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Study on Initiation of Localized Wetting During Film Boiling Near the MHF Point in Spray Cooling
Niro Nagai and Haruka Obe

This paper reports experimental results of both visual observation for liquid-solid contact situations and surface temperature measurement simultaneously when liquid spray cooled superheated surface by boiling. The focus is on how and when localized liquid-solid contact on superheated surface appears, which is important for revealing boiling mechanism near MHF point. A single crystal sapphire plate was cooled by HFE-7100 liquid spray from film boiling to transition boiling situation. The obtained results show that wetting initiation temperature was affected by initial surface temperature, liquid flow rate density and spray nozzle position, i.e. distance from the center position of the surface. Wetting initiation temperature mostly ranged between Leidenfrost temperature and spontaneous nucleation temperature of HFE-7100.

Keywords: Boiling, Heat transfer, Wetting, Visual observation, Liquid-solid contact, Spray cooling, MHF point, Spontaneous nucleation

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