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ICLASS 94<br>Proceedings of the Sixth International Conference on Liquid Atomization and Spray Systems

ISBN:
978-1-56700-019-1 (Print)
978-1-56700-445-5 (Online)

DISCHARGE CHARACTERISTICS OF CRYOGENIC FLUIDS FROM A PRESSURIZED VESSEL

J.C. Yang
Building and Fire Research Laboratory, Gaithersburg, USA

W.M. Pitts
Building and Fire Research Laboratory, Gaithersburg, USA

B.D Breuel
Building and Fire Research Laboratory, Gaithersburg, USA

G. Gmurczyk
Building and Fire Research Laboratory, Gaithersburg, USA

W. Rinkinen
Building and Fire Research Laboratory, Gaithersburg, USA

W. Cleveland
National Institute of Standards and Technology, Gaithersburg, USA

Abstract

An experimental technique to study the rapid release of liquid cryogenic fluids from a pressurized vessel orientated downward is described. A rupture disc was used as the release mechanism. Experimental observations were made on the discharge characteristics of two cryogenic fluids, C4F10 (FC-31-10) and C3F8 (FC-218), which were proposed as potential candidates for replacement of halon 1301 (CF3Br) as fire suppressant. For comparison, halon 1301 was also included in this study. Various parameters that could influence the discharge process were studied. These parameters were: (1) orifice opening, (2) the effect of an extension tube at the vessel exit, and (3) initial charge pressure. The events occurring internal and external to the vessel during discharge of FC-31-10 or FC-218 were studied with high-speed photography and a transparent acrylic vessel. The average penetration velocities of the spray at various locations downstream were measured by means of a laser extinction technique. Two distinct flashing behaviors were observed at the vessel exit. The first flashing occurred immediately after the bursting of the rupture disc, and the second appeared at or before the moment the liquid was depleted from the vessel. During depressurization, no internal boiling of FC-31-10 or FC-218 was observed. Increasing the initial charge pressure reduced the emptying time of the liquid. Decreasing the orifice opening was found to increase the liquid emptying time significantly. The behavior of the liquid inside the vessel was found to be very similar whether an extension tube was present or absent at the vessel exit: an indication of two-phase critical flow.