Study of the Mechanism of Burn-Out in Boiling System of High Burn-Out Heat Flux

Abstract

Burn-out phenomena are studied for two special systems of boiling which are both realized in the saturated nucleate boiling of water at atmospheric pressure on a horizontal 10mm dia. copper heated surface.First, it is attempted by mechanical means to cause a forced collapse of the vapor masses which are generated periodically on the heated surface. In this case, burn-out heat flux qc increases, but the velocity of fluid movement concerned with the collapse of vapor mass is restricted so that the increase of qc is limited.Second, the heated surface is supplied with liquid by means of a small liquid jet. In this case, burn-out appears with a mechanism which is different from ordinary pool boiling. Splashing of liquid due to the violent effusion of vapor from the heated surface interrupts the part of supplied liquid in reaching the heated surface so that the quantity of liquid on the heated surface balances finally the heat flux, and burn-out occurs. For the burn-out of this type, qc can be increased steadily by increasing the velocity of liquid jet.