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首页> 外文期刊>International Journal of Heat and Mass Transfer >Calculation of the interfacial heat transfer coefficient in porous media employing numerical simulations
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Calculation of the interfacial heat transfer coefficient in porous media employing numerical simulations

机译：利用数值模拟计算多孔介质中的界面传热系数

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Numerical experiments in multiple representative elementary volumes (REVs) were conducted to validate calculations of macroscopic parameters for porous media models carried out employing a unit periodic cell (single REV). The simulation of a microscopic flow that develops through a porous medium formed by staggered square cylinders is presented to that purpose. A laminar steady flow regime is considered together with Peclet numbers in the 1-10~3 range and porosities between 55 and 95%. In particular, the interfacial heat transfer coefficient (h_(sf)) is analyzed by comparing results found in literature with those reported here. First, the outlet boundary condition that is generally employed in single REV simulations for the case of constant wall temperature was tested by comparing the values it imposes in the flow with those obtained far away from the outlet (unperturbed). It was found that this outlet boundary condition is adequate and moreover, that the flow rapidly develops to satisfy it (one or two REVs in simulated cases). Additionally, two definitions found in the literature to calculate the h_(sf) were compared, and it was shown that both calculations differ in approximately 20% for the 55% porosity case and still present significant differences (>5%) for greater porosities. The h_(sf) coefficient was also calculated as a function of the REV's positions in the porous structure to show that it is position dependent or, in other words, it shows pore scale fluctuations. Therefore, it is concluded that single REV simulations are, in general, not sufficient to compute the parameter. A double average that filters pore scale fluctuations was employed and differences between this quantity and those obtained in a single REV were quantified. The results show these differences are small (<2%) for Pe> 100 but differences can be up to 15% for Pe = 10 or larger, for lower Pe numbers. Finally, a method that allows capturing the pore scale fluctuation of the parameter by employing single REV values was proposed. This method can be employed to calculate the double average of the h_(sf) coefficient for other boundary conditions, or to calculate other macroscopic parameters, such as the thermal dispersion coefficients.
机译：进行了多个代表性基本体积（REV）的数值实验，以验证使用单元周期单元（单个REV）进行的多孔介质模型的宏观参数计算。为此目的，对通过交错的方形圆柱体形成的多孔介质中产生的微观流动进行了模拟。层流稳定流态与Peclet数在1-10〜3范围内，孔隙率在55％至95％之间一起考虑。特别是，通过将文献中发现的结果与此处报道的结果进行比较，来分析界面传热系数（h_（sf））。首先，通过将其施加在流中的值与远离出口（不受扰动）获得的值进行比较，来测试在恒定壁温的情况下通常在单个REV模拟中使用的出口边界条件。发现该出口边界条件是适当的，此外，流动迅速发展以满足该条件（在模拟情况下为一个或两个REV）。另外，比较了在文献中找到的用于计算h_（sf）的两个定义，结果表明，对于55％的孔隙率情况，两种计算方法的差异大约为20％，而对于更大的孔隙率，仍存在显着差异（> 5％）。还根据REV在多孔结构中位置的函数计算了h_（sf）系数，以表明它是位置相关的，换句话说，它显示了孔垢波动。因此，可以得出结论，一般而言，单次REV模拟不足以计算参数。使用过滤孔径变化的双重平均值，并量化此数量与单个REV中获得的数量之间的差异。结果表明，对于Pe> 100，这些差异很小（<2％），但对于Pe = 10或更高，对于Pe较低的数值，差异可以高达15％。最后，提出了一种方法，该方法允许通过使用单个REV值来捕获参数的孔尺度波动。该方法可用于计算其他边界条件的h_（sf）系数的两倍平均值，或计算其他宏观参数，例如热扩散系数。

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