Flow and heat transfer during a single drop impact on a liquid film

ABSTRACT

A two-dimensional incompressible laminar computational model was established to analyze flow and heat transfer characteristics during a single liquid drop impinging onto a liquid film, with an underneath surface of relatively low temperature. Using the coupled level set and volume of fluid method, the gas–liquid interface at different time sequences can be obtained clearly. Concerning the heat transfer process, three different factors including impact velocity, film thickness, and drop diameter were discussed. Results indicate that liquid inside the film can be classified as three zones: the impact zone, the transition zone, and the static zone, specifically according to different heat flux. Average surface heat flux can be increased by increasing impact velocity, while effects of film thickness and drop diameter are minor. Corresponding mechanisms were interpreted as well. For heat flux distribution in the impact and transition zones, both film thickness and drop diameter influence the distribution greatly. With an increment in film thickness and drop diameter, heat flux in the impact zone decreases, while heat flux in the transition zone appears to be an opposite trend. Also in the transition zone, the fluctuation amplitude of the heat flux rises as the two factors are reduced.

Nomenclature

ddrop	=	drop diameter
h	=	liquid film thickness
	=	interface normal vector
t	=	time
v	=	impact velocity
q	=	heat flux
	=	average heat flux
κ	=	interface curvature
α	=	volume fraction
φ	=	signed distance

Nomenclature

ddrop	=	drop diameter
h	=	liquid film thickness
	=	interface normal vector
t	=	time
v	=	impact velocity
q	=	heat flux
	=	average heat flux
κ	=	interface curvature
α	=	volume fraction
φ	=	signed distance