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首页> 外文会议>ASME international conference on energy sustainability >EFFECTIVE THERMAL CONDUCTIVITY OF WALL-ADJACENT LAYER IN GRAVITY- DRIVEN VERTICAL DENSE GRANULAR FLOWS
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EFFECTIVE THERMAL CONDUCTIVITY OF WALL-ADJACENT LAYER IN GRAVITY- DRIVEN VERTICAL DENSE GRANULAR FLOWS

机译：重力驱动的垂直密实颗粒流中壁相邻层的有效热导率

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Particle-based heat transfer fluids for concentrated solar power (CSP) tower applications offer a unique advantage over traditional fluids as they have the potential to reach very high operating temperatures. Our work studies the heat transfer behavior of dense granular flows through cylindrical tubes as a potential system configuration for CSP towers. Thus far, we have experimentally investigated the heat transfer to such flows. Our results corroborate the observations of other researchers; namely, that the discrete nature of the flow limits the heat transferred from the tube wall to the flow due to an increased thermal resistance in the wall-adjacent layer. The present study focuses on this near-wall phenomenon, examining how it varies with system configuration and flow rate. A correlation to predict the thermal resistance, in the form of an effective thermal conductivity, was developed based on the underlying physics controlling the heat transfer. The model developed focuses on heat transfer via conduction, considering the heat transfer to particles in contact with the wall, heat transfer to particles not in contact with the wall, and heat transfer through the void spaces. Discrete Element Method simulations were used to examine the flow parameters necessary to understand the heat transfer in the wall-adjacent layer, in particular the packing fraction in the wall-adjacent layer and the number of particle-wall contacts. Incorporation of the model into the single-resistance model developed by Sullivan & Sabersky [1] showed good agreement with their experimental results and those of Natarajan & Hunt [2].
机译：用于聚光太阳能（CSP）塔式应用的基于颗粒的传热流体比传统流体具有独特的优势，因为它们有可能达到很高的工作温度。我们的工作研究了通过圆柱管的致密颗粒流的传热行为，将其作为CSP塔的潜在系统配置。到目前为止，我们已经通过实验研究了向此类流动的热传递。我们的结果证实了其他研究人员的观察;即，由于壁相邻层中的热阻增加，因此流动的离散性质限制了从管壁传递到流动的热量。本研究着眼于这种近壁现象，研究了它如何随系统配置和流速而变化。基于控制传热的基本物理原理，开发了以有效导热率形式预测热阻的相关性。开发的模型着重于通过传导的热传递，考虑到与壁接触的颗粒的热传递，与壁不接触的颗粒的热传递以及通过空隙的热传递。离散元方法模拟用于检查了解壁相邻层中的热传递所必需的流动参数，特别是壁相邻层中的填充分数和颗粒-壁接触的数量。将模型纳入Sullivan＆Sabersky [1]开发的单电阻模型中，与他们的实验结果以及Natarajan＆Hunt [2]的实验结果吻合良好。

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