Library Subscription: Guest

ISSN Online: 2377-424X

ISBN Print: 0-85295-345-3

International Heat Transfer Conference 10
August, 14-18, 1994, Brighton, UK

AN EXPERIMENTAL AND ANALYTICAL STUDY ON CHF PHENOMENON APPEARING IN A BOTTOM-CLOSED VERTICAL TUBE FOR VAPOR/LIQUID DENSITY RATIO IN THE RANGE OF 0.000624-0.136

Get access (open in a dialog) DOI: 10.1615/IHTC10.1290
pages 461-466

Abstract

Critical heat flux (CHF) caused in a bottom-closed vertical tube has characteristics quite different from those of the ordinary type of CHF. Paying attention to this nature, careful measurements of CHF have been conducted for boiling of water, R-113, and R-22 in tubes, providing a data set of CHF in wide ranges of the vapor/liquid density ratio (0.000624-0.136), the latent heat of evaporation (112-2257 kJ/kg), and the tube geometry (8-16 mm diameter;160-960 mm length). In this boiling system, countercurrent two-phase flow is originated in the tube with the highest mass flow rate of vapor and liquid at the top end. CHF is then presumed to occur when the steady-state two-phase flow in the tube is deteriorated by the limit condition of countercurrent annular flow at the top end. Based on this idea, the limit condition derived theoretically for the existence of the steady-state countercurrent annular flow is compared with the foregoing CHF data, and its affirmative result suggests not only the validity of the mechanism assumed above for the onset of CHF but also the usefulness of the proposed theoretical model to predict CHF in this boiling system.