Heat transfer in a molten salt filled enclosure absorbing concentrated solar radiation
Heat transfer in a molten salt filled enclosure absorbing concentrated solar radiation
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吸收集中太阳辐射的熔盐填充外壳中的传热
DOI：
10.1016/j.ijheatmasstransfer.2017.04.028
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发表时间：
2017
影响因子：
5.2
通讯作者：
Amber I
中科院分区：
文献类型：
--
作者：
Amber I
本文对高径比（H/D）为0.5，1和2，瑞利数为107- 1011的高温熔盐封闭体直接吸收太阳辐射驱动的自然对流进行了数值模拟。感兴趣的域由刚性绝热垂直壁、有限厚度的导热底壁和开放的绝热顶面界定的流体腔组成，直接受到非均匀集中太阳能通量的照射。首先将盐体积加热，本文采用有限元法求解二维Navier-Stokes方程，该方程包含了与深度有关的体积热源和与温度有关的熔盐热物理过程，数值计算结果表明，熔盐的热物理过程与温度有关，而与温度有关的热物理过程与温度有关等温线和流线显示由明显的热毛细作用和浮力效应的不同层组成的非线性温度分布。低层流体流动发展随时间变化明显，表现为初始阶段、过渡阶段和准稳定阶段。自然对流的大小和每个阶段的持续时间被发现减少的纵横比从0.5增加到2。平均换热量的计算表明，Nusselt-Rayleigh数关系不是一致的线性关系，下边界面上的平均换热量随Ra的增大而增大。
Numerical simulations of the natural convection driven by the direct absorption of concentrated solar radiation by a high temperature molten salt filled enclosures for height to diameter ratios (H/D) of 0.5, 1 and 2 and Rayleigh numbers 107–1011is presented. The domain of interest consists of a fluid cavity bounded by rigid adiabatic vertical walls, a heat-conducting bottom wall of finite thickness and an open adiabatic top surface, directly irradiated by a non- uniform concentrated solar flux. The salt volume is first heated non-uniformly by direct absorption of solar radiation and subsequently from the lower absorber plate which is heated by the absorption of the radiation transmitted through the salt.A Finite Element Method is used to solve the time dependent two dimensional Navier Stokes equations that includes a depth dependent volumetric heat source and temperature dependent thermophysical of molten salts.Numerical results presented in terms of isotherms and streamlines show a nonlinear temperature profile consisting of distinct layers where thermocapilarity and buoyancy effects are evident. Fluid flow development in the lower layer is found to vary significantly with time and exhibits an initial stage, transitional stage and quasi-steady stages. The magnitude of the natural convection and the duration of each stage is found to decrease as the aspect ratio increases from 0.5 to 2. Calculation of the average heat transfer reveals that the Nusselt Rayleigh number relationship is not uniformly linear and the average heat transfer over the lower boundary surface increased with increasingRa.
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DOI：
--
发表时间：
1992
期刊：
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DOI：
--
发表时间：
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期刊：
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DOI：
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发表时间：
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期刊：
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