Annual Reviews of Heat Transfer

ISSN 1049-0787

Year 2000

Volume 11

642 pages

Volume price - $141.00

D. Attinger
Department of Mechanical Engineering, State University of New York at Stony Brook, Stony Brook, New York, USA

S. Haferl
Laboratory of Thermodynamics in Emerging Technologies, Institute of Energy Technology, Swiss Federal Institute of Technology, CH-8092 Zurich, Switzerland

Z. Zhao
Broadcom Corporation, Irvine, CA 92618-3603, USA

Dimos Poulikakos
Laboratory of Thermodynamics in Emerging Technologies, Department of Mechanical and Process Engineering, Institute of Energy Technology, Swiss Federal Institute of Technology (ETH), ETH Center, Zurich, Switzerland

The fundamental problem of a liquid droplet impacting on a surface appears in a wide range of phenomena from nature to technology. It offers a great many scientific challenges that cover the entire area of transport phenomena. In fluid dynamics, even in the limit of Newtonian liquids, the problem involves a severely deforming free liquid surface that interacts with a gaseous environment, on the one hand, and with a solid surface, on the other. Complex wetting, breakup, and re-coalescence phenomena may take place. The thermodynamic/heat transfer complexities can be exemplified if one considers the case where the impacting droplet is molten and solidifies upon impact. In addition to the interplay of the three heat transfer modes and thermocapillarity, the solidification may occur under nonequilibrium conditions. Mass transfer phenomena can also be present in the molten droplet impact problem. Adsorption and surfactant presence, for example, can give rise to a dynamic behavior of the surface tension during the droplet deformation. In the case of a molten metal in an oxidizing environment, the formation of oxides and their impact on the surface tension can affect the process profoundly. The opposite thermodynamic limit of a droplet evaporating upon impact on a surface can also serve to underline the relevant heat and mass transfer challenges, but it is outside the scope of this review article. The purpose of this pair of articles (Parts 1 and 11) is to review the state of the art of the droplet/surface impact problem as it pertains to the deposition of molten droplets, and to identify trends of future research driven by emerging technologies. Part I (Chapter 2) focused on the fluid dynamics of the problem in the absence of the temperature gradients. Part II, which comprises the present review, discusses works relevant to the case where a temperature gradient exists in the absence as well as in the presence of solidification of the droplet material, the latter area being the main scope of this review. Following the trend of published work, the review focuses primarily on metal droplet solidification. Nonequilibrium phenomena during phase change, contact resistance effects and nucleation phenomena are integral parts of the review. Phenomena at the microscopic and submieroscopic scales are also discussed, in addition to their macroscopic counterparts.

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