Cooling apparatus and method

Abstract

Cooling apparatus providing two independent heat exchangers ( 18, 20 ) serially arranged with respect to a heat flow ( 42 ), each heat exchanger being connected to a respective independent chiller ( 32, 34 ). The apparatus incorporates an element of redundancy in order to effect an increase in operational efficiency, by being switchable between a first operation mode in which both chillers operate in a free cooling mode and a second operation mode in which a first chiller operates in a free cooling mode and a second chiller operates in a forced cooling mode.

1 . Apparatus for cooling heat flow from a heat source, the apparatus comprising:
 a first heat exchanger and a second heat exchanger arranged serially to receive the heat flow, the first heat exchanger being closer to the heat source than the second heat exchanger, each heat exchanger being connected to a respective coolant distribution circuit arranged to transfer coolant through its heat exchanger; and   a first chiller and a second chiller for cooling the coolant from the first and second heat exchangers respectively,   wherein the apparatus is switchable between:
 a first operation mode in which both the first and second chiller operate in a free cooling mode; and 
 a second operation mode in which the first operates in a free cooling mode and the second chiller operates in a forced cooling mode. 
   
     
     
         2 . Apparatus according to  claim 1 , in which the first and second chiller are both selectively operable in a free cooling mode or a forced cooling mode, and which is switchable to a third operation mode in which both the first and second chiller operate in the forced cooling mode. 
     
     
         3 . Apparatus according to  claim 2 , wherein the first and second chillers each include a compressor selectively connectable into the respective coolant distribution circuit. 
     
     
         4 . Apparatus according to  claim 3 , wherein each chiller includes a bypass circuit for diverting coolant past the compressor when operating in the free cooling mode. 
     
     
         5 . Apparatus according to  claim 1 , wherein the second chiller includes an auxiliary cooling circuit that is independent of the coolant distribution circuit connected to the second heat exchanger, the auxiliary cooling circuit conveying auxiliary coolant that is in thermal communication with the coolant distribution circuit connected to the second heat exchanger to cool the coolant in the coolant distribution circuit connected to the second heat exchanger. 
     
     
         6 . Apparatus according to  claim 5 , wherein a compressor is connected into the auxiliary cooling circuit when the second chiller operates in a forced cooling mode. 
     
     
         7 . Apparatus according to  claim 1  including a detector arranged to measure temperature or pressure of the coolant transferred out of the first heat exchanger, wherein the apparatus is arranged to switch to the second operation mode based on measurement made by the detector. 
     
     
         8 . Apparatus according to  claim 1 , wherein the heat exchangers are mounted on the door of a server rack. 
     
     
         9 . Apparatus according to  claim 1 , wherein the heat exchangers are evaporators. 
     
     
         10 . Apparatus according  claim 1 , wherein the coolant is liquid CO 2 . 
     
     
         11 . A server rack comprising:
 one or more servers mounted therein;   an air circulation unit arranged to direct a flow of air through the rack to draw heat away from the servers; and   apparatus according to  claim 1  arranged to cool the flow of air, wherein the heat source is the server(s) and the first and second heat exchangers are arranged serially to receive the flow of air, the first heat exchanger being closer to the servers than the second heat exchanger.   
     
     
         12 . A data centre comprising an enclosed space housing a plurality of server racks according to  claim 11 . 
     
     
         13 . Apparatus for cooling heat flow from a heat source, the apparatus comprising:
 a plurality of first heat exchangers and a plurality of second heat exchangers arranged as a plurality of first and second heat exchanger pairs serially mounted relative to respect to the heat flow, the first heat exchanger in each pair being closer to the heat source than the second heat exchanger;   a first common coolant distribution circuit connected to the plurality of first heat exchangers to transfer coolant therethrough;   a second common coolant distribution circuit connected to the plurality of second heat exchangers to transfer coolant therethrough; and   a first chiller arrangement and a second chiller arrangement for cooling the coolant output from the plurality of first heat exchangers and the plurality of second heat exchangers respectively,   wherein the apparatus is switchable between:
 a first operation mode in which both the first and second chiller arrangements operate in the free cooling mode; and 
 a second operation mode in which the first chiller arrangement operates in the free cooling mode and the second chiller arrangement operates in the forced cooling mode. 
   
     
     
         14 . Apparatus according to  claim 13 , in which both the first and second chiller arrangements are selectively operable in a free cooling mode or a forced cooling mode, and which is switchable to a third operation mode in which both the first and second chiller arrangements operate in the forced cooling mode. 
     
     
         15 . Apparatus according to  claim 13 , wherein each common coolant distribution circuit comprises a plurality of parallel cool outputs, each cool output being connected to deliver coolant to a respective heat exchanger on the circuit. 
     
     
         16 . Apparatus according to  claim 13 , wherein each common coolant distribution circuit comprises a common hot input connected to receive coolant from a plurality of heat exchangers on the circuit. 
     
     
         17 . Apparatus according to  claim 14 , wherein either or both of the first and second chiller arrangements comprise a plurality of chillers connected in parallel to the respective coolant distribution circuit, each chiller being selectively operable in a free cooling mode or a forced cooling mode. 
     
     
         18 . Apparatus according to  claim 13 , wherein the heat flow is a forced air current flowing from the heat source. 
     
     
         19 . A method of cooling heat flow from a heat source, the method comprising:
 delivering coolant independently to a first heat exchanger and a second heat exchanger from a first coolant transfer circuit and a second coolant transfer circuit respectively, the first and second heat exchangers being arranged serially to receive the heat flow, the first heat exchanger being closer to the heat source than the second heat exchanger;   measuring temperature or pressure of the coolant transferred out of the first heat exchanger; and   controlling the operation modes of a first chiller connected to the first coolant transfer circuit and a second chiller attached to the second coolant transfer circuit based on the measuring temperature or pressure,   wherein the method includes operating the first chiller in a free cooling mode and operating the second chiller in a forced cooling mode if the temperature or pressure of the coolant transferred out of the first heat exchanger exceeds a threshold.