Pool-boiling critical heat flux of water on small plates: Effects of surface orientation and size

Abstract

A series of experiments have been performed to understand the pool-boiling critical heat flux (CHF) behavior on small plates, varying the inclination angle and size of the heated surface under near atmospheric pressure: the first-phase experiment to clarify the CHF behavior at near the horizontal downward-facing position and the second-phase experiment to find out the general CHF behavior for overall inclination angles. The first-and second-phase experiment were performed for the inclination angles from -90 degrees (horizontally downward position) to -40 degrees using two plate-type test sections (20x200 mm and 25x200 mm) submerged in a pool of saturated water and for overall inclination angles from -90 degrees to 90 degrees using two plate-type test sections (30x150 mm and 40x150 mm) submerged in a slightly subcooled water pool, respectively. The CHF generally decreases as its inclination approaches to -90 degrees, but there is a transition angle, at which the rate of decrease in the CHF suddenly changes. The measured CHF is lower for the wider test section due to the increased difficulty of bubble escape and this size effect increases as the inclination angle approaches to -90 degrees. (C) 1997 Elsevier Science Ltd.