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Micro heat exchangers, Micro-scale heat exchangers, or microstructured heat exchangers are heat exchangers in which (at least one) fluid flows in lateral confinements with typical dimensions below 1 mm. The most typical such confinement are microchannels, which are channels with a hydraulic diameter below 1 mm. Microchannel heat exchangers can be made from metal, ceramic,〔Kee, Robert J., et al. "The design, fabrication, and evaluation of a ceramic counter-flow microchannel heat exchanger." Applied Thermal Engineering 31.11 (2011): 2004-2012.〕 and even low-cost plastic.〔David C. Denkenberger, Michael J. Brandemuehl, Joshua M. Pearce, and John Zhai, (Expanded microchannel heat exchanger: design, fabrication and preliminary experimental test ), ''Proceedings of the Institution of Mechanical Engineers – Part A: Journal of Power and Energy'', 226, 532-544 (2012). DOI: 10.1177/0957650912442781〕 Microchannel heat exchangers can be used for many applications including: * high-performance aircraft gas turbine engines〔Northcutt, B., & Mudawar, I. (2012). Enhanced design of cross-flow microchannel heat exchanger module for high-performance aircraft gas turbine engines. Journal of Heat Transfer, 134(6), 061801.〕 * heat pumps〔Moallem, E., Padhmanabhan, S., Cremaschi, L., & Fisher, D. E. (2012). Experimental investigation of the surface temperature and water retention effects on the frosting performance of a compact microchannel heat exchanger for heat pump systems. international journal of refrigeration, 35(1), 171-186.〕 * air conditioning 〔Xu, B., Shi, J., Wang, Y., Chen, J., Li, F., & Li, D. (2014). Experimental Study of Fouling Performance of Air Conditioning System with Microchannel Heat Exchanger.〕 * heat recovery ventilators〔D. Denkenberger, M. Parisi, J.M. Pearce. ( Towards Low-Cost Microchannel Heat Exchangers: Vehicle Heat Recovery Ventilator Prototype ). ''Proceedings of the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics'' (HEFAT), 14–16 July 2014, Orlando, FL, USA.〕 ==Background== Investigation of microscale thermal devices is motivated by the single phase internal flow correlation for convective heat transfer: : Where is the heat transfer coefficient, is the Nusselt number, is the thermal conductivity of the fluid and is the hydraulic diameter of the channel or duct. In internal laminar flows, the Nusselt number becomes a constant. This is a result which can be arrived at analytically: For the case of a constant wall temperature, and for the case of constant heat flux .〔Incropera & Dewitt〕 As Reynolds number is proportional to hydraulic diameter, fluid flow in channels of small hydraulic diameter will predominantly be laminar in character. This correlation therefore indicates that the heat transfer coefficient increases as channel diameter decreases. Should the hydraulic diameter in forced convection be on the order of tens or hundreds of micrometres, an extremely high heat transfer coefficient should result. This hypothesis was initially investigated by Tuckerman and Pease. Their positive results led to further research ranging from classical investigations of single channel heat transfer〔Santiago, Kenny, Goodson, Zhang〕 to more applied investigations in parallel micro-channel and micro scale plate fin heat exchangers. Recent work in the field has focused on the potential of two-phase flows at the micro-scale.〔Mudawar〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Micro heat exchanger」の詳細全文を読む スポンサード リンク
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