exchanger and at least one of the first condensing surface and the second condensing surface.   
     
     
         2 . The condensing and free cooling system of  claim 1 , further comprising a controller configured to receive a pressure differential of the HVACR system and to control the valve based on the pressure differential. 
     
     
         3 . The condensing and free cooling system of  claim 1 , further comprising a second fan configured to direct a second airflow over the second condensing surface and at least one of the one or more free cooling heat exchangers. 
     
     
         4 . The condensing and free cooling system of  claim 1 , further comprising a third heat exchange portion including a third condensing surface, and a second valve, wherein the second valve is configured to receive working fluid from the second heat exchange portion and selectively direct said received working fluid to at least one of the third heat exchange portion and the working fluid outlet. 
     
     
         5 . A heating, ventilation, air conditioning, and refrigeration (HVACR) system, comprising:
 a mechanical cooling circuit comprising:
 a compressor; 
 a condenser; 
 an expander; and 
 an evaporator; 
 wherein the condenser includes:
 a working fluid inlet; 
 a first heat exchange portion including a first condensing surface; 
 a second heat exchange portion including a second condensing surface; 
 a working fluid outlet; and 
 a valve configured to receive working fluid from the first heat exchange portion and selectively direct said received working fluid to at least one of the second heat exchange portion and the working fluid outlet; and 
 
   a process fluid circuit comprising one or more free cooling heat exchangers; and   one or more fans each configured to direct air over at least one of the first condensing surface and the second condensing surface and at least one of the one or more free cooling heat exchangers.   
     
     
         6 . The HVACR system of  claim 5 , further comprising a controller configured to operate one or more of the valve and the one or more fans based on a pressure differential in the mechanical cooling circuit. 
     
     
         7 . The HVACR system of  claim 6 , wherein the controller is configured to operate one or more of the valve and the one or more fans such that the pressure differential is maintained above an operational threshold of the mechanical cooling circuit. 
     
     
         8 . The HVACR system of  claim 5 , wherein the condenser further comprises a third heat exchange portion including a third condensing surface, and a second valve, wherein the second valve is configured to receive working fluid from the second heat exchange portion and selectively direct said received working fluid to at least one of the third heat exchange portion and the working fluid outlet. 
     
     
         9 . The HVACR system of  claim 5 , wherein the one or more free cooling heat exchangers includes at least a first free cooling heat exchanger and a second free cooling heat exchanger, and the one or more fans includes at least a first fan configured to direct a first airflow over the first condensing surface and the first free cooling heat exchanger, and a second fan configured to direct a second airflow over the second condensing surface and the second free cooling heat exchanger. 
     
     
         10 . A method of controlling a heating, ventilation, air conditioning, and refrigeration (HVACR) system, comprising:
 circulating a process fluid in a process fluid circuit, wherein the process fluid circuit includes one or more free cooling heat exchangers;   circulating a working fluid in a mechanical cooling circuit, wherein the mechanical cooling circuit includes a compressor and a condenser;   operating at least one fan so as to direct an airflow over at least one of the one or more free cooling heat exchangers and at least a portion of the condenser; and   controlling at least one valve of the condenser so as to allow or prevent flow of the working fluid from a first portion of the condenser to a second portion of the condenser, based on a pressure differential in the mechanical cooling circuit.   
     
     
         11 . The method of  claim 10 , wherein controlling the at least one valve reduces an effective condensing surface of the condenser when the pressure differential in the mechanical cooling circuit is at or below a threshold pressure differential value. 
     
     
         12 . The method of  claim 11 , wherein the threshold pressure differential value is a minimum pressure differential for operation of the compressor. 
     
     
         13 . The method of  claim 10 , wherein operating the at least one fan includes operating a first fan at a first speed and a second fan at a second speed, wherein the first fan directs a first airflow over at least one of the one or more free cooling heat exchangers and the first portion of the condenser when the first portion of the condenser has working fluid flowing therethrough, the second fan directs a second airflow over at least one of the one or more free cooling heat exchangers and the second portion of the condenser when flow of the working fluid to the second portion of the condenser is prevented by the valve, and wherein the second speed is greater than the first speed. 
     
     
         14 . The method of  claim 13 , wherein the first speed is determined based on the pressure differential in the mechanical cooling circuit. 
     
     
         15 . The method of  claim 13 , further comprising determining the second speed based on a desired outlet temperature of the one or more free cooling heat exchangers.