The effect of particle size on thermal and solute dispersion in saturated porous media
The effect of particle size on thermal and solute dispersion in saturated porous media
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DOI：
10.1016/j.ijthermalsci.2017.08.003
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发表时间：
2017-12
影响因子：
4.5
通讯作者：
Toshiyuki Bandai;S. Hamamoto;G. Rau;T. Komatsu;T. Nishimura
中科院分区：
文献类型：
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作者：
Toshiyuki Bandai;S. Hamamoto;G. Rau;T. Komatsu;T. Nishimura
饱和多孔介质中的对流传热受孔隙中流体速度和温度波动以及流体动力学混合对温度场的影响所引起的热弥散控制。虽然热分散系数，在热平衡模型（TEM）中的一个控制参数，已被调查的自然系统，热分散系数对颗粒尺寸的依赖性仍然是不确定的。以前的研究发现，热扩散系数和流速之间的关系遵循幂律，并且在固体和流体相之间可能存在温差（热非平衡）。然而，实验仅限于离散的颗粒尺寸，并且不同的实验方法阻碍了分散-速度关系的比较。我们进行了一系列单独的热量和溶质传输实验中填充的柱均匀多孔介质组成的不同尺寸的玻璃球的流速范围。从实验测量得到的热和溶质的分散系数与流速通过热或溶质的Péclet数。我们的研究结果表明，虽然溶质分散是独立的颗粒尺寸，基于TEM的热分散系数对流速的依赖性是由颗粒尺寸的影响。这是由以下事实引起的：与溶质输送不同，流体和颗粒之间进行热交换，并且这引起两相之间的热不平衡。由于没有考虑相之间的热不平衡，因此该结果对于定量天然多孔介质中的强迫对流热传输具有重要意义。在选择合适的热扩散系数值时，必须考虑多孔介质的颗粒尺寸。
Thermal dispersion, caused by fluid velocity and temperature fluctuations in the pore space and the effects of hydrodynamic mixing on the temperature field, controls convective heat transport in saturated porous media. While the thermal dispersion coefficient, a governing parameter in the thermal equilibrium model (TEM), has been investigated for natural systems, the dependence of the thermal dispersion coefficient on particle size remains undetermined. Previous research found that the relationship between the thermal dispersion coefficient and flow velocity follows a power law and that there may be a temperature difference between the solid and fluid phase (thermal non-equilibrium). However, experiments are limited to discrete particle sizes and comparison of the dispersion-velocity relationship is impeded by different experimental approaches. We conducted a series of separate heat and solute transport experiments in a column filled with uniform porous media consisting of different sized glass spheres for a range of flow velocities. The thermal and solute dispersion coefficients obtained from experimental measurements were correlated with flow velocities through the thermal or solute Péclet number. Our results demonstrate that, while solute dispersion is independent of particle size, the dependence of the TEM based thermal dispersion coefficient on flow rates is influenced by the particle size. This is caused by the fact that, unlike solute transport, heat exchanges between fluid and particles and that this induces thermal non-equilibrium between both phases. The results have significant implications for quantifying forced convective heat transport in natural porous media because thermal non-equilibrium between the phases is not considered. The porous media particle size must be considered when selecting appropriate values for the thermal dispersion coefficient.