首页> 外文期刊>International Journal of Heat and Mass Transfer >Determination of the interfacial heat transfer coefficient between forced air and sand at Reynold's numbers relevant to smouldering combustion
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Determination of the interfacial heat transfer coefficient between forced air and sand at Reynold's numbers relevant to smouldering combustion

机译:用与阴燃有关的雷诺数确定强迫空气和沙子之间的界面传热系数

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摘要

Heat transfer between flowing air and a fixed sand bed at low Reynold's number (i.e., Re < 30) is central to numerous natural and applied processes, including smouldering combustion. The most widely used correlation for the heat transfer coefficient (h_(sg)) predicts Nusselt numbers so high, it effectively presumes local thermal equilibrium for these systems; an assumption that has never been tested. In this work, twelve column experiments combined with numerical modelling quantify h_(sg) across a range of relevant sand grain sizes (0.125 < d_p < 2.000 mm) and air flow rates (0.5 < Re < 31). All of the sand properties were determined independently, with only h_(sg) determined via inverse modelling. A new empirical correlation for h_(sg) is obtained, Nu = 0.001 (Re~(1.97) Pr~(1/3)), which is then validated against two additional experiments. A newly developed criterion for assuming local thermal equilibrium is shown to be violated in all of these convection-dominated experiments and the extent of non-equilibrium between sand and air is quantified. The centerline temperatures are demonstrated to be sensitive not only to h_(sg) but also to a global heat loss coefficient quantified from the experiments in a novel manner. Overall, the new h_(sg) correlation is demonstrated to be reliable for predicting the interphase heat transfer in these systems and its application is expected to be valuable for a wide range of processes including smouldering.
机译:雷诺数较低(即Re <30)的流动空气与固定沙床之间的热传递是许多自然和应用过程(包括阴燃)的核心。传热系数(h_(sg))使用最广泛的相关性可以预测Nusselt数值如此之高,从而有效地假定了这些系统的局部热平衡。从未经过检验的假设。在这项工作中,十二个柱实验与数值模型相结合,在一系列相关的沙粒尺寸(0.125

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