Is a crisis in pool boiling actually a hydrodynamic phenomenon?

Now many experimental facts are revealed, which contradict to the hydrodynamic theory of pool boiling crisis. Nevertheless, the majority of the latest modifications of boiling crisis model are based on the hydrodynamic approach; this makes actual the question submitted in the title of the paper. The well-known Kutateladze correlation for CHF was obtained on basis of dimensions analysis. This factually predetermines that any crisis model, which considers only hydrodynamic effects ignoring influence of liquid viscosity and heat transfer at the heated surface, inevitably leads to the Kutateladze equation with small corrections in the form of functions of liquid/vapor densities ratio. This is obviously seen from analysis of all theoretical models beginning from Zuber and till the newest ones. If in relation to the Kutateladze approach the main objection is the convincingly established fact that the limiting vapor velocity does not determine the crisis origin in the real boiling process and at low reduced pressures an actual vapor velocity can exceed the critical one many times, then in the theoretical studies always assumptions are found, which contradict to either experimental measurements or to some scientific fundamentals. However, at moderate and high reduced pressures the equation of the hydrodynamic model agrees satisfactorily with the data. Consequently, now it is necessary not only to develop a new approach to pool boiling crisis, but also to explain rather good predicting capability of the Kutateladze Zuber equation. The model developed by the present author presents an attempt to exceed the limits of the hydrodynamic approach. The crisis is a result of enlarging area of dry spots which are an intrinsic feature of nucleate boiling. Great difference of vapor specific volume at high and low reduced pressures makes it reasonable to derive separately the equations for CHF for these two cases. A simple interpolating formula allows calculating CHF at arbitrary pressure. The equation for high reduced pressures gives the calculated CHF values close to those computed on the formulas of the hydrodynamic theory. As the most part of the experimental data are obtained at moderate and high reduced pressures, this coincidence gives a possible explanation of agreement of the Kutateladze's formula with the data. A weak variation of liquid kinematic viscosity at saturation line allows concealing its actual influence on CHF. (C) 2014 Elsevier Ltd. All rights reserved.