Thermocapillary effects in nonisothermal liquid film at high Reynolds numbers

Chinnov, E. A.

doi:10.1134/s0018151x13020041

Cited by 5 publications

(1 citation statement)

References 18 publications

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“…Using these parameters, taking into account the environmental parameters: temperature (°C), relative humidity (%) and atmospheric pressure (Pa), we calculated the average coefficients by the height of the surface: heat transfer coefficient In the course of the experiments, it was found that the width of the film flowing down the heated surface decreases with increasing distance from its initial section, while the flowing down along the unheated surface, it remains constant. This phenomenon can be explained by the thermocapillary effect arising as a result of intense evaporation of the liquid in the region of the "liquidvapor -wall" contact line, which leads to a change in the curvature of the interphase surface [13,14]. It requires a separate study, therefore, in this work, reduced film widths, which in many cases reached 50 %, were taken into account for each experiment by measuring the film width by the height of the working surface, followed by recalculation through the film surface area to its average width b (m).…”

Section: Description Of the Experimental Setup And Experimentsmentioning

confidence: 99%

An Experimental Study of Heat and Mass Transfer in a Falling Liquid Film Evaporation into a Crossflow of Neutral Gas

Lukashov

Кostiuchenko

Timofeev

et al. 2020

JES

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The work is devoted to the study of heat and mass transfer in a liquid film flowing down on a heated surface under conditions of evaporation into a crossflow of a gas neutral with respect to the liquid. The work aimed to experimentally determine the average heat transfer coefficients from a heated surface to the film, heat transfer and mass transfer from the film to the gas flow and to establish their dependence on the input parameters of the heat and mass transfer process. To achieve this goal, an experimental setup was created, and a research technique was developed based on the proposed mathematical model of the heat and mass transfer process. The results of the study showed that the dependences of the average heat and mass transfer coefficients on the initial liquid flow rate are extreme with the minimum values of these coefficients at the liquid flow rate, which corresponds to the critical value of the Reynolds criterion Re l cr ≈ 500, which indicates a transition from the laminar falling films to turbulent mode under the considered conditions. The dependences of the heat and mass transfer coefficients on other process parameters for both modes of film falling are established. A generalization of the experimental data made it possible to obtain empirical equations for calculating these coefficients. Keywords: heat and mass transfer, cross flow, film apparatus, heat and mass return coefficient, neutral gas.

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Section: Description Of the Experimental Setup And Experimentsmentioning

confidence: 99%

An Experimental Study of Heat and Mass Transfer in a Falling Liquid Film Evaporation into a Crossflow of Neutral Gas

Lukashov

Кostiuchenko

Timofeev

et al. 2020

JES

View full text Add to dashboard Cite

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Linear stability analysis of thin liquid film flow over a heterogeneously heated substrate

2014

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The linear stability of a thin film of volatile liquid flowing over a surface with embedded, regularly spaced heaters is investigated. The temperature gradients at the upstream edges of the heaters induce gradients in surface tension that create a pronounced non-uniformity in the film profile due to the formation of capillary ridges. The Governing equations for the evolution of the film thickness are derived within the lubrication approximation, and three important parameters that affect the dynamics and stability of the film are identified. The computed two-dimensional, steady solutions for the local film thickness reveal that due to evaporation there is a slight change in the height of capillary ridge at subsequent heaters downstream. Using a linear stability analysis, it is shown that, as for a single heater, the film is susceptible to two types of instabilities. A rivulet instability leads to spanwise-periodic rivulets, and an oscillating thermocapillary instability leads to streamwise, time-periodic oscillations in the film thickness. The critical Marangoni number is calculated for both types of instability for a range of parameter values. The effect of the number of heaters, heater width, and gap between the heaters on the critical Marangoni number is computed and analyzed. For small evaporation rates and less volatile films, the presence of multiple heaters has almost no noticeable effect on the film stability. For larger evaporation rates and more volatile films, additional heaters decrease the Marangoni number at instability onset. The destabilizing effect of multiple heaters is sensitive to the heater geometry and spacing. Furthermore, the limitations of streamwise periodic boundary conditions for analyzing the stability of such flows are discussed. Computations on the transient and nonlinear growth of perturbations are also presented and indicate that the results of eigenanalysis are physically determinant.

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