Evaporation of a liquid film in a microchannel under the action of a co-current dry gas flow
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ORIGINAL ARTICLE
Evaporation of a liquid film in a microchannel under the action of a co-current dry gas flow V. V. Kuznetsov 1,2
&
E. Yu. Fominykh 1
Received: 28 February 2019 / Accepted: 28 October 2019 # Springer Nature B.V. 2020
Abstract A joint motion of thin liquid film and dry gas in a microchannel is investigated numerically at different values of initial concentration of the liquid vapor in the gas phase, taking into account the evaporation process. Major factors affecting the temperature distribution in the liquid and gas phases are as follows: transfer of heat by liquid and gas flows, heat loses due to evaporation, diffusion and heat transfer. The velocity and temperature fields in the liquid and gas phases, as well as the vapor concentration in the gas, were calculated. It has been established that in the zone of entry of flows into the channel near the interface, thermal and concentration boundary layers are formed, whose properties differ from the classical ones. Comparisons of the numerical results for the case of the dry gas and for the case of equilibrium concentration of vapor in the gas have been carried out. It is shown that use of dry gas enhances the heat dissipation from the heater. It is found out that not only intense evaporation occurs near the heating areas, but also in both cases vapor condensation takes place below the heater in streamwise direction. Keywords Shear-driven liquid film . Local heating . Thermocapillarity . Microgravity . Long-wave theory
Nomenclature A dimensionless number (g cos α H 20 =U 2 l ) b heat transfer coefficient, W/(m2 K) cp specific heat of the liquid, J/(kg K) B inverse Froude number (g sin α H0/U2) C mass fraction of moisture in the gas phase C* (T) mass fraction of moisture in the gas phase corresponding to the pressure of the saturated vapor at the temperature T C1 (t) mass fraction of moisture in the gas phase at the channel entry point of the flow D diffusion coefficient, m2/s E dimensionless number (f H 20 =μ0 U ) This article belongs to the Topical Collection: Thirty Years of Microgravity Research - A Topical Collection Dedicated to J. C. Legros Guest Editor: Valentina Shevtsova * V. V. Kuznetsov [email protected] 1
Lavrentyev Institute of Hydrodynamics, Russian Academy of Sciences, prosp. Lavrentyev 15, Novosibirsk 630090, Russia
2
Novosibirsk State University, 2 Pirogov str, Novosibirsk 630090, Russia
f F, G ! g h H HС H0 I k1, k2, k3 K l L Ma N ! n p P q Q R Re Ωn Sg T
the gas pressure gradient in the longitudinal direction, kg/(m2s2) Functions for intermediate calculations gravitational acceleration vector, m/s2 dimensionless film thickness local film thickness, m channel height, m film thickness at the initial moment identity tensor 3 dimensionless coefficients curvature of the interface, 1/m characteristic scale of streamwise length, m Evaporation number (λDρg/κ[T]) Marangoni number (σT ½T H 20 =U lμ0 ) modified Prandtl number (cpμ0H0/lκ) normal unit vector pressure, N/m2 stress tensors heat flux released on the heater, W/m2 flow
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