Flow Boiling Heat Transfer in Microchannel Heat Exchangers with Micro Porous Coating Surface

IF 1.5 4区 工程技术 Q3 ENGINEERING, MECHANICAL
Kuan-Fu Sung, I-Chuan Chang, Chien-Yuh Yang
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Abstract

This study experimentally investigated the heat transfer and pressure drop performance of refrigerant HFC-245fa flow boiling in microchannel heat exchangers with and without micro porous coating. The flow boiling heat transfer performance at various mass fluxes, heating rate, exit vapor qualities and surface coating thickness was compared. The test results show that the 52 m coating thickness porous surface exhibited 65% to 148% higher heat transfer performance than the smooth surface. However, for the 98 m microporous coating surface, the heat transfer coefficients were only from 41% to 90% higher than those on smooth surface at various mass fluxes. This shows that the thicker coating layer thickness did not provide better heat transfer performance. The improvement on the maximum heat fluxes by applying micro porous coatings was only 3% to 10% in comparing to that on smooth surface. Partial dryout was observed at high and moderate mass fluxes on both smooth and porous coating channels. It happened at lower exit vapor qualities in micro porous coating channels than that in smooth channels. The partial dryout exit vapor qualities increased with decreasing mass fluxes. For the lowest mass flux, owing to the low heat flux and low nucleation suppression, no significant partial dryout was investigated. The pressure drops in micro porous coating channels were around 25 to 47% higher than those in smooth channels. There was not significant influence of micro porous coating layer thickness on flow boiling pressures drops.
带微孔涂层表面的微通道热交换器中的流动沸腾传热
本研究通过实验研究了制冷剂 HFC-245fa 在有微孔涂层和无微孔涂层的微通道热交换器中流动沸腾的传热和压降性能。比较了不同质量通量、加热速率、出口蒸汽质量和表面涂层厚度下的流动沸腾传热性能。测试结果表明,涂层厚度为 52 m 的多孔表面的传热性能比光滑表面高 65% 至 148%。然而,对于 98 m 的微孔涂层表面,在不同的质量通量下,传热系数仅比光滑表面高出 41% 至 90%。这表明,较厚的涂层并不能提供更好的传热性能。与光滑表面相比,微孔涂层对最大热通量的改善仅为 3% 至 10%。在光滑和多孔涂层通道上,在高和中等质量流量时都会出现部分干化现象。与光滑通道相比,微孔涂层通道的出口蒸汽质量更低。随着质量通量的降低,部分干化的出口蒸汽质量也在增加。在最低质量通量下,由于热通量低和成核抑制率低,部分干化现象并不明显。微孔涂层层厚度对流动沸腾压降的影响不大。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Journal of Enhanced Heat Transfer
Journal of Enhanced Heat Transfer 工程技术-工程:机械
CiteScore
3.60
自引率
8.70%
发文量
51
审稿时长
12 months
期刊介绍: The Journal of Enhanced Heat Transfer will consider a wide range of scholarly papers related to the subject of "enhanced heat and mass transfer" in natural and forced convection of liquids and gases, boiling, condensation, radiative heat transfer. Areas of interest include: ■Specially configured surface geometries, electric or magnetic fields, and fluid additives - all aimed at enhancing heat transfer rates. Papers may include theoretical modeling, experimental techniques, experimental data, and/or application of enhanced heat transfer technology. ■The general topic of "high performance" heat transfer concepts or systems is also encouraged.
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