COOLING OF FLUIDS THROUGH PACKED BEDS
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.