MODELING THE CAPILLARY INFLOW OF A LIQUID TO DRY SPOTS ABOVE VAPOR BUBBLES AS A FACTOR OF INCREASING THE CRITICAL HEAT-FLUX DENSITY DURING THE BOILING ON A POROUS SURFACE

The authors propose a calculation model for the process of infl ow of a liquid from a microfi lm to dry spots above vapor bubbles, which occurs in nucleate boiling and is due to the action of capillary forces (Laplace head) in a porous coating on the heating surface. In comparing the value of the heat fl ux from the heating surface to the interface in the zone of intense evaporation of the liquid and the value of the heat fl ux to evaporate the liquid sucked through a porous substrate to a dry spot, it turns out that these values are comparable, which explains the effect of rise in the critical density of the heat fl ux on porous surfaces compared to "smooth" surfaces. A comparison of the results of quantifi cation of this effect with the proposed model and the experimental data obtained during the boiling of water on a porous surface that was formed by nanoparticles precipitated from a nanolfl uid has shown their mutual agreement
   
Author:  E. D. Fedorovich ,  A. N. Kovalenko ,  S. S. Makukhin
Keywords:  nucleate boiling, active nucleation site, vapor bubble, microfi lm, dry spot, critical heat-fl ux density, porous coating, capillary-infl ow effect
Page:  473