循环床非流化回料管内竖管传热的强化

ENHANCEMENT OF VERTICAL TUBE HEAT TRANSFER TO NON-FLUIDIZED MOVING BED IN RETURN LEG OF CIRCULATING FLUIDIZED BED

非流化移动床内颗粒的流动为柱塞流，颗粒间无相对运动，竖管传热主要靠颗粒间导热。由于导热热阻大，在管壁周围的颗粒吸热后不易传出，而在其周围形成一个热边界层，阻止了传热。利用在竖管上加上的扰流圈，使近壁处颗粒发生扰动，而使热颗粒传出，冷颗粒得以进入管壁周围，从而起到强化传热的作用。强化后的平均传热系数可增加２０％左右。平均传热系数值可达２２０Ｗ／（ｍ￣２·Ｋ）。

The solids flow in non-fluidized moving bed is plug flow in which solids have no relativemovement.The heat transfer in it depends mainly on heat conduction. Due to large thermalresistance among solids, the heated solids around wall of heated tube is difficult to transfer out-side,so it forms a thermal boundary of solids near the wall of tube,which deters the heattransfer. When some disturbing circlets are fixed on the vertical tube to disturb the solids nearthe tube ,the heated solids near the tube will be transfered out by disturbing circlets and coolfresh solids will be transfered in,therefore heat transfer is enhanced.The heat transfer coeffi-cients increase 20% by the enhancement ,and the mean heat trasnsfer coefficients are about22OW/(m￣2·K)。