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

机译：水平管束沉浸在流化床中的传热和气泡特性

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摘要

The effect of gas velocity on the average and local heat transfer coefficients between a submerged horizontal tube (25.4 mm-OD) and a fluidized bed has been determined in a fluidized-bed-heat-exchanger (0.34 x 0.50 x 0.6 m-high) of silica sand particles. The heat transfer coefficients and the properties of bubble and emulsion phases were simultaneously measured at the same location around the tube circumference by thermocouples and an optical probe. The average heat transfer coefficient (h_(avg)) exhibits a maximum value with variation of gas velocity (U_g). The local heat transfer coefficient (h_i) exhibits maximum values at the side of the tube (0°) Bubble frequency (f_b) increases and the emulsion contacting time (t_e) decreases with increasing U_g. The h_i increases with increasing f_b and decreasing t_e. The f_b, exhibits higher values and t_e is shorter at the bottom (under each side) than those at the top section of the tube. The t_e and bubble fraction (δ_b) have been correlated with Froude number. The predicted h_(avg) values of small particles based on the packet renewal model and the emulsion contacting characteristics around the tube well accord to the experimental data.
机译：在流化床换热器（0.34 x 0.50 x 0.6 m高）中确定了气体速度对浸没式水平管（25.4 mm-OD）和流化床之间平均和局部传热系数的影响。硅砂颗粒。通过热电偶和光学探头在管圆周周围的同一位置同时测量了传热系数以及气泡和乳液相的性质。平均传热系数（h_（avg））随气体速度（U_g）的变化而呈现最大值。局部传热系数（h_i）在管子的侧面（0°）呈现最大值。气泡频率（f_b）增大，乳剂接触时间（t_e）随着U_g增大而减小。 h_i随着f_b的增加和t_e的减少而增加。 f_b具有较高的值，而t_e在底部（在每侧下方）比在管的顶部短。 t_e和气泡分数（δ_b）已与Froude数相关。基于小包更新模型和管子周围乳液接触特性的小颗粒的预测h_（avg）值与实验数据吻合。

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