Tetsu-to-Hagane
Online ISSN : 1883-2954
Print ISSN : 0021-1575
ISSN-L : 0021-1575
Experimental Study of Deformation Process of a Water Droplet Impinging on Polished and Rough Surfaces Heated to above the Leidenfrost Temperature
Hitoshi FUJIMOTOTakashi FUKUINatsuo HATTA
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1996 Volume 82 Issue 12 Pages 975-980

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Abstract

This paper treats the comparison of the deformation process of a water droplet impinging upon a hot polished (smooth) surface with that upon a hot oxide scaled (rough) surface. The surface whose material is SUS304 stainless steel, has been heated to 773K for both the smooth and rough cases and a water droplet diameter has ranged between 0.3mm to 0.7mm. The rough surface has been made artificially by rapid-quenching the impingement side of the test surface piece, which has been heated to 1273K in a furnace for about three hours, by water spraying. Thereby, the so-called oxide film has been formed on the surface. The droplet deformation process has been measured for the two cases where the droplet is struck on the smooth and rough surfaces, keeping the other experimental conditions constant. The deformation process has been found to be significantly different between the smooth and rough cases. The irregularity of the droplet configuration on the rough surface has been found to occur even in a short time after collision and to be amplified as the droplet deformation proceeds. For various Weber numbers, it has been found that the time needed for a droplet to reach a maximum diameter on surfaces can not be arranged as a function of the Weber number alone. Again, the difference between the smooth and rough cases becomes remarkable with increasing the Weber number.

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© The Iron and Steel Institute of Japan
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