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ISSN Online: 2377-424X

ISBN CD: 1-56700-226-9

ISBN Online: 1-56700-225-0

International Heat Transfer Conference 13
August, 13-18, 2006, Sydney, Australia

COUNTER-CURRENT FLOW QUENCHING OF VERTICAL-NARROW-ANNULAR FLOW PASSAGES

Get access (open in a dialog) DOI: 10.1615/IHTC13.p12.230
13 pages

Abstract

Quenching of thin-gap annular flow passages by gravitational liquid penetration was examined by using water. The annular gap spacings tested were 10, 5.0, 2.0, 1.0 and 0.5 mm. The quenching was observed for the gap spacing above 1.0 mm. As the gap spacing became narrow, the cooling time became long. The area-averaged heat flux during the film boiling period before the rewetting occurrence decreased as the gap spacing decreased. The water-covered surface area before the rewetting occurrence decreased as the gap spacing decreased. The area-averaged peak heat flux during the rewetting period decreased as the gap clearance became narrow. However, the peak heat flux decrease was much smaller than that in the steady heat transfer critical heat flux. The area-averaged peak heat flux was well expressed by multiplying the critical heat flux of the pool boiling by the water-covered surface ratio. After the initiation of the rewetting, the water penetration into the flow passage was restricted by the flooding occurrence at the top entrance. Rewetting simulation was performed by solving the transient heat conduction equation. The boiling curve of the pool boiling was imposed as the boundary conditions in the simulation. It was proved that the precursory cooling before the rewetting occurrence was important to determine the rewetting velocity. When the water-covered surface ratio was introduced and the usual pool boiling curve was applied only to the water-covered surface and also the water penetration restriction due to the flooding occurrence at the top entrance was properly incorporated into the analyses, the rewetting velocities were predicted satisfactorily.