Thermo-fluid-dynamics of inverse Leidenfrost levitation of small liquid/solid spheres over liquid pools

Abstract

The present study provides a detailed theoretical investigation of the thermo-fluid-dynamics of the inverse Leidenfrost levitation phenomenon of a microscale droplet/solid on a liquid pool, and also the conditions essential for solid/liquid spherical objects to levitate. The theoretical model is developed for the floating characteristic of liquid/solid objects based on the thermo-fluid-dynamics of the vapor film during the inverse Leidenfrost effect. A very small thickness of the vapor layer, approximately of the order of micrometers, formed between the object and liquid pool during levitation, and its variation with the angular position and time history is considered in contrast to previous works. The actual magnitude of the overlapping contact angle is estimated and also incorporated in the present study. The effects of various influencing parameters, like nondimensionalized sphere radius, contact angle, and density ratio, on the levitation possibility and dynamics, are analyzed. The model is validated against experimental observations of the inverse Leidenfrost phenomenon for water drop levitating on a nitrogen liquid pool, and the effects of droplet parameters on total levitation time and dynamics are noted to provide accurate predictions. The approach presented is noted to provide a more accurate estimate of inverse Leidenfrost levitation compared to previous reports.