Heidelberg 2015 – wissenschaftliches Programm
UP 13.27: Poster
Donnerstag, 26. März 2015, 10:45–19:45, G/Foyer
Comparison of Parametrizations for Bubble-induced Gas Exchange — •Wolfgang Mischler and Bernd Jähne — Institut für Umweltphysik, Heidelberg, Deutschland
Common parametrizations for bubble mediated gas transfer are compared on a basis of systematic measurements of gas transfer rates at a dedicated bubble tank. Trace gas concentrations were measured using a quadrupole mass spectrometer with a silicone membrane inlet in the water phase of the tank. Fourteen trace gases with a wide range of solubilities and diffusivities – SF6, Neon, N2, HD, D2, O2, Krypton, Pentafluoroethane, Xenon, N2O, C2H2, CH3Cl, Benzene and DMS – were used to investigate the dependency on these two physico-chemical parameters. Bubbles were generated by a water jet with adjustable kinetic energy, which entrained a controllable gas volume flux into the water tank. Invasion and evasion experiments with a variety of conditions were conducted including salt water (1.75 % NaCl), the addition of the soluble surfactant Triton X-100, n-butanol and glycerol.
Existing models for bubble mediated gas transfer are tested. Simple power law dependencies turn out to be incapable to describe the transfer for the whole range of solubilities and diffusivities. An extension of the parametrization proposed by Woolf fits the data best. A simple model using only 2 parameters is proposed. Its performance is almost as good as the extended Woolf model.