Temperature wave propagation as a route from nucleate to film boiling?

The understanding of the phenomenology of critical heat flux (CHF) is still very controversial. Despite many explanation models for CHF proposed so far, intractions of the fluid with the temperature field in the heater is often neglected. Based on the mathematical theory of reaction-diffusion systems a new mechanistic model accounting for the interdependence of heat conduction and boiling heat transfer is presented. It offers a physically sound explanation for 'how' and 'why' transition from nucleate to film boiling inevitably occurs after reaching CHF. It will be shown that transition from nucleate to film boiling can be viewed as the inception of a temperature wave travelling in the heater triggered by a number of dry spots as these spread out and cover the boiling surface. An expressed difference in the qualitative behaviour of thin and thick heaters is identified. Hence, extrapolation of results obtained with thin heaters to technically relevant thick heaters is questionable. (orig.)Also published in: Two-phase flow modelling and experimentation, Celata, G.P.; DiMarco, P; Shah, R.K. (eds.) v. 1(1999) p. 137-144SIGLEAvailable from TIB Hannover: RR 8872(1999,1) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman