Abstract:
An electronic system includes an electronic device and a heat exchanger for exchanging heat with the device. The heat exchanger includes a flow duct for receiving a fluid, at least a portion of the flow duct being arranged in thermal communication with the device. The system further includes a pump associated with the flow duct and a Venturi tube for reducing the pressure of the fluid in the portion of the flow duct to a value less than the pressure external to the duct, to minimize any leakage of the fluid onto the device in the event the portion of the flow duct develops a leak.

Description:
REFERENCE TO RELATED APPLICATIONS 
     This application is a national stage application under 35 USC 371 of International Application No. PCT/GB2009/050956, filed Jul. 31, 2009, which claims the priority of United Kingdom Application No. 0819910.1, filed Oct. 30, 2008, the contents of which prior applications are incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The present invention relates to an electronic system and particularly, but not exclusively to a computer system. 
     BACKGROUND OF THE INVENTION 
     Computer systems, particularly so-called computer server units, generate significant heat during use and this heat must be removed to minimise damage to the associated components and provide for optimum component operation. The removal of heat is conventionally achieved by moving air over the components. The air is cooled at a remote location using heat exchangers to enable a temperature difference to be between the components and the air flowing thereover to be maintained. However, as the heat generated by such components increases in line with their ever increasing sophistication, together with the number of components and devices installed in any one location, the volume of air flow which must be passed through a server unit is correspondingly increased. Ultimately, the air flow becomes such that it may cause damage to or otherwise disrupt the components and must, therefore, be replaced by a more efficient cooling mechanism. 
     The removal of heat may be achieved by passing a liquid through a network of tubes in close proximity to the various components to extract the heat. However, if the tube becomes punctured or a joint between the tubes develops a leak, then the fluid will pass onto the associated components, which may thus further damage the server or computer. 
     The aforementioned disadvantages have been partially addressed in a known cooling system as illustrated in  FIG. 1 . Apparatus  10  is provided for cooling equipment  12  mounted on a framework  14 . A first reservoir  16  of coolant  18  is provided in the proximity of the framework  14 , a conduit  20  extends from reservoir  16  and describes a convoluted path over framework  14  to thereby enhance the surface area of conduit  20  that is in thermal communication with equipment  12 . The conduit  20  terminates at a second reservoir  22 , also configured to accommodate coolant  18 . An outlet of reservoir  22  feeds to a pump  24  via a conduit  26  to draw fluid from reservoir  22  which, in turn draws coolant through conduit  20 . Pump  24  also serves to return coolant to reservoir  16  via conduit  28 . 
     Pump  24  reduces the pressure of the coolant travelling through conduit  20  below atmospheric pressure. Consequently, if the conduit  20  is punctured or otherwise breached such that a potential leak path is formed therein, air is drawn into conduit  20  from the surrounding environment. A level of coolant in the second reservoir  22  drops as the air is drawn into the system  10 . Once this level passes below a lower level detection sensor  30  the pump  24  is switched off and gravity is used to feed coolant  18  into reservoir  22  until an upper level detection or sensor  32  senses an increase in coolant level within the second reservoir  22 . It follows that during this period of no pumping activity the pressure in the conduit  20  increases and there is a risk of coolant egress from the conduit  20  or that the framework  14  must be immediately isolated from the cooling system whilst the leak is repaired. 
     It is desirable to provide a cooling system that is able to continue operation of apparatus even if a leak of the aforementioned type is detected. We have now devised an electronic system which alleviates at least some of the above-mentioned problems. 
     SUMMARY OF THE INVENTION 
     According to a first aspect of the present invention, there is provided an electronic system, the system comprising:
         an electronic system, the system comprising:   an electronic device;   a heat exchanger for exchanging heat with the device, the heat exchanger comprising a flow duct for receiving a fluid, at least a portion of the flow duct being arranged for thermal communication with the device; and   means for reducing the pressure of the fluid in the portion of the flow duct to a value less than the pressure external to the duct, the pressure reducing means comprises:   a pump associated with the flow duct;   and a Venturi tube.       

     The reduced pressure of the fluid within the heat exchanger with respect to the pressure outside of the heat exchanger ensures that in the event of a leak or puncture in one of the flow ducts, for example tubes, of the heat exchanger, the fluid will not pass onto the components of the associated device. The reduced pressure thus ensures that the fluid is maintained within the tubes. Furthermore, by providing a Venturi tube in the pressure reducing means, the capacity of the system can readily be scaled up to control the thermal environment of an entire room of computational equipment without the need to provide additional local pumps. 
     The pump may be arranged within the flow duct. The fluid may comprise a liquid. 
     The internal cross-sectional area of the portion of the flow duct may be less than the internal cross-sectional area of a length of the flow duct, excluding said portion. 
     The portion of the flow duct may be arranged in thermal contact with those parts of the electronic device requiring the exchange of heat. 
     The electronic system may further comprise leak detection means for detecting a breach in the flow duct. The detection means may comprise sensing means for sensing the pressure of the fluid within the at least one flow duct. Alternatively, or in addition, the leak detection means may comprise ultrasonic sensing means for sensing the presence of air within the flow duct. 
     The system may further comprise alarm means for providing an alarm in response to signals output from the sensing means. The alarm means may be arranged to generate an alarm when the pressure sensing means senses a pressure value that is outside a range of pressure values. 
     The electronic device may comprise a computer or a computer server or a suite of computer servers e.g. a data room, each server may be mounted on a separate framework. Each framework may have a flow duct associated therewith, each respective flow duct being arranged in fluid communication with the pressure reducing means. 
     Preferably, the heat exchanger removes heat from the at least one device. 
     According to a second aspect of the present invention, there is provided a computer heat exchanger, the heat exchanger comprising:
         a flow duct for receiving a fluid, at least a portion of the flow duct being arranged in thermal communication with the device: and   means for reducing the pressure of the fluid in the portion of the flow duct to a value less than the pressure external to the duct, the pressure reducing means comprising:   a pump associated with the flow duct;   and a Venturi tube.       

    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the present invention will now be described by way of example only and with reference to the accompanying drawings, in which: 
         FIG. 1  is a schematic illustration of a conventional cooling system; 
         FIG. 2  is a schematic illustration of an electronic system according to a first embodiment of the present invention; and, 
         FIG. 3  is a schematic illustration of an electronic system according to a second embodiment of the present invention. 
         FIG. 4  is a schematic illustration of an electronic system according to a third embodiment of the present invention. 
         FIG. 5  is a schematic illustration of an electronic system according to a third embodiment of the present invention employing a suite of computer servers. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIG. 2  of the drawings, there is shown an electronic system  110  according to a first embodiment of the present invention. The system  110  comprises a plurality of computer components  111  and a heat exchanger  112  for removing the heat generated by the components ill during use of the computer (not shown). 
     The heat exchanger  112  comprises a fluid reservoir  113  for holding the fluid, for example a liquid  114 , and a circuit  15  through which the liquid  114  can flow. The circuit  115  comprises a primary flow duct  116  which extends from the base of the reservoir  113 , for example, along a first flow path before returning to the reservoir  113  at a position arranged near the surface of the liquid  114  within the reservoir  113 , for example. The primary flow duct  116  further comprises a Venturi tube  122 , arranged downstream of the pump  121  within the primary flow duct  116 , which comprises an inlet  122   a  and an outlet  122   b  connected by a narrow waist region  122   c . As the liquid  114  passes from the inlet  122   a  to the outlet  122   b  in moving along the primary flow duct  116 , it is necessary for the liquid  114  to move more quickly through the narrow waist region  122   c  than the inlet  122   a  and outlet  122   b , due to the conservation of mass. Accordingly, the pressure of the liquid  114  within this waist region  122   c  will become reduced with respect to the pressure of the liquid  114  within the primary flow duct  116 . 
     The circuit  115  further comprises a first secondary flow duct  123   a  which extends from the reservoir  113  at a position near the base of the reservoir  113 , for example. The first secondary flow duct  123   a  separates into a plurality of tertiary flow ducts  124   a - d , which pass in close proximity with the computer components  111  to facilitate the removal of the heat generated from the components during the operation of the computer (not shown). The tertiary flow ducts  124   a - d , subsequently combine with a second secondary flow duct  123   b , that is arranged in fluid communication with the waist region  122   c  of the Venturi tube  122 . 
     In use, the liquid  114  is pumped through the primary flow duct  116  along the first flow path by a pump  121  arranged within the primary flow duct  116 . The reduced pressure of the liquid  114  within the waist region  122   c  of the Venturi tube  122  and thus the second secondary flow duct  123   b , with respect to the liquid  114  within the reservoir, causes the liquid  114  to become drawn along a second flow path which is along the first secondary flow duct  123   a  and into the tertiary flow ducts  124   a - d . The tertiary flow ducts  124   a - d  may comprise a reduced diameter with respect to the secondary flow ducts  123  to maximise the surface area of the liquid for the efficient removal of heat from the components  111 . The pressure in the tertiary flow ducts  124   a - d  is, consequently sub atmospheric e.g. in the range of 0.6 to 0.8 bar abs, preferably in the range of 0.7 to 0.75 bar abs. 
     The liquid  114  subsequently passes into the second secondary flow duct  123   b  and into the waist  122   c  of the Venturi tube  122  before returning to the reservoir  113  via the outlet  122   b  of the Venturi tube  122 , along the primary flow duct  116 . The liquid  114  passing within the tertiary flow ducts  124   a - d  will become heated as the heat is extracted from the components  111 . This heated liquid will subsequently pass into the reservoir  113  where the heat can dissipate into the large volume of liquid  114  held therein. 
     In the event that one or more of the tertiary flow ducts  124   a - d  become punctured or if one or more of the seals (not shown) at the joints between the secondary  123   a - b  and tertiary flow ducts  124   a - d  become defective for example, the fluid surrounding the tertiary ducts  124   a - d , for example air, will become drawn into the respective duct through the puncture (not shown) or defective seal (not shown), rather than the liquid  114  escaping from the respective duct onto the computer components  111 . This will cause the pressure of the liquid  114  flowing along the second flow path to increase. This increase in pressure will be sensed by a pressure sensor  119  arranged within the tertiary flow duct  124   a - d . Each sensor  119  is arranged in communication with an alarm  120  such that when the sensor  119  detects a rise in pressure above a threshold value, the sensor  119  will output a signal to the alarm  120  to generate an alarm signal to warn an operator (not shown) for example, of the leak within the system  110 . Fewer sensors  119  than the number illustrated in  FIG. 2  may be provided e.g. a single sensor  119  may be provided in each tertiary flow duct  124   a - d  or a single sensor  119  may be located in an inflow secondary flow duct  123   a  and a second sensor  119  may be located in a return secondary flow duct  123   b.    
     Alternatively, or additionally a sensor  119 ′ may be provided in association with the secondary  123   a - b  and/or tertiary flow ducts  124   a - d . Sensor  119 ′ is an ultrasonic air detector, able to detect the presence of even small quantities of air that may be introduced into the flow ducts through a pinhole sized breach/puncture. Pressure sensor  119  may not be sufficiently sensitive to detect small leaks of this nature. 
     Operation of the electronic system  110  can proceed as normal until such a time that a planned maintenance event is scheduled when the breach can be repaired. In the meantime, little loss of cooling efficiently is experienced, and any such loss is local to the breach/puncture in the duct. Consequently, little or no disruption to the normal operation of the system  110  is experienced. 
     According to a second embodiment of the invention, as seen in  FIG. 3  of the drawings, there is shown an alternative electronic system  210  according to the present invention. The system  210  comprises a plurality of computer components  211  and a heat exchanger  212  for removing the heat generated by the components  211  during use of the computer (not shown). 
     The heat exchanger  212  comprises a fluid reservoir  213  for holding the fluid, for example a liquid  214 , and a circuit  215  through which the liquid  214  can flow. The circuit  215  comprises a first flow path along a primary flow duct  216  which extends from the base of the reservoir  213 , for example, before returning to the reservoir  213  at a position arranged near the surface of the liquid  213 , for example. The liquid  214  is pumped through the primary flow duct  216  along the first path by a pump  221  arranged within the primary flow duct  216 . The primary flow duct  216  further comprises a Venturi tube  222  positioned therein, downstream of the pump  221  and comprises an inlet  222   a  and an outlet  222   b  connected by a narrow waist region  222   c . As the liquid  214  passes from the inlet  222   a  to the outlet  222   b  in moving along the primary flow duct  216 , it is necessary for the liquid  214  to move more quickly through the narrow waist region  222   c  due to the conservation of mass and so the pressure of the liquid  214  within this waist region  222   c  will become reduced. At a position which lies within the primary flow duct  216 , intermediate the position of the pump  221  and Venturi tube  222 , there is provided a junction  225  to a first secondary flow duct  223   a , through which liquid  214  can flow along a second flow path. The first secondary flow duct  223   a  comprises a valve  226  which serves to enable the pressure of the liquid  214  exiting the valve  226  to be reduced compared with the pressure of the liquid  214  that is supplied to the valve  226 . Arranged downstream of the valve  226 , the first secondary flow duct  223   a  branches into a plurality of tertiary flow ducts  224   a - d  that pass in close proximity with the components  211  of a computer (not shown). The tertiary flow ducts  224   a - d  subsequently combine with a second secondary flow duct  223   b  that is in fluid communication with the waist  222   c  of the Venturi tube  222 . 
     The liquid  214  within the waist  222   c  of the Venturi tube  222  is at a reduced pressure compared with the pressure of the liquid  214  within the primary flow duct  216  and the section of the first secondary flow duct  223   a  arranged downstream of the valve  226 . As a result, this causes the liquid  214  to flow from the valve  226  through the tertiary flow ducts  224   a - d  into the waist  222   c  of the Venturi tube  222  via the second secondary flow duct  223   b . The liquid  214  subsequently exits the Venturi tube  222  via the outlet  222   b  and is returned to the reservoir  213  along the primary flow duct  216 . The liquid  214  passing within the tertiary flow ducts  224   a - d  will become heated as the heat is extracted from the components  211 . This heated liquid will subsequently pass into the reservoir  213  where the heat can dissipate into the large volume of liquid  214  held therein. 
     The liquid  214  flowing into the tertiary flow ducts  224   a - d  is at a reduced pressure compared with the pressure of the liquid  214  within the primary flow duct  216 . Accordingly, the pressure of the liquid within the tertiary flow ducts  224   a - d  becomes reduced to a level that is below the pressure of the fluid, for example air, that surrounds the tertiary flow ducts  224   a - d , e.g. approximately 0.7° bar abs. In the event that one or more of the tertiary flow ducts  224   a - d  becomes punctured or if one or more of the seals (not shown) at the joints between the secondary  223   a - b  and tertiary flow ducts  224   a - d  become defective for example, then the fluid surrounding the tertiary ducts  224   a - d  will become drawn into the ducts, rather than escaping onto the computer components  211 . This will cause the pressure within the ducts to increase, which will be sensed by a pressure sensor  219  arranged within the tertiary flow ducts  224   a - d . Each sensor  219  is arranged in communication with an alarm  220  such that when the sensor  219  detects a rise in pressure above a threshold value, the sensor  219  outputs a signal to the alarm  220  to generate an alarm signal to warn an operator (not shown) of the leak within the system  210 , similar to the first embodiment. Once again, fewer pressure sensors  219  than the number illustrated may be provided as described in relation to the first embodiment. One or more alternative, or additional, ultrasonic sensor  219 ′ may be provided in association with the secondary  223   a - b  and/or tertiary flow ducts  224   a - d  to detect small quantities of air present in the flow ducts. 
     From the foregoing exemplary embodiments therefore, it is evident that the reduced pressure of the liquid coolant within the heat exchanger associated with the electronic system of the present invention, minimises the transfer of the coolant onto the electronic components of the system in the event of a leak condition. 
     Whilst the embodiments depict a plurality of computer component  111 ,  211 , a single computer component can be cooled by a heat exchanger  112 ,  212  as herein described. However, a multitude of such components can also readily be cooled by such a heat exchanger  112 ,  212 . The capacity of the fluid reservoir  113 ,  213  and of the pumps  121 ,  221  can be increased and placed remotely from the system  110 ,  210  if necessary. A correspondingly higher capacity Venturi tube  122 ,  222  can be used to reduce the pressure of the cooling fluid to sub-atmospheric levels.