Oleg A. Kabov

Experimental investigation of liquid drop evaporation on a heated solid surface

Evaporation of a water drop was studied experimentally at a temperature difference between the solid surface and surrounding atmosphere from 30 to 60 °C. The studies were performed on the substrates with micro- and nanocoatings with different wettability. The features of evaporation were studied for the pinned, partially pinned, and depinned three-phase contact line (solid-liquid−gas interface). It is shown that with a decrease in the water drop volume, the specific evaporation rate (mass flow per unit of surface area) increases, particularly at the last stage of evaporation.

Regimes of two-phase flow in micro- and minichannels (review)

The review deals with the analysis of the factors affecting the boundaries of two-phase regimes in the channels of different cross sections, whose minimal size is less than the capillary constant. The channels are classified by size. Data for two-phase flow regimes are systematized and summarized in tables for the round and rectangular tubes. It is indicated that the most studies identify the following two-phase flow regimes: bubble, slug and annular. The regimes found in some papers are described. The terminology used to describe the regimes is kept. Here we analyze the main factors affecting the structure of the two-phase flow, such as gas and liquid flow rates, parameters of the channel and input section, wettability of the inner surface of channels, liquid properties, and gravitational forces. It is shown that development of instability of the two-phase flow has a significant impact on formation, evolution, and change of the flow regimes.

Study of gas-water flow in horizontal rectangular channels

The two-phase flow in the narrow short horizontal rectangular channels 1 millimeter in height was studied experimentally. The features of formation of the two-phase flow were studied in detail. It is shown that with an increase in the channel width, the region of the churn and bubble regimes increases, compressing the area of the jet flow. The areas of the annular and stratified flow patterns vary insignificantly.

Study of dynamics of thin liquid layer breakdown under conditions of spot heating and formation of a droplet cluster

Breakdown dynamics was studied experimentally for the horizontal layers of various liquids (ethanol, water) with the thickness of 300 μm under the conditions of spot heating from the substrate. The main stages of the process of liquid layer breakdown were determined, and time of dry spot formation was measured. Time of dry spot formation for ethanol at the heat flux of 12.6 W/cm2 was 7.85 s, and for water at the heat flux of 117 W/cm2, it was 0.13 s. It was found that for both working liquids, a residual layer appears in the region of spot heating before liquid layer breakdown. It is shown that together with the thermocapillary effect, evaporation is one of the main factors affecting dynamics of liquid layer breakdown and dry spot formation.

Dry spot growth criterion for isothermal liquid films on a horizontal substrate

A criterion was elaborated for the phenomenon of dry spot evolution in isothermal liquid films on a horizontal substrate. The formulas are presented for gravity force and surface tension acting upon an element of the rim around the dry spot. The forces balance gives the evolution of initial dry spot: to expand or to contract.

Features of two-phase flow in a rectangular microchannel with the height of 300 μm

The two-phase flow in a narrow short horizontal channel of rectangular cross section with the width of 10 mm and height of 300 μm was studied experimentally. The features of the jet regime were studied in detail. It is shown that an increase in superficial velocity of jet pulsation frequency increases, and the ratio of unwetted area of the upper channel wall to the wetted area of the upper channel wall decreases.