A numerical study of blockage and inclination effects on natural convection in a uniformly heated air flow channel

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL International Journal of Thermal Sciences Pub Date : 2025-02-13 DOI:10.1016/j.ijthermalsci.2025.109783

Siyu Ji, Quang Duy Nguyen, Yixiang Gan, Chengwang Lei

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Abstract

The present study is concerned with the flow behaviour and thermal performance of an air flow channel subject to uniform heating with an adiabatic circular cylinder symmetrically positioned in the channel. A two-dimensional numerical study is conducted, covering a range of blockage ratios (

β

, the ratio between the cylinder diameter to the channel width), inclination angles (

φ

, relative to horizontal plane), cylinder positions (

h

, the distance from the inlet), and Rayleigh numbers (

R a

, up to 6.0 × 10¹¹). It is observed that vortices shed from the cylinder interact with the thermal boundary layers (TBLs) adjacent to channel walls, which disturbs downstream TBLs and enhances mixing in the channel. For

R a

= 6.0 × 10¹¹, the averaged lateral wall temperature of a vertical channel (

φ

= 90°) drops by 31 % at

β

= 0.50, and the mass flow rate through the channel increases by 40 % at

β

= 0.25 compared to an unblocked vertical channel (i.e., without the cylinder). In a channel inclined at

φ

= 30°, up to 29 % reduction of the averaged wall temperature is achieved compared to an unblocked inclined channel at

R a

= 6.0 × 10¹¹. However, the inclination of the channel from the vertical position generally deteriorates its thermal performance. Moreover, at

β

= 0.75 and

R a

= 6.0 × 10¹¹, the flow skews towards one lateral wall at

φ

= 30° and 90°, resulting in an irregular wake, but the flow structures are more symmetric at

φ

= 60°. The results reported here provide a passive strategy to design obstacles in convective flow channels for optimising thermal performance.

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均匀加热气流通道中阻塞和倾斜对自然对流影响的数值研究

本研究是关于气流通道的流动行为和热性能受到均匀加热与绝热圆柱对称地放置在通道。进行了二维数值研究，包括堵塞比（β，柱体直径与通道宽度之比），倾角（φ，相对于水平面），柱体位置（h，与入口的距离）和瑞利数（Ra，高达6.0 × 1011）。观察到，从柱体脱落的涡与通道壁面附近的热边界层相互作用，扰动了下游热边界层，增强了通道内的混合。当Ra = 6.0 × 1011时，当β = 0.50时，垂直通道（φ = 90°）的平均侧壁温度下降了31%，而当β = 0.25时，通道的质量流量比未堵塞的垂直通道（即不加圆柱）增加了40%。在φ = 30°的倾斜通道中，与Ra = 6.0 × 1011的无堵塞倾斜通道相比，平均壁温降低了29%。然而，通道从垂直位置的倾斜通常会恶化其热性能。当β = 0.75和Ra = 6.0 × 1011时，在φ = 30°和90°处流动偏向一侧侧壁，形成不规则尾迹，但在φ = 60°处流动结构更为对称。本文报告的结果提供了一种被动策略来设计对流通道中的障碍物，以优化热性能。

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

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.