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首页> 外文期刊>International Journal of Heat and Mass Transfer >Modelling the Nu-Ra relationship to establish the intrinsic permeability of coarse open-graded materials from natural air convection tests in a 1 m~3 cell
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Modelling the Nu-Ra relationship to establish the intrinsic permeability of coarse open-graded materials from natural air convection tests in a 1 m~3 cell

机译：通过在1 m〜3单元中的自然空气对流测试中建立Nu-Ra关系模型以建立粗糙开放梯度材料的固有渗透率

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摘要

Natural air convection can substantially increase heat extraction rate from coarse open-graded granular materials. The initiation and extent of convection is strongly associated with the intrinsic permeability (K) of these materials. This paper presents a numerical study on natural air convection based on largescale laboratory experiments with a sample size of 1 m(3). The model allows modification of the existing analytical Nusselt (Nu) and Rayleigh (Ra) number relationship that was developed for a perfectly insulated and impervious cell with a square cross section. The Nu-Ra relationship derived from the numerical model accounts for the effect of side insulation, the presence of interface layers between the sample and temperature boundaries, and heat flux measurements that do not cover the entire horizontal surface. The model is based on a coupled heat and mass transfer with intra-pore convection, and was modeled using Darcy's law assuming linear flow conditions. The numerical model shows that the resulting Nu-Ra number relationship is dependent on the effective thermal conductivity (k(e)) of the sample. The final model is used to derive Nu-Ra number relationships for a k(e )ranging from 0.1 to 1.0 W/m degrees C. Heat transfer test results on very coarse open-graded materials are re-analysed with the developed Nu-Ra relationship to assess their intrinsic permeability. The procedure is applied to three crushed rock materials (20/120, 40/120 and 20/250 mm), natural cobbles (90/210 mm), and foam glass material (10/60 mm). The results show a varying degree of overestimation of the original K values based on the analytical Nu-Ra relationship compared to the K values based on the Nu-Ra relationship derived from the numerical model. The re-established K values are 16, 22 and 12% lower for the 20/120, 40/120 and 20/250 mm crushed rock material, respectively, 26% lower for natural cobbles, and 8% lower for foam glass material. Overall, the numerical model shows the importance of a test-setup- and material-specific Nu-Ra relationship for more precise establishment of K values. (C) 2019 Elsevier Ltd. All rights reserved.
机译：自然空气对流可以显着提高从粗糙的开放级粒状材料中提取的热量。对流的开始和程度与这些材料的固有渗透率（K）密切相关。本文基于大型实验室实验，对自然空气对流进行了数值研究，样本大小为1 m（3）。该模型允许修改现有的解析Nusselt（Nu）和Rayleigh（Ra）数关系，该关系是为具有方形横截面的完全绝缘和不渗透的单元而开发的。从数值模型得出的Nu-Ra关系说明了侧面绝缘的影响，样品和温度边界之间存在界面层以及未覆盖整个水平表面的热通量测量结果。该模型基于具有孔内对流的传热和传质耦合，并在假定线性流动条件的情况下使用达西定律建模。数值模型表明，所得的Nu-Ra数关系取决于样品的有效热导率（k（e））。最终模型用于推导ak（e）的Nu-Ra数关系，范围从0.1到1.0 W / m摄氏度。利用已开发的Nu-Ra关系，重新分析了非常粗糙的开放级材料的传热测试结果。评估其固有渗透率。该程序应用于三种碎石材料（20 / 120、40 / 120和20/250 mm），天然鹅卵石（90/210 mm）和泡沫玻璃材料（10/60 mm）。结果表明，与基于数值模型得出的基于Nu-Ra关系的K值相比，基于分析Nu-Ra关系的原始K值有不同程度的高估。对于20 / 120、40 / 120和20/250 mm碎石材料，重新建立的K值分别降低16、22和12％，对于天然鹅卵石，其K值降低26％，对于泡沫玻璃材料，其K值降低8％。总的来说，数值模型显示了测试设置和材料特定的Nu-Ra关系对于更精确地确定K值的重要性。 （C）2019 Elsevier Ltd.保留所有权利。

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    Rieksts Karlis; Hoff Inge; Scibilia Elena; Cote Jean;

  • 作者单位

    Norwegian Univ Sci & Technol, Dept Civil & Environm Engn, Hogskoleringen 7A, N-7491 Trondheim, Norway;

    Norwegian Univ Sci & Technol, Hogskoleringen 7A, N-7491 Trondheim, Norway;

    Norwegian Univ Sci & Technol, Hogskoleringen 7A, N-7491 Trondheim, Norway;

    Laval Univ, Dept Civil & Water Engn, Pavillon Adrien Pouliot,1065 Ave Med, Quebec City, PQ G1V 0A6, Canada;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);
  • 原文格式 PDF
  • 正文语种 eng
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