Experimental study on pool transition boiling with downward facing heated surface

Experimental study was conducted to examine the pool boiling occurring on a relative large downward facing surfaces confined space with width of 2.2, 2.6, 3.0, 3.2 and 13.0 mm, respectively, at atmospheric pressure using water as the working fluid. The boiling curves of distilled water with downward facing heated surface were obtained. The heat flux on downward facing heated surface is less than one tenth of that on upward facing heated surface. The effects of wall superheat, ΔT_w, and gap size, δ, on transition boiling were also analyzed. The results show that Nu decreases with the increasing of ΔT_w under transition boiling condition. And increases generally with the increasing of gap size, δ, though there is a small peek on Nu-δ curve in narrow gap size area.