Cooling system
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.