Also known as liquid submersion cooling, it is the practice of submerging computer components (or full servers) in a thermally, but not electrically, conductive liquid (dielectric coolant). Still rarely used for the cooling of IT Hardware, this method is slowly becoming popular with innovative datacenters the world over. IT Hardware or servers cooled in this manner don’t require fans and the heat exchange between the warm coolant and cool water circuit usually occurs through a heat exchanger (i.e. heater core or radiator). Some extreme density supercomputers such as the Cray-2 and Cray T90 use large liquid-to-chilled liquid heat exchangers for heat removal.