Apparent wall heat transfer coefficient in packed beds with cocurrent gas-liquid downflow

Radial effective thermal conductivity and apparent wall heat transfer coefficient were measured from temperature profiles in cocurrent air-water downflow through beds packed with glass spheres of 3 different sizes (0.12-0.43 cm). This paper concerns the apparent wall heat transfer coefficient. In the range of low liquid flow rate, the apparent wall heat transfer coefficient increased slightly with gas and liquid flow rates. In the range of high liquid flow rate, it depended only on liquid flow rate and increased with it. The apparent wall heat transfer coefficient was analyzed based on a heat transfer model which accounted for heat transfer related to gas and liquid flows and for that independent directly of gas and liquid flows. For the former, equations obtained in previous work were applied, and terms expressing the latter were determined from experimental data. The heat transfer independent of gas and liquid flows was correlated well in terms of dynamic holdup by empirical equations, which depended on particle diameter. © 1979, Society of Chemical Engineers, Japan. All rights reserved.