A comprehensive understanding of heat transfer between the bed and immersed surfaces is critical for successfully designing and operating high-temperature gas–solid fluidized bed reactors. However, the impact of temperature on heat transfer, particularly in beds operating above 1000 °C, remains underexplored. This study investigates heat transfer between a fluidized bed and an immersed vertical surface over a temperature range of 300–1500 °C, with a focus on the relationship between heat transfer and bed hydrodynamics. The results indicate that below 1200 °C, the heat transfer coefficient (h₀) increases gradually with temperature, with radiative heat transfer contributing less than 18% to h₀. Above 1200 °C, h₀ exhibits an exponential increase for Al₂O₃ and ZrO₂ particles, while it decreases for MgO particles due to enhanced interparticle forces from particle softening and agglomeration. At 1500 °C, radiative heat transfer accounts for up to 30% of the total heat transfer. Additionally, smaller particles demonstrate higher h₀ but lower radiative contributions than larger particles. Increasing superficial gas velocity significantly reduces h₀ below 1200 °C but has minimal impact at higher temperatures. Larger beds reduce wall confinement effects, enhancing particle mixing and subsequently increasing h₀. A comparison of the experimental data with predictions from existing correlations reveals their inadequacy across the studied temperature range. To address this, a new empirical correlation is proposed to improve accuracy for predicting heat transfer in high-temperature fluidized beds.

中文翻译：

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了解传热和床体流体动力学在高温流化床中的作用


全面了解床层和浸没表面之间的传热对于成功设计和运行高温气固流化床反应器至关重要。然而，温度对传热的影响，特别是在 1000 °C 以上的床层中，仍未得到充分探索。本研究研究了流化床和浸没垂直表面在 300–1500 °C 温度范围内的传热，重点是传热与床流体动力学之间的关系。结果表明，在1200 °C以下，传热系数（h₀）随温度逐渐增加，辐射传热对h₀的贡献小于18%。在 1200 °C 以上，Al₂O₃ 和 ZrO₂ 颗粒的 h 0 呈指数级增加，而 MgO 颗粒的 h ₀ 则由于颗粒软化和团聚引起的颗粒间力增强而降低。在 1500 °C 时，辐射传热占总传热的 30%。此外，较小的粒子表现出较高的 h₀ 但比较大的粒子低的辐射贡献。增加表面气体速度会显著降低 h₀ 低于 1200 °C，但在较高温度下的影响最小。较大的床层减少了壁约束效应，增强了颗粒混合，从而增加了 h₀。将实验数据与现有相关性的预测进行比较，揭示了它们在研究温度范围内的不足。为了解决这个问题，提出了一种新的经验相关性，以提高预测高温流化床中传热的准确性。