INFLUENCE OF VISCOSITY AND FOAMING PROPERTIES ON HEAT-TRANSFER IN PACKED-BED WITH COCURRENT UPFLOW OF GAS AND LIQUID

The authors investigate radial heat transfer in packed columns with cocurrent upflow of gas and liquid. The gas is saturated nitrogen and the liquids are aqueous solutions of either ethylene glycol (viscous) or pentanol (foaming), or pure water. The influence of liquid properties on hydrodynamics and heat transfer parameters is shown. The operating parameters have been varied in the range of 5.4 less than or equal to Pr less than or equal to 22.6 for the liquid Prandtl number, 2 less than or equal to Re-l less than or equal to 50 (up to 125 for water in single phase flow) for the liquid Reynolds number and 0 less than or equal to Re-g less than or equal to 30 for the gas Reynolds number. The particle diameter is 2 mm and the reactor inner diameter is 100 mm. The reactor is heated by a constant heat flux through its wall. Radial temperature profiles are measured inside the packed bed. The heat transfer parameters of the packed bed reactor are obtained by fitting the parameters of a two-dimensional, homogeneous model to the measured profiles (the radial effective thermal conductivity of the packed bed, Lambda(r), and the wall heat transfer coefficient alpha(W)). The liquid holdup is measured by conductimetric probes, using a salt tracer technique. In single phase liquid flow, the packed bed conductivity increases first linearly with the fluid flow rate, but tends to increase stronger than linearly at higher liquid Reynolds number (Re-l > 80). The packed bed conductivity decreases with increasing liquid viscosity. In two-phase flow, the heat transfer is influenced by the flow regimes. Flow regimes and liquid holdup measurements are first presented and then heat transfer parameters are discussed. Results are compared to existing correlations and a new correlation is proposed. The packed bed conductivity also decreases with liquid viscosity but increases with foaming in two-phase flow.