Mass transfer to thin liquid films on rotating surfaces, with and without chemical reaction

Abstract

This investigation was concerned with the ability of perforated discs to act as the active mass transfer surface in rotary contact devices. Of particular interest were discs constructed of a woven stainless steel mesh. This material had a high fractional free area and an irregular surface, which is desirable if interfacial turbulence is to be promoted. The characteristics of three grades of mesh were compared with those of a plate perforated with punched holes and a smooth plane disc. A hydrodynamic study indicated that a stable film could be maintained on these flexible materials at speeds in excess of 200 RPM. However it was also demonstrated that at higher speeds dry areas tended to form around the periphary. The mass transfer performance was analysed in a specially designed rotary test rig using a carbon dioxide/water system. These experiments indicated that high transfer rates are attainable provided that operation is restricted to conditions where film breakdown does not occur. At 1500 RPM flowrates in excess of 200 cm 3 /sec must be utilised. The same apparatus was adapted so that the enhancement due to a chemical reaction in the liquid phase could be determined. Aqueous solutions of diethanolamine were used in these experiments. The results were compared with predictions based upon a penetration type theory. The results of the investigation were applied to the design of a scrubber for an underwater closed—cycle nitro diesel engine and conclusions as to the relative merits of physical and chemical systems made.