The point of the distribution of water droplet flow is upper than the point on the washing center. In the case of the washing of glycerin, the washed area in 1 second is about 420 cm2, the washing of 1 cm2 needs 0.25 cm3 of wash water
3.2 Washing with falling water film flow
The relation between the test liquid film thickness and the liquid viscosity is shown in Fig.7. The film thickness changes from about 15 μm to 54 μm as the viscosity changes from 1 to 2000 mPa・s. The relation between the rate of washing and the liquid viscosity is shown in Fig.8. The rate of washing out the clinging liquid film hα is from 18 to 29μm. In the case of high viscosity liquid, it needs the more time to wash out clinging liquid because of the thickness of clinging film thickness.
Fig.5. Comparison between Water Droplet Flow and Water Jet Flow in Washing (ethylene glycol)
4. Conclusion
In the case of the washing of water soluble liquid with water droplet flow, the extent area of water droplet flow is washed at the same lime. The effect of the clinging liquid viscosity is small. The state of water droplet flow is washed in about 1 second. The washing of 1 cm2 area needs about 0.25 cm3 water. When water-soluble clinging liquid can be washed with falling water flow easily, and when the film Reynolds number is 1900, the rate of the clinging liquid carded out is about 18〜29 μm/s. Therefore the water quantity of wash water can be reduced with using small diameter nozzle in the case of water-soluble liquid.
Fig.7 Clinging Liquid Film Thickness on Test wall concerning the Viscosity of the Test Liquids
Fig.8 Rate of washing out adhered liquid concerning the viscosity of the test liquids
5. Reference
(1) Ministry of Transport, The International Convection for the Prevention of Pollution from Ships, 1973 as Modified by the Protocol of 1978 Relating Thereto (MARPOL 73/78) (1994 Edition), Kaibundo, p262
(2) Schuurmans, H. J. A. and Schilder, J. G. M., Prewash Procedurees for Chemical Tankers, Monograph Published by The Netherland Marine Institute, 1979
(3) Verbeek D. G. F. and Van Den Akkeen, H. E. A., Research on More Efficient Tank Cleaning Methods: A Fundamental Study, Delft University of Technology, 1990
(4) Ueda, K., Tank Washing of Chemical Tanker, Papers of Ship Research Institute, Vol.28 No.3, May 1991
(5) Ueda, K. and Yamanouchi, H., Tank Washing of Chemical Tanker 3rd INTERNATIONAL Marine Engineering Conference, 1996, Shanghai China, P 1-14-1〜8
(6) Bauer, H/, VDI Forsch-h, 22-457, 1956
