Impact Of A Ceramic Microchannel Heat Exchanger On A Micro Turbine


A highly effective recuperator with low-pressure drop is a key enabling technology to increase the efficiency of a micro turbine. To achieve a cycle efficiency above 40%, the average micro turbine would require a recuperator that achieves close to 99% effectiveness with a pressure drop as low as 2%. This paper presents the design and analysis of a microchannel heat exchanger that could be used as a recuperator in a micro turbine as an alternative to the currently used metallic primary surface recuperators that achieve an effectiveness of 90% at most. In the proposed design, the recuperator will be a counter flow, multi-layer design of parallel ducts with wall thickness of 50 μm and will be constructed with SiCN or a similar polymer derived ceramics, and fabricated using micro-stereolithography technology. Two designs, one having ducts with square cross-sections and the other with equilateral triangle cross-sections, are proposed and compared. For each design, the geometric parameters are optimized to provide the highest overall cycle efficiency while the volume of the heat exchanger is kept limited to 0.125 m3 and other cycle parameters are kept constant at typical values. For the square cross section design, the optimization process provides a design with an effectiveness of 0.961 and pressure loss of 2.86% that correspond to a cycle efficiency of 39.4%. The corresponding values for the triangle cross-section design are 0.983, 2.4% and 42.2%, respectively. Both designs are expected to withstand temperatures up to 1300°C in combustion gases. Special strategy is needed to fabricate any of these two microchannel designs by existing or proposed micro-stereolithography systems. One possible option is to make the complete heat exchanger as a bundle of identical smaller segments so that overall performance is not affected.

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American Society of Mechanical Engineers, International Gas Turbine Institute, Turbo Expo (Publication) IGTI



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Article; Proceedings Paper

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0036998015 (Scopus)

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