Extended heat sink design in server

A server comprising an array of heat generating processing units arranged in a front row and at least a rear row within a housing, each of the processing units in the array comprising a heat sink and a thermo siphon refrigeration circuit;

• the refrigeration circuit for each processing unit in the rear row comprising a first reservoir for refrigerant in an extended heat sink and a second reservoir for refrigerant in contact with each processing unit and at least one conduit for conveying vapor refrigerant from the second reservoir to the first reservoir, and a second conduit for conveying liquid refrigerant in the first reservoir to the second reservoir;
• and the refrigeration circuit for each processing unit in the front row comprising a third reservoir for refrigerant in a heat sink and a fourth reservoir for refrigerant in contact with each processing unit in the front row and at least one conduit for conveying vapor refrigerant from the fourth reservoir to the third reservoir, and a second conduit for conveying liquid refrigerant in the third reservoir to the fourth reservoir

A method of improving the heat transfer efficiency of a heat sink associated with heat generating electronic devices cooled by a single flow of cooling air, wherein the heat generating electronic devices are arranged in rows within a housing and each electronic device having its own heat sink, the method comprising elevating the heat sinks of the last row of electronic devices above the height of the heat sinks of the electronic devices in the first row.