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首页> 外文期刊>International Journal of Heat and Mass Transfer >Numerical investigation of transient natural convection in a vertical channel-chimney system symmetrically heated at uniform heat flux
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Numerical investigation of transient natural convection in a vertical channel-chimney system symmetrically heated at uniform heat flux

机译：均匀热流对称加热的垂直通道-烟囱系统瞬态自然对流的数值研究

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摘要

In the present numerical investigation, a transient numerical analysis for natural convection in air, between two vertical parallel plates (channel), heated at uniform heat flux, with adiabatic parallel plates downstream (chimney), is carried out by means of the finite volume method. The analyzed transient problem is two-dimensional and laminar. The computational domain is made up of the channel-chimney system, and two reservoirs, placed upstream the channel and downstream the chimney. The reservoirs are important because they simulate the thermal and fluid dynamic behaviors far away from the inflow and outflow regions. Results are presented in terms of wall temperature and air velocity profiles. They are given at different Rayleigh number and expansion ratios (chimney gap/channel gap) for a fixed channel aspect ratio (channel height/channel gap) equal to 10 and extension ratio (channel-chimney height/chan nel height) equal to 2.0. Wall temperature profiles over a period show the presence of overshoots and undershoots. The comparison among the maximum wall temperatures shows that the simple channel is the most critical configuration at steady state condition, but it is the best configuration during the tran sient heating at the first overshoot. As indicated by the temperature profiles, average Nusselt number profiles over a period of consideration show minimum and maximum values and oscillations before the steady state. Stream function fields allow to observe the development of fluid dynamic structures inside the channel-chimney system, particularly how and when the cold inflow is present and develops.
机译：在目前的数值研究中，通过有限体积法对两个垂直平行板（通道）之间以均匀热通量加热的空气中自然对流进行了瞬态数值分析，而绝热平行板位于下游（烟囱）。 。分析的瞬态问题是二维和层流的。计算域由通道烟囱系统和两个储层组成，两个储层分别位于通道上游和烟囱下游。储层之所以重要，是因为它们模拟了远离流入和流出区域的热和流体动力学行为。结果以壁温和空气流速曲线表示。对于固定的通道长宽比（通道高度/通道间隙）等于10，而扩展比（通道-烟囱高度/通道高度）等于2.0，则以不同的瑞利数和扩展率（烟囱间隙/通道间隙）给出它们。一段时间内的壁温曲线表明存在过冲和下冲。最高壁温之间的比较表明，在稳态条件下，简单通道是最关键的配置，但在第一次超调时的瞬态加热期间，它是最佳配置。如温度曲线所示，在考虑的时间段内，平均Nusselt数曲线显示出稳态之前的最小值和最大值以及振荡。流函数域允许观察通道烟囱系统内部流体动力结构的发展，特别是如何以及何时出现和发展冷流。

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