Vyacheslav Cheverda

Two-phase flow in short rectangular mini-channel

Recent developments in electronics and medicine generate an interest in capillary hydrodynamics and heat transfer in Microsystems. Microsystems also are very important for aerospace industry. In the present paper we focus upon experiments in the short channel oriented horizontally with the width 40 mm, height 1 mm and length 80 mm. New flow regimes are observed and the two-phase flow pattern map is created. The obtained results are compared with the data available in the literature.

Rivulet Flows in Microchannels and Minichannels

Thin liquid films or rivulets may provide very high heat transfer intensity, especially in the micro region near contact-line and may be used for cooling of microelectronic equipment or engines. The paper focuses on the recent progress that has been achieved in the understanding of the rivulet flow phenomena in micro/mini-channels through conducting experiments and theory. Experiments on a gas shear-driven rivulet flow in a minichannel have been done during four parabolic flights campaigns of the European Space Agency. The phase shift schlieren technique and a conventional schlieren technique have been used for two-phase flow visualization. The force balance is varied during a parabolic flight and due to surface tension effect the liquid film in a minichannel 40 mm width became a flattened rivulet 9 mm width at microgravity. The rivulet reaches the certain equilibrium width at microgravity. The numerical calculations of the flow depending on the gravity forces have been made. It was found also that the ri...

The Effect of Fluid Properties on Two-Phase Regimes of Flow in a Wide Rectangular Microchannel

We have experimentally studied a two-phase flow in a microchannel with a height of 150 μm and a width of 20 mm. Different liquids have been used, namely, a purified Milli-Q water, an 50% aqueous-ethanol solution, and FC-72. Before and after the experiment, the height of the microchannel was controlled, as well as the wettability of its walls and surface tension of liquids. Using the schlieren method, the main characteristics of two-phase flow in wide ranges of gas- and liquid-flow rates have been revealed. The flow regime-formation mechanism has been found to depend on the properties of the liquid used. The flow regime has been registered when the droplets moving along the microchannel are vertical liquid bridges. It has been shown that, when using FC-72 liquid, a film of liquid is formed on the upper channel wall in the whole range of gas- and liquid-flow rates.