Numerical and experimental investigation of the heat transfer of spherical particles in a packed bed with an implicit 3D finite difference approach
Numerical and experimental investigation of the heat transfer of spherical particles in a packed bed with an implicit 3D finite difference approach
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DOI：
10.1007/s10035-017-0711-z
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发表时间：
2017-06
期刊：
影响因子：
2.4
通讯作者：
T. Oschmann;H. Kruggel-Emden
中科院分区：
文献类型：
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作者：
T. Oschmann;H. Kruggel-Emden
在周围流体存在下的填充床或流化床中的传热是与许多工业应用相关的重要现象。在这里，我们扩展了早期导出的3D传热模型（Oschmann等人，在Powder Technol 291：392-407，2016），以考虑毕奥数情况下的颗粒-流体热对流。离散元法（DEM），这是耦合与商业计算流体动力学（CFD）软件包ANSYS Fluent被用作建模框架。作为一个第一近似的流动引起的局部传热颗粒表面上的分布函数的不均匀性。为了验证解决的传热模型，我们比较DEM/CFD模拟三种不同的材料（木材，聚甲醛（POM）和铝）进行实验。这首先包括将颗粒表面温度与红外相机的测量结果进行比较的情况。其次，对颗粒核心和表面的平均床层温度进行了数值研究，以显示所使用的材料的差异。第三，核心温度的三个选定的粒子与实验进行比较。DEM/CFD框架提供了壁面效应可忽略的温度演变的准确描述。在靠近壁的地方，只有导热系数低的材料才能达到定性的一致。因此，在我们调查的第二部分中，我们提供了各种计算流体动力学模拟加热的氧化铝壁，这是需要的颗粒表面温度的红外摄像机测量的评估。模拟结果显示了与实验相同的趋势，强调了壁面处传热的复杂性，并且是在DEM/CFD框架的背景下制定复杂颗粒壁面传热模型的第一步。
Heat transfer in packed or fluidized beds in the presence of a surrounding fluid is an important phenomenon which is relevant to numerous industrial applications. Here we extend an earlier derived 3D heat transfer model (Oschmann et al. in Powder Technol 291:392–407, 2016) to take into account particle-fluid heat convection in the case of Biot numbers. The Discrete Element Method (DEM) which is coupled with the commercial Computational Fluid Dynamics (CFD) package ANSYS Fluent is used as the modelling framework. As a first approximation of the flow induced inhomogeneity of the local heat transfer on the particle surface a distribution function is employed. To validate the resolved heat transfer model, we compare DEM/CFD simulations of three different materials (wood, Polyoxymethylene (POM) and aluminum) with performed experiments. This firstly includes cases where particle surface temperatures are compared with measurements of an infrared camera. Secondly, a numerical study of the average bed temperatures of particle core and surface is conducted to show the differences of the used materials. Thirdly, the core temperatures of three selected particles are compared against experiments. The DEM/CFD framework provides an accurate description of the temperature evolution where the wall effects are negligible. Close to the walls a qualitative agreement can only be achieved for materials with low thermal conductivities. As a consequence of this, in the second part of our investigation we provide various CFD simulations for the heating of an aluminum oxide wall which is required for the evaluation of the particle surface temperatures measured by an infrared camera. The simulation results show the same tendencies as the experiments, underline the complexity of the heat transfer at the walls and are a first step for the formulation of a complex particle-wall heat transfer model in the context of a DEM/CFD framework.