ON INCIPIENT-BOILING WALL SUPERHEATS IN LIQUID METALS

It is shown that good agreement between predicted and measured incipient-boiling wall super-heats can be obtained with Holtz's [4] original superheat model, if two additional factors are taken into consideration. The first of these is the loss of inert gas from the cavity between the time of maximum boiling suppression (MBS) and the time of the incipient boiling (IB) event The second of these is the probability that the radius of curvature of the liquid-vapor interface at IB may be significantly different from that at MBS. Based upon the recent experimental IB results obtained by Chen [5] on potassium and those obtained by Holtz and Singer [8] on sodium, the following tentative conclusions have been drawn: (a) The loss of inert gas from an active cavity between the time of MBS and that of the first IB event appears to be negligibly small, but it can be considerable if a large number of IB events follow a single MBS treatment; (b) Bubble radius at IB is about 3 4 that at MBS; (c) Surface finish for standard smooth surfaces would not appear to have a strong influence on IB superheats; (d) The apparent heat-flux effect could possibly be in reality an inert-gas effect. © 1969.