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Inter-phase heat transfer and energy coupling in turbulent dispersed multiphase flows

机译：湍流分散多相流中的相间传热和能量耦合

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摘要

The present paper addresses important fundamental issues of inter-phase heat transfer and energy coupling in turbulent dispersed multiphase flows through scaling analysis. In typical point-particle or two-fluid approaches, the fluid motion and convective heat transfer at the particle scale are not resolved and the momentum and energy coupling between fluid and particles are provided by proper closure models. By examining the kinetic energy transfer due to the coupling forces from the macroscale to microscale fluid motion, closure models are obtained for the contributions of the coupling forces to the energy coupling. Due to the inviscid origin of the added-mass force, its contribution to the microscale kinetic energy does not contribute to dissipative transfer to fluid internal energy as was done by the quasi-steady force. Time scale analysis shows that when the particle is larger than a critical diameter, the diffusive-unsteady kernel decays at a time scale that is smaller than the Kolmogorov time scale. As a result, the computationally costly Basset-like integral form of diffusive-unsteady heat transfer can be simplified to a non-integral form. Conventionally, the fluid-to-particle volumetric heat capacity ratio is used to evaluate the relative importance of the unsteady heat transfer to the energy balance of the particles. Therefore, for gas-particle flows, where the fluid-to-particle volumetric heat capacity ratio is small, unsteady heat transfer is usually ignored. However, the present scaling analysis shows that for small fluid-to-particle volumetric heat capacity ratio, the importance of the unsteady heat transfer actually depends on the ratio between the particle size and the Kolmogorov scale. Furthermore, the particle mass loading multiplied by the heat capacity ratio is usually used to estimate the importance of the thermal two-way coupling effect. Through scaling argument, improved estimates are established for the energy coupling parameters of each energy exchange mechanism between the phases. (C) 2016 AIP Publishing LLC.
机译：本文通过尺度分析研究了湍流分散多相流中相间传热和能量耦合的重要基本问题。在典型的点粒子或双流体方法中，无法解决粒子尺度上的流体运动和对流传热，并且流体和粒子之间的动量和能量耦合由适当的封闭模型提供。通过检查由于从宏观尺度到微观尺度的流体运动的耦合力而产生的动能传递，获得了闭合模型，以求耦合力对能量耦合的贡献。由于附加质量力的来源不明显，它对微观动能的贡献不会像准稳态力那样有助于耗散地传递给流体内能。时标分析表明，当粒子大于临界直径时，扩散不稳定核的衰减时间小于Kolmogorov时标。结果，扩散-不稳定传热的计算上昂贵的类似于贝塞特的积分形式可以简化为非积分形式。常规地，使用流体与颗粒的体积热容比来评估不稳定的热传递对颗粒的能量平衡的相对重要性。因此，对于气体-颗粒流，其中流体与颗粒的体积热容比较小，通常会忽略不稳定的传热。但是，当前的结垢分析表明，对于较小的流体与颗粒体积的热容比，不稳定传热的重要性实际上取决于粒度与Kolmogorov结垢之间的比率。此外，通常用颗粒质量负荷乘以热容比来估算热双向耦合效应的重要性。通过比例论证，为相之间的每个能量交换机制的能量耦合参数建立了改进的估计。 （C）2016 AIP出版有限责任公司。

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