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首页> 外文期刊>International Journal of Heat and Mass Transfer >Heat transfer characteristics in a pressurized fluidized bed of fine particles with immersed horizontal tube bundle
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Heat transfer characteristics in a pressurized fluidized bed of fine particles with immersed horizontal tube bundle

机译：水平管束浸没在细颗粒加压流化床中的传热特性

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摘要

The effect of pressure on the average and local heat transfer coefficients between a submerged horizontal tube (25.4 mm-O.D.) and a fluidized bed has been determined in a fluidized-bed-heat-exchanger (FBHE; 0.20 × 0.26 × 0.58 m-high) of silica sand particles. The heat transfer coefficients were measured around the tube circumference by thermocouples. The average heat transfer coefficient (h_(avg)) exhibits a maximum value with variation of gas velocity (U_g) irrespective of pressure. The h_(avg) increases with increasing pressure at a given fluidizing number (U_g/U_(mf)) due to increase of gas density and improvement of fluid-izing quality with indication of low standard deviation of solid holdup fluctuation. Variation of instantaneous local heat transfer coefficient (h_i) is a function of bubble behavior around the tube surface. The h, exhibits higher values at the bottom than top location of the tube, and the highest value at the side of the tube (0°) at the given bed pressure. Instantanous h_i variations at the top regions (+45°, +90°) becomes much uniform with high peak frequency at higher pressures. The obtained maximum heat transfer coefficients (h_(max)) in terms of the maximum Nusselt numbers (Nu_(max)) have been correlated with Archimedes, Prandtl and Froude numbers.
机译：已在流化床热交换器（FBHE；高0.20×0.26×0.58 m）中确定了压力对浸没式水平管（外径25.4 mm）和流化床之间平均和局部传热系数的影响。 ）的硅砂颗粒。传热系数是通过热电偶在管周围测量的。平均传热系数（h_（avg））随压力（U_g）的变化而呈现最大值。在给定的流化数（U_g / U_（mf））下，h_（avg）随着压力的增加而增加，这归因于气体密度的增加和流化质量的改善，并表明固体滞留量波动的标准差较低。瞬时局部传热系数（h_i）的变化是管表面周围气泡行为的函数。在给定的床压下，h在管的底部比顶部的位置显示更高的值，在管的侧面（0°）显示最大值。顶部区域（+ 45°，+ 90°）处的瞬时h_i变化在较高压力下具有较高的峰值频率，变得非常均匀。获得的最大努塞尔特数（Nu_（max））的最大传热系数（h_（max））已与阿基米德，普朗特和弗洛德数相关。

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