Heat Transfer in a Packed Bed with Gas-Liquid Cocurrent Upflow

Abstract

Radial effective thermal conductivity and apparent wall heat transfer coefficient in a packed bed with gas-liquid cocurrent upflow were measured in air-water system with three kinds of spherical particles of d_p =4.0, 5.0 and 6.0 mm diameter. The following results were obtained :
1) The effective thermal conductivity, k_er, and wall heat transfer coefficient, hω, in the cocurrent upflow system are larger than those in the cocurrent downflow system.
2) Increasing the gas flow rate, G, while holding any constant liquid flow rate, L, kerand hω, in the downflow system increase gradually. Those in the upflow system increase temporarily in the bubble-flow region, and then decrease gradually or are constant in the pulse-flow region.
3) In the range of high gas flow rate in which k_er decreases gradually,
k_er/k_l=c (d_pL/μ_l) ^a (d_pG/μ_g) ^b
(a=0.550.57, b=-0.3, c=22.526.9)
4) Experimental results of k_er for porous alumina spheres of 5.0 mm diameter are larger by about 20% than the estimated values of k_er for glass spheres of the same size. This suggests that particle surface roughness has an influence on the liquid holdup and on k_er.