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首页> 外文期刊>Journal of Heat Transfer >Heat Transfer Augmentation: Radiative-Convective Heat Transfer in a Tube With Fiber Array Inserts
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Heat Transfer Augmentation: Radiative-Convective Heat Transfer in a Tube With Fiber Array Inserts

机译：传热增强：具有纤维阵列插入物的管中的辐射对流传热

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摘要

Gas-phase heat transfer plays a critical role in many high temperature applications, such as preheaters, combustors, and other thermal equipment. In such cases common heat transfer augmentation methods rely on the convective component alone to achieve improved internal performance. Radiatively assisted heat transfer augmentation has been suggested as a way to overcome limitations in convective-only enhancement. One example of such a technique is the fiber array insert; thermal radiation emitted by tube walls is captured by a large number of slender fibers, which in turn convect heat to the flowing fluid. Previous numerical studies have indicated that this technique represents a promising enhancement method warranting further investigation. This paper presents results from an experimentally based feasibility study of fiber array inserts for heat transfer augmentation in an externally heated duct. Fibers composed of 140 fun silicon carbide and 150 μm stainless steel were assembled in arrays with porosities around 0.98, and were tested for empty-tube Reynolds numbers ranging from 17,500 to 112,500 and wall temperatures from ambient up to 750 ℃. The arrays cause a significant pressure drop-roughly two orders of magnitude higher than the empty-tube case-but tube-side heat transfer coefficients were improved by up to 100% over the convective-only case in the low flow rate regime. The stainless steel fiber array exhibited similar heat transfer performance as the silicon carbide case, although pressure drop characteristics differed owing to variations in fluid-structure flow phenomena. Pressure drop data were roughly within the range of d'Arcy law predictions for both arrays, and deviations could be explained by inhomogeneities in fiber-to-fiber spacing. Heat transfer was found to depend nonlinearly on wall temperature and flow rate, in contrast to previously reported numerical data.
机译：气相传热在许多高温应用中起着至关重要的作用，例如预热器，燃烧器和其他热力设备。在这种情况下，普通的传热增强方法仅依靠对流组件来实现改善的内部性能。有人建议采用辐射辅助传热来克服仅对流增强的局限性。这种技术的一个例子是光纤阵列插件。管壁发出的热辐射被大量细纤维捕获，这些细纤维又将热量对流到流动的流体中。先前的数值研究表明，该技术代表了一种有前途的增强方法，值得进一步研究。本文介绍了基于实验的纤维阵列插件在外部加热管道中增加传热的可行性研究结果。将由140有趣的碳化硅和150μm不锈钢组成的纤维组装成具有约0.98的孔隙率的阵列，并测试了空管雷诺数范围为17,500至112,500，壁温范围为环境温度高达750℃。阵列引起显着的压降-大约比空管情况高两个数量级，但在低流速条件下，仅对流情况下，管侧传热系数提高了100％。尽管由于流体结构流动现象的变化而使压降特性有所不同，但不锈钢纤维阵列仍具有与碳化硅外壳相似的传热性能。两种阵列的压降数据大致在d'Arcy定律的范围内，偏差可以用纤维间间距的不均匀性来解释。与先前报道的数值数据相反，发现热传递与壁温和流速非线性相关。

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