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首页> 外文期刊>International Journal of Heat and Mass Transfer >On the evaluation of dryout conditions for a heat-releasing porous bed in a water pool
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On the evaluation of dryout conditions for a heat-releasing porous bed in a water pool

机译：关于水池中散热多孔床干燥条件的评估

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This work is motivated by the problem of restraining temperature escalation inside a porous heat releasing media submerged in a pool of liquid coolant. When coolant temperature reaches saturation, boiling begins in the bulk of the porous bed, with void generation rate determined by the heating power. Amount of void determines hydrostatic pressure difference that drives natural circulation of two-phase flow through the porous material. At a certain critical value of the heat release rate, the driving head cannot overcome drag of the two phase porous media flow, which results in complete evaporation of coolant in some zone. Temperature of material in the dry zone increases significantly due to deterioration of heat exchange with single phase vapor flow in comparison with boiling flow heat transfer. The paper considers the problem of determining the critical conditions for onset of dryout in a heat-releasing porous bed of an arbitrary shape. The well-known one-dimensional problem for a flat top-flooded bed is revisited, and the functional form of the dryout boundary (expressed as the dryout heat flux, DHF) is derived using non-dimensional parameters. Asymptotic behavior of the solution is analyzed, and, by the method of asymptotic interpolation, a surrogate model is proposed consisting of three single-argument, non-dimensional functions. It is shown that such a model provides acceptable accuracy even in the cases where complete similarity of solutions is not achieved. The results obtained provide important insights into the physics of the problem, reduce the number of free parameters, and enable fast evaluation of dryout conditions without the need of numerical solution of algebraic equations involved in the exact formulation. The ultimate goal of the surrogate model development, i.e. its application to multidimensional configurations, is discussed. (C) 2019 Elsevier Ltd. All rights reserved.
机译：这项工作是受抑制浸没在液体冷却剂池中的多孔散热介质内部温度升高问题的推动。当冷却剂温度达到饱和时，在多孔床的大部分中开始沸腾，空隙产生速率由加热功率决定。空隙量决定了驱动两相流通过多孔材料自然循环的静水压力差。在一定的放热率临界值下，驱动头无法克服两相多孔介质流的阻力，从而导致冷却剂在某些区域中完全蒸发。与沸腾传热相比，由于与单相蒸气流的热交换变差，干燥区中材料的温度显着升高。本文考虑了确定在任意形状的热释放多孔床中开始发生变干的临界条件的问题。再次讨论了平顶式流化床的一维问题，并使用无量纲参数推导了干燥边界的功能形式（表示为干燥热通量，DHF）。分析了该解的渐近行为，并通过渐近插值的方法，提出了由三个单参数无量纲函数组成的替代模型。结果表明，即使在解决方案没有完全相似的情况下，这种模型也可以提供可接受的精度。获得的结果为问题的物理性质提供了重要的见解，减少了自由参数的数量，并能够快速评估干燥条件，而无需对精确公式中涉及的代数方程式进行数值求解。讨论了替代模型开发的最终目标，即其在多维配置中的应用。 （C）2019 Elsevier Ltd.保留所有权利。

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