The vortex-driven heat transfer coefficient of the inner surface of the inclined cylindrical holes under the influence of the length-to-diameter ratio

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences Pub Date : 2025-09-23 DOI:10.1016/j.ijthermalsci.2025.110328

Fangfang Wu , Lin Ye , Cunliang Liu , Mengnan Fan , Jingyin Shi

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引用次数: 0

Abstract

As a critical element of active cooling technology, the internal flow within film holes exhibits three-dimensional flow characteristics due to factors such as geometric configuration, wall effects, shear forces, velocity gradients, and pressure gradients. These complex flow behaviors significantly influence the distribution of the Nusselt number. In this study, thermochromic liquid crystal experiments were conducted to investigate the internal heat transfer characteristics of film holes, while numerical simulations were used to analyze the internal flow structures. The effects of Reynolds number, length-to-diameter ratio, and hole inclination angle were systematically explored, and incorporated as correction factors into conventional internal heat transfer correlations. The results indicated that the internal flow is dominated by a complex three-dimensional vortex system consisting of inlet separation vortices, shear layer vortices, and secondary counter-rotating vortices. Driven by these vortices, the streamwise Nusselt number distribution exhibits a rise-and-fall trend, with the peak appearing in the 0-1D entrance region, where the Nusselt number is approximately three times higher than in the fully developed region. Increasing the length-to-diameter ratio does not change the overall Nusselt number distribution pattern but enhances the extent of flow development, with full development occurring after about 5D. In contrast, variations in hole inclination angle introduce varying degrees of inlet effects.

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长径比对斜圆柱孔内表面涡动换热系数的影响

作为主动冷却技术的关键要素，膜孔内部流动受几何构型、壁面效应、剪切力、速度梯度和压力梯度等因素的影响，呈现出三维流动特征。这些复杂的流动行为显著地影响了努塞尔数的分布。本研究通过热致变色液晶实验研究膜孔内部换热特性，并通过数值模拟分析膜孔内部流动结构。系统地探讨了雷诺数、长径比和孔倾角的影响，并将其作为校正因子纳入常规内部传热相关性中。结果表明，内部流动是由入口分离涡、剪切层涡和二次反旋涡组成的复杂三维涡系统主导的。在这些涡的驱动下，努塞尔数的沿流分布呈现出上升和下降的趋势，峰值出现在0-1D入口区域，该区域的努塞尔数大约是完全发达区域的3倍。增加长径比不会改变整体努塞尔数分布格局，但会增强流动发育程度，在5D左右出现完全发育。相反，孔倾角的变化会带来不同程度的进口效应。

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来源期刊

International Journal of Thermal Sciences 工程技术-工程：机械

CiteScore

8.10

自引率

11.10%

发文量

531

审稿时长

55 days

期刊介绍： The International Journal of Thermal Sciences is a journal devoted to the publication of fundamental studies on the physics of transfer processes in general, with an emphasis on thermal aspects and also applied research on various processes, energy systems and the environment. Articles are published in English and French, and are subject to peer review. The fundamental subjects considered within the scope of the journal are: * Heat and relevant mass transfer at all scales (nano, micro and macro) and in all types of material (heterogeneous, composites, biological,...) and fluid flow * Forced, natural or mixed convection in reactive or non-reactive media * Single or multi–phase fluid flow with or without phase change * Near–and far–field radiative heat transfer * Combined modes of heat transfer in complex systems (for example, plasmas, biological, geological,...) * Multiscale modelling The applied research topics include: * Heat exchangers, heat pipes, cooling processes * Transport phenomena taking place in industrial processes (chemical, food and agricultural, metallurgical, space and aeronautical, automobile industries) * Nano–and micro–technology for energy, space, biosystems and devices * Heat transport analysis in advanced systems * Impact of energy–related processes on environment, and emerging energy systems The study of thermophysical properties of materials and fluids, thermal measurement techniques, inverse methods, and the developments of experimental methods are within the scope of the International Journal of Thermal Sciences which also covers the modelling, and numerical methods applied to thermal transfer.