The heart inspires a new cooling system

In August 2004, at the Micro Nano Breakthrough Conference in Portland, engineers from Oregon State University in the US, presented a new successful desorption system using branching microchannels. The system was inspired by the human blood pumping system, which uses a comparatively small pump - the heart - to move blood through great distances around the body (according to some estimates, through at least 60 000 miles of veins, arteries and capillaries). In the new cooling system, the same approach is being used: the large compressor traditionally used in the conventional cooling cycle is replaced by a small pump. This is done by eliminating the compression cycle and substituting an absorption cycle in which one of the major components is a desorber. Microchannel heat exchangers have been known to carry out part of the evaporation and condensation cycle, but high pressures are involved and there are often problems with flow maldistribution and vapour lock. Researchers discovered that branching the channels, as in the human circulatory system, works much better, and overcomes these problems. This enhances liquid movement without requiring high pressures. This technology is cited as a significant step towards the creation of a man-portable cooling system, which, due to its small size and light weight, may initially find uses, for example, in the military where the portable cooling unit would be carried by soldiers to pump coolant through a specially designed suit, preventing heat exhaustion when working in extremely hot climates. However, it could later be used in other applications such as automotive cooling and individualized heat pumps. The research is part of a 3-year, 5.2 million US dollar project supported by the US Department of Defense.