Turbulent Enhancement of Mass Transfer in Bubble Plumes

An experimental method was developed for measuring the mass transfer in water/air/carbon dioxide systems with pH-probes. Measurements of the mass transfer were made with respect to the parameters of desorption in bubble plumes. The investigations show a linear increase of the mass transfer with the gas flow rate. Furthermore, the mass transfer rate depends on the nozzle diameter, but not on that of the vessel. The mass transfer rates of the momentum dominated near field, of the buoyancy dominated far field, and of the free surface were separated experimentally. The probability density functions of the bubble size were determined with a photographic method as a function of the gas inlet conditions. Comparing the experimental results for the buoyancy dominated far field of the bubble plume with a basic microkinetic approach demonstrates that the turbulent flow does not increase the mass transfer by more than 10–20 %. Thus, a turbulence factor of 2–3 in order to establish consistency between the theoretical considerations and the experimental results, as described elsewhere in the literature, is not required.