Cooling system

Abstract

A closed circuit evaporative heat exchanger comprises an air distribution plenum ( 4 ), means ( 36 ) for spraying water into the plenum ( 4 ) and a collection surface ( 22 ) for collecting unevaporated water sprayed into the plenum ( 4 ). The water is arranged to drain into a sump ( 16 ) within the plenum ( 4 ) without remaining on the collection surface ( 22 ).

1 . A closed circuit evaporative heat exchanger comprising: 
 an air distribution plenum;    means for spraying water into said plenum;    a collection surface for collecting unevaporated water sprayed into said plenum, such that said water is arranged to drain into a sump within said plenum, substantially without remaining on the collection surface; and    a drain interface between the collection surface and the sump, said interface being arranged to form a liquid lock between the collection surface and the sump so that an uneven air pressure may be maintained between them;    wherein water within the sump is not exposed to airflow in the air distribution plenum.    
   
   
       2 . A heat exchanger as claimed in  claim 1  wherein said means for spraying water is arranged to operate with just sufficient water for said wet operation of the heat exchanger.  
   
   
       3 . A heat exchanger as claimed in  claim 2  arranged to operate with approximately 90 litres of water per square metre of coil area.