Development Of Microclimate Cooling Systems For Increased Thermal Comfort Of Individuals

摘要

Miniature cooling systems have lately gained increased attention due to ever increasing needs to locally cool hot spots. Miniaturized cooling is needed in a variety of different applications, for example to cool powerful yet highly compact electronics or to increase the thermal comfort of individuals through man-mounted systems. This paper focuses on the development of components suitable to be used in miniaturized vapor compression systems. Of particular interest is the achievable cooling output to system mass ratio. Miniaturized aluminum microchannel heat exchangers, positive displacement compressors, and passive expansion devices have been designed, developed, and investigated both experimentally and numerically. Relevant performance data are presented and improvement potentials are revealed and assessed. A measured cooling capacity of 57 W at 35 oC and a system mass of 2.2 kg (including power source) yields, with 26 W kg-1 one of the highest cooling output to system mass ratios ever reported in the open literature available for miniature cooling technology. It is clear that vapor compression technology can outperform many other approaches, including cooling systems based on phase change materials with respect to cooling output per unit mass. Human subject system evaluations confirm the laboratory measurements. The tested system impressively demonstrates much slower increases of core body temperature and heart rate over time in humans experiencing high levels of physical activity in hot ambient conditions in comparison to the same test person exercising at identical activity levels, but without having a man-mounted cooling system.