Abstract Heat transfer in granular flows plays an important role in particulate material processing such as food production, pharmaceuticals and biorenewable energy production. Better understanding of the thermodynamics in granular flows is essential for equipment design and product quality control. In this research, a particle-scale heat transfer model was developed within the frame of traditional Discrete Element Method (DEM), which considers both conductive heat transfer and radiative heat transfer among particles. A particle-wall heat transfer model was also proposed for resolving particle-wall conductive and radiative heat transfer. The developed thermal DEM model was validated by modeling heat transfer in packed beds and comparing simulation predictions with experimental measurements. The thermal DEM model was successfully applied to the simulation of heat transfer in binary component granular flows in a double screw reactor designed for biomass fast pyrolysis to gain better understanding of the heat transfer in the system. The existence of both spatial and temporal temperature oscillations is observed in the double screw reactor. The effects of the operating conditions on the average temperature profile, biomass particle temperature probability distribution, heat flux and heat transfer coefficient are analyzed. Results indicate that the particle-fluid-particle conductive heat transfer pathways are the dominant contributors to the total heat flux, which accounts for approximately 70%–80% in the total heat flux. Radiative heat transfer contributes 14%–26% to the total heat flux and the conductive heat transfer through contact surface takes only 1%–5% in the total heat flux. The total heat transfer coefficient in the double screw reactor is also reported, which varies from 70 to 110 W/(m2 ⋅K) depending on the operating conditions.

中文翻译：

---

双螺杆反应器中颗粒流传热的颗粒尺度模拟

摘要 颗粒流中的传热在颗粒材料加工中起着重要作用，例如食品生产、制药和生物可再生能源生产。更好地了解颗粒流中的热力学对于设备设计和产品质量控制至关重要。本研究在传统离散元法（DEM）的框架内开发了粒子尺度的传热模型，该模型同时考虑了粒子之间的传导传热和辐射传热。还提出了颗粒壁传热模型，用于解析颗粒壁传导和辐射传热。通过模拟填充床中的传热并将模拟预测与实验测量进行比较，验证了开发的热 DEM 模型。热 DEM 模型成功应用于模拟双螺杆反应器中二元组分颗粒流的传热，该反应器专为生物质快速热解而设计，以更好地了解系统中的传热。在双螺杆反应器中观察到时空温度波动的存在。分析了运行条件对平均温度分布、生物质颗粒温度概率分布、热通量和传热系数的影响。结果表明，颗粒-流体-颗粒传导传热途径是总热通量的主要贡献者，约占总热通量的70%~80%。辐射传热占总热通量的 14%~26%，接触面的传导传热仅占总热通量的 1%~5%。还报告了双螺杆反应器中的总传热系数，根据操作条件从 70 到 110 W/(m2·K) 不等。