Next generation devices for electronic cooling with heat rejection to air

Conventional technology to cool desktop computers and servers is that of the direct heat removal heat sink, which consists of a heat sink/fan mounted on the CPU. Although this is a very cost effective solution, it is nearing its end of life. This is because future higher power CPUs will require a lower R-value than can be provided by this technology, within current size and fan limits. This paper discusses new technology that uses indirect heat removal technology, which involves use of a single or two-phase working fluid to transfer heat from the hot source to an ambient heat sink. This technology will support greater heat rejection than is possible with the direct heat removal method. Further, it will allow use of higher performance air-cooled ambient heat sinks than are possible with the direct heat removal heat sink. A concern of the indirect heat removal technology is the possibility that it may be orientation sensitive. This paper identifies preferred options and discusses the degree to which they are (or not) orientation sensitive. It should be possible to attain an R-value of 0.12 KIW at the balance point on the fan curve.