2006 Fiscal Year Final Research Report Summary
Deformation behavior and heat transfer of droplets successively impinging onto a solid substrate
| Project/Area Number |
16560185
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Thermal engineering
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| Research Institution | Kyoto University |
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Principal Investigator |
FUJIMOTO Hitoshi Kyoto Univ. School of Energy Science, Associate Professor, エネルギー科学研究科, 助教授 (40229050)
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| Co-Investigator(Kenkyū-buntansha) |
TAKUDA Hirohiko Kyoto Univ. School of Energy Science, Professor, エネルギー科学研究科, 教授 (20135528)
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| Project Period (FY) |
2004 – 2006
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| Keywords | droplet / interaction phenomena / numerical simulation / spray cooling / photography / free surface |
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| Research Abstract |
The collision of two successive droplets with a hot solid is investigated by means of photography as a fundamental research on dilute spray cooling. Two water droplets fall vertically toward a horizontal dry surface. The leading droplet impinges onto the dry surface, followed by the second droplet which impacts coaxially onto the top of the deforming droplet after a certain interval. The interaction phenomena between droplets were focused on. At low surface temperature, the coalesced liquid is deformed into the shape of crown with its height increasing with droplet spacing. At a relatively high temperature at which many vapor bubbles appear at the liquid/solid interface during the collision, the coalesced liquid break up into many secondary small droplets. Little interaction of two droplets occurs for large droplet spacing. At temperatures far above the boiling temperature of liquid, a vapor layer is formed between the liquid and the solid surface. In cases of low impact inertia, the formation of liquid crown is observed, but the crown is distorted. Computer programs for analyzing the hydrodynamics and heat transfer of droplets were coded, taking into account of the effect of viscosity, gravity, surface tension, free surface, thermal dependence of physical properties, heat transfer between the liquid and the solid. The formation process of liquid crown on the solid at relatively low temperature or far above the boiling temperature of liquid was investigated in detail by computer simulations in an axisymmetric coordinate system. In addition, the oblique collision of droplets with a solid was studied by means of three dimensional simulation. The effect of impact angle on the deformation behavior of droplet was investigated at low impact inertia. The physics of the collision phenomena were addressed.
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