An experimental study of saturated pool boiling from downward facing and inclined surfaces

Abstract

Pool boiling curves for inclinations of 0° (downward facing), 5°, 10°, 15°, 30°, 45°, and 90° are obtained by quenching a 12.8-mm thick copper disk having a diameter of 50.8 mm in a pool of saturated water. Results show that nucleate boiling heat flux decreases as the angle of inclination is increased. However, the decrease in nucleate boiling heat flux with inclination is more pronounced at lower wall superheats. Conversely, the transition boiling heat flux and both q CHF and q min , as well as the corresponding wall superheat, increase with surface inclination. The quenching time of a downward facing surface having an initial wall superheat of 160 K is about six times that for a 5° inclination and 23 times that for a 90° inclination. For all inclinations, quenching always begins at the lowermost position and propagates upward. The average quenching velocity of about 2.6 cm s −1, is almost constant for θ⩾ 45°, but increases rapidly with the decrease in surface inclination reaching approximately 6.3 cm s −1 at 0°.