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ISSN Online: 2377-424X

ISBN Print: 978-1-56700-421-2

International Heat Transfer Conference 15
August, 10-15, 2014, Kyoto, Japan

Visual Observation of Liquid-Solid Contact Situations on Superheated Surface Cooled by Liquid Jet or Spraying

Get access (open in a dialog) DOI: 10.1615/IHTC15.evp.009140
pages 2447-2455

Resumo

This paper reports experimental results on how localized liquid-solid contact on superheated surface appears and spreads and what kinds of parameters mostly affects this phenomena, which is important near MHF point. Previous researches reveal the effect of many parameters such as surface wettability, liquid subcooling, and physical properties of solid material, onto the MHF point. One of the authors succeeded to obtain visual images of liquid-solid contact situations during pool boiling by total reflection method, using transparent single crystal sapphire plate. In this paper, the authors tried to observe liquid-solid contact situations under two conditions; the superheated sapphire plate was cooled by either liquid spraying or jet impingement. These observations were intended to know how and when localized liquid-solid contact initiates and expands. The test liquid was HFE-7100, boiling point is about 60 °C. The solid surface was made of single crystal sapphire. The sapphire plate was put on a silicone oil bath, the temperature of which was controlled by cartridge heater up to 300 °C. The liquidsolid contact situations were successfully visualized for both conditions and obtained results were summarized as follows. 1) Initial surface temperature Twi, liquid velocity or flow rate and liquid temperature TL affect the liquidsolid contact situations considerably. 2) As the TL and Twi increases, the elapsed time when the liquid-solid contact initiated after the liquid jet or spray firstly impacted on the surface is delayed. 3) The situations how the liquid-solid contact area expands on the surface are different between liquid jet and spraying.