Numerical thermohydraulic investigation of developing mixed convective laminar flow through horizontal tubes with a uniform wall temperature

IF 4.9 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences Pub Date : 2025-04-23 DOI:10.1016/j.ijthermalsci.2025.109955

Deniél Steyn , Marilize Everts , Ken J. Craig

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Abstract

A numerical investigation of simultaneously developing laminar mixed convective flow in a horizontal tube under a uniform wall temperature (UWT) boundary condition was conducted. Two numerical models were created to examine the differences between experimental and numerical approaches. The first replicated an experimental UWT setup, while the second implemented an ideal UWT boundary condition. Simulations were performed in ANSYS Fluent with temperature-dependent water properties. The Reynolds number and Grashof number ranges were 500-2000 and 0.18×10³-9.43×10³, respectively. Length-to-diameter ratios varied between 1020 and 1632. The circulation strength of buoyancy-driven vortices was calculated to quantify free convection effects. Higher Grashof numbers intensified the circulation strength and shifted the peak circulation strength upstream. Increased Reynolds numbers delayed the occurrence of peak circulation strength without altering its magnitude. A boundary layer analysis indicated longer thermal and hydrodynamic entrance lengths with higher Grashof numbers or Reynolds numbers. Furthermore, the local Nusselt number decreased from a maximum at the tube inlet to a trough and then increased to a peak before declining to a value of 3.66. Elevated Grashof numbers amplified these trends and shifted the troughs and peaks upstream, whereas increasing Reynolds numbers delayed these extrema points without significantly affecting their magnitudes. Based on circulation strength and boundary layer behaviour, seven thermohydraulic regions were defined: (1) hydrodynamic-merge, (2) free convection increasing, (3) free convection dominating, (4) free convection settling, (5) sustained free convection, (6) hydrodynamically fully developed forced convective flow, and (7) thermally fully developed forced convective flow.

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均匀壁温水平管中发展混合对流层流的数值热水力研究

对等壁温度边界条件下水平管内同时发展的层流混合对流进行了数值研究。建立了两个数值模型来检验实验方法和数值方法之间的差异。第一个复制了一个实验性的UWT设置，而第二个实现了一个理想的UWT边界条件。在ANSYS Fluent中对温度相关的水性质进行了模拟。雷诺数范围为500 ~ 2000，Grashof数范围为0.18×103-9.43×103。长径比在1020到1632之间变化。通过计算由浮力驱动的涡旋的环流强度来量化自由对流效应。较高的Grashof数增强了环流强度，使峰值环流强度上移。雷诺数的增加延迟了循环强度峰值的出现，但不改变其大小。边界层分析表明，热流体动力入口长度越大，格拉什夫数或雷诺数越高。局部努塞尔数由管入口处的最大值先下降到波谷，再上升到峰值，最后下降到3.66。升高的Grashof数放大了这些趋势，使波谷和波峰向上游移动，而增加的雷诺数延迟了这些极值点，但不会显著影响它们的大小。根据环流强度和边界层特性，确定了7个热水力区：(1)流体动力合并区、(2)自由对流增强区、(3)自由对流主导区、(4)自由对流沉降区、(5)持续自由对流区、(6)流体动力充分发展的强迫对流区和(7)热动力充分发展的强迫对流区。

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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.