Heat transfer characteristics of two-phase He I (4.2 K) thermosiphon flow |
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Affiliation: | 1. DAPNIA, SACM-LCSE, CEA–Centre de Saclay, 91191 Gif-Sur-Yvette cedex, France;2. Laboratoire d’Énergétique et de Mécanique, Théorique et Appliquée LEMTA, ENSEM, CNRS UMR 7563, 2, Avenue de la forêt de Haye, B.P. 160, 54504 Vandoeuvre cedex, France;1. Laboratory of Fundamental Science on Ergonomics and Environmental Control, School of Aeronautic Science and Engineering, Beihang University, Beijing 100191, PR China;2. Shenyuan Honors School, Beihang University, Beijing 100191, PR China;3. Beijing Key Laboratory of Space Thermal Control Technology, Beijing Institute of Spacecraft System Engineering, China Academy of Space Technology, Beijing 100094, PR China;4. George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA |
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Abstract: | In the framework of the cryogenic cooling system design of a large superconducting magnet under construction at CERN-Geneva, heat transfer in two-phase He I natural circulation loop has been investigated experimentally. The experiments were conducted on a 2 m thermosiphon loop with copper tube of 10 mm inner diameter uniformly heated over a length of 0.95 m. All data were obtained near atmospheric pressure. Evolution of the exit vapour quality and wall superheat as a function of heat flux are presented and analyzed. A comparison between the two-phase heat transfer coefficient hTP determined in our study and the most relevant correlations available in literature is made. Further, we predict hTP with a correlation based on the combining effects of forced convection and nucleate boiling by a power-type asymptotic model. Finally, we present the boiling crisis study and we propose a critical heat flux correlation as a function of channel height to diameter ratio (z/D) to model our experimental results. |
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