Résumé du preprint DAPNIA-07-51

Heat transfer characteristics of two-phase He I (4.2 k) thermosiphon flow
L. Benkheira, B. Baudouy, M. Souhar
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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