Photographic study of high-flux subcooled flow boiling and critical heat flux |
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Authors: | Hui Zhang Issam Mudawar Mohammad M. Hasan |
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Affiliation: | 1. Boiling and Two-phase Flow Laboratory, School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907, USA;2. NASA Glenn Research Center, 21000 Brookpark Road, Cleveland, OH 44135, USA |
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Abstract: | This study examines both high-flux flow boiling and critical heat flux (CHF) under highly subcooled conditions using FC-72 as working fluid. Experiments were performed in a horizontal flow channel that was heated along its bottom wall. High-speed video imaging and photomicrographic techniques were used to capture interfacial features and reveal the sequence of events leading to CHF. At about 80% of CHF, bubbles coalesced into oblong vapor patches while sliding along the heated wall. These patches grew in size with increasing heat flux, eventually evolving into a fairly continuous vapor layer that permitted liquid contact with the wall only in the wave troughs between vapor patches. CHF was triggered when this liquid contact was finally halted. These findings prove that the CHF mechanism for subcooled flow boiling is consistent with the interfacial lift-off mechanism proposed previously for saturated flow boiling. |
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Keywords: | Critical heat flux Flow boiling Subcooled boiling |
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