Nuclear Technology / Volume 154 / Number 1 / April 2006 / Pages 13-40
Technical Paper / Thermal Hydraulics
This paper addresses the pool boiling critical heat flux (CHF) phenomena in one-dimensional inclined rectangular channels by changing the orientation of a copper test heater assembly. In a pool of saturated water at atmospheric pressure, an account is taken of the gap sizes of 1, 2, 5, and 10 mm and the surface orientation angles from the downward-facing position (180 deg) to the vertical position (90 deg). Tests are conducted on the basis of the visualization of boiling phenomena utilizing a high-speed digital camera. In addition, an engineering correlation relating to the CHF near the vertical position is developed anchored in the experimental results. It is observed that the CHF generally decreases as the surface inclination angle increases and as the gap size decreases. In the downward-facing position (180 deg), on the other hand, the vapor escape and liquid refill are accelerated by the squeezing gap so that the CHF tends to increase as the gap size decreases. It is also found that there exists a transition angle, around which the CHF changes with a rapid slope on account of the CHF triggering mechanism differing with the inclination angle.