Friction

, Volume 6, Issue 1, pp 62–74 | Cite as

Thermocapillary migration mechanism of molten silicon droplets on horizontal solid surfaces

Open Access
Research Article
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Abstract

Effective lubrication under extreme conditions such as high temperature is of considerable importance to ensure the reliability of a mechanical system. New lubricants that can endure high temperatures should be studied and employed as alternatives to traditional oil-based lubricant. In this paper, a thermocapillary model of a silicone-oil droplet is developed by solving the Navier–Stokes and energy equations to obtain the flow, pressure, and temperature fields. This is accomplished using a conservative microfluidic two-phase flow level set method designed to track the interface between two immiscible fluids. The numerical simulation accuracy is examined by comparing the numerical results with experimental results obtained for a silicone-oil droplet. Hence, the movement and deformation of molten silicon droplets on graphite and corundum are numerically simulated. The results show that a temperature gradient causes a tension gradient on the droplet surface, which in turn creates a thermocapillary vortex. As the vortex develops, the droplet migrates to the low-temperature zone. In the initial stage, the molten silicon droplet on the corundum substrate forms two opposite vortex cells, whereas two pairs of opposite vortices are formed in the silicone fluid on the graphite substrate. Multiple vortex cells gradually develop into a single vortex cell, and the migration velocity tends to be stable. The greater the basal temperature gradient, the stronger the internal thermocapillary convection of the molten silicon droplet has, which yields higher speeds.

Keywords

molten silicon droplet temperature gradient thermocapillary migration 

Notes

Acknowledgements

The authors appreciate the support from the Key Program of the National Natural Science Foundation of China (Grant No. 51335002) and Key support projects of strategic emerging industries in Jiangsu Province (Grant No. 2015-318).

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© The author(s) 2017

Open Access: The articles published in this journal are distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

Authors and Affiliations

  1. 1.School of Mechanical EngineeringChangzhou UniversityChangzhouChina
  2. 2.Collaborative Innovation Center of Photovoltaic Science and Engineeringthe Breeding Construction Point of State Key Laboratory of Photovoltaic Engineering ScienceChangzhouChina

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