CIESC Journal

• 化工学报 • 上一篇    下一篇

流体流过填充床层冷却之传热系数

朱葆琳,游文泉   

  1. 中国科学院石油研究所 ,中国科学院石油研究所
  • 出版日期:1957-12-25 发布日期:1957-12-25

COOLING OF FLUIDS THROUGH PACKED BEDS

CHU PAO-LIN Yu WBN-CHUAN Institute of Petroleum, Academia Sinica   

  • Online:1957-12-25 Published:1957-12-25

摘要: 填充床层之传热系数包括二重阻力,即床层内部的传热阻力和床层与管壁界面间薄膜的传热阻力。本文以空气和水为传热介质,使其流过填充床层冷却,改变操作条件和床层构造,考察了Pr准数,床层高度、填充物的导热系数和形状对於传热系数的影响。由於高速固定床接触反应器和填充热交换器逐渐在工业上取得了应用,高线速下的传热数据需要迫切,因此试验的范围采用了较大的Re准数。 玻璃或磁质等低导热系数球状填充物的传热系数可归纳成: 试验范围: D_p/D_t=0.08~0.5; L/D_t=10~30; Re=250~6500; Pr=0.722~4.8 铜、铁等高导热系数球状填充物的传热系数可归纳成: 试验范围; D_p/D_t=0.1~0.5; Re=300~10,000;   L/D_t=10~30 在此范围内所有试验皆经过二次以上的重复试验,误差一般不大於5%。 以圆柱体为填充物的传热系数,仅须将修正Re准数中的几何量D_p,改成与圆球具有相同的几何表面面积的球径D_p即可。 以上二式说明流体的物理性质即Pr准数对传热系数的影响不很显著,床层高度对传热系数的影响:低导热系数填充物的传热系数随L/D_t比率之减小而逐渐增大,L/D_t>30,影响甚微,L/D_t=20,误差约7%,L/D_t=10,误差可达15%;高导热系数填充物的传热系数随L/D_t的增大略有增大的趋势,但影响

Abstract: In this paper the influence of Pr number, shape and thermal conductivity of the packing material and the bed height on the heat transfer coefficients of the packed beds have been thoroughly studied when air and water were cooled through packed tubes. In order to offer the data for the design of fixed bed, catalytic reactors and packed heat exchangers operated at high space velocity, high Re number was adopted. In case of spherical packings of low thermal conductivity, such as glass, ceramics, the heat transfer coefficient may be correlated as follows: experimental ranges: Dp/Dt = 0.08~0.5; L/Dt = 10~30; Re = 250~6500; Pr= 0.722~4.8. In case of shperical packings of high thermal conductivity such as copper, iron, the heat transfer coefficient may be correlated as follows:Nu = 2.17 Re0.52 . experimental ranges: Dp/Dt = 0.1~0.5; Re = 300~10;000; L/Dt = 10~30. Within above ranges, all experiments were repeated at least twice, the error was not greater than 5%. For the cylindrical packings, the particle diameter in the Re number of the above equations should be changed into the equivalent diameter of a sphere which has the same surface area as the cylinder.