A method of maintaining a server rack within a predetermined temperature range, including the removal of heat from the server rack by both conductive and convective heat transfer. Thermal contact structure is placed between the server rack and a heat sink. The heat sink may be in the form of a housing containing a radiator in one wall, and a bank of fans in an opposite wall to draw a coolant gas through the radiator. The coolant gas contacts the heat sink and a portion of the coolant gas is directed towards the server rack. Cooling liquid is supplied to the radiator by a chiller, which can be adjacent to the heat sink or located remotely from the heat sink.