This paper deals with investigation results on boiling up and crisis phenomena for nonstationary heat release in falling liquid films. According to the experimental results, in the studied range of irrigation degree alteration (Re_(in) = 50 — 1300), parameters, characterizing decay of the falling liquid film with stepped heat release (distribution of time of boiling incipience along the liquid film, velocities of movable boundaries in the boiling-up and drying fronts), depend complexly on the Reynolds number, wave characteristics and heat flux density. Experiments were carried out with the use liquid nitrogen. Step-wise heat release was supplied on the vertical plane constantan foil of the 25-mkm thickness and 40-mm length. When loading impulses of high intensity, film decay is determined by dynamic characteristics of propagation of the self-maintained fronts of evaporation and the complex shape of structures, formed during its development. The effect of heat flux density on the time of boiling-up expectation and structures of evaporation fronts is shown for different Reynolds numbers. The experimental data obtained on the average propagation velocity of the self-maintained front of evaporation are compared with the simulation model results.
展开▼
