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International Heat Transfer Conference 15

ISSN: 2377-424X (online)
ISSN: 2377-4371 (flashdrive)

Non-Equilibrium Discharging Flow From Safety Valves

Yoshihiko Kitagawa
Tokyo University of Marine Science & Technology

Sachiyo Horiki
Tokyo University of Marine Science and Technology, Etchujima 2-1-6, Koto-ku, Tokyo 135-8533, Japan

Masahiro Osakabe
Tokyo University of Marine Science and Technology, Etchujima 2-1-6, Koto-ku, Tokyo 135-8533, Japan

DOI: 10.1615/IHTC15.tpf.009810
pages 8405-8419


KEY WORDS: Two-phase/Multiphase flow, Boiling and evaporation, Non-equilibrium, Discharging Flow, Vena Contraction, Safety Valve

Abstract

The discharging flow rate from the safety valve at different lifts and disk materials was verified with the simple disk-type flow contraction. The water discharging flow rate was measured and compared with the Bernoulli model. The discharging coefficient of water was approximately 0.6 in spite of the lift, which was mainly due to the vena contraction at the minimum flow area. The air discharging flow rate was also measured and well predicted with the expansion delay model. The expansion delay was introduced as the rapid flow-directional change enhanced the non-equilibrium behavior of disk-type contraction. Furthermore the discharging flow rate with flashing was measured at the different inlet subcooling or two-phase quality. The non-equilibrium flashing flow model directly using the steam table was proposed to obtain the critical mass flux at the vena contraction. The comparison of the experimental results with the non-equilibrium model indicated the significant nonequilibrium in the flashing flow at the vena contraction in spite of the disk material. The subcooled liquid and two-phase discharging behavior was carefully observed by using the transparent disk. The observation showed the significant delay of boiling indicating the strong non-equilibrium. The two-phase discharging flow rate at the strong non-equilibrium was well correlated with the simple pressure loss correlation using the specific volume of water.

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