Interfacial thermal fluid phenomena in thin liquid films

Research output: Contribution to journalArticle

21 Citations (Scopus)

Abstract

Films are ubiquitous in nature and play an important role in our daily life. The paper focuses on the recent progress that has been achieved in the interfacial thermal fluid phenomena in thin liquid films and rivulets through conducting experiments and theory. Phase shift schlieren technique, fluorescence method and infrared thermography have been used. A spanwise regular structures formation was discovered for films falling down an inclined plate with a built-in local rectangular heater. If the heating is low enough, a stable 2D flow with a bump at the front edge of the heater is observed. For lager heat flux this primary flow becomes unstable, and the instability leads to another steady 3D flow, which looks like a regular structure with a periodically bent leading bump and an array of longitudinal rolls or rivulets descending from it downstream. The heat flux needed for the onset of instability grows almost linearly with the increase of Re number. Strong surface temperature gradients up to 10-15 K/mm, both in the streamwise and spanwise directions have been measured. For a wavy film it was found that heating may increase the wave amplitude because thermocapillary forces are directed from the valley to the crest of the wave. Thin and very thin (less than 10 μm) liquid films driven by a forced gas/vapor flow (stratified or annular flows), i.e. shear-driven liquid films in a narrow channel are a promising candidate for the thermal management of advanced semiconductor devices in earth and space applications. Development of such technology requires significant advances in fundamental research, since the stability of joint flow of locally heated liquid film and gas is a rather complex problem. Experiments with water and FC-72 in flat channels (height 0.2-2 mm) have been conducted. Maps of flow regimes were plotted. It was found that stratified flow exists and stable in the channels with 0.2 mm height and 40 mm width. The critical heat flux for a shear driven film may be up to 10 times higher than that for a falling liquid film, and reaches 400 W/cm2 in experiments with water at atmospheric pressure. Some experiments have been done during parabolic flight campaigns of the European Space Agency under microgravity conditions. It was found that decreasing of gravity leads to a flow destabilization.

Original languageEnglish
Pages (from-to)87-121
Number of pages35
JournalInternational Journal of Emerging Multidisciplinary Fluid Sciences
Volume2
Issue number2-3
DOIs
Publication statusPublished - 1 Jun 2010

Fingerprint

Liquid films
Thin films
Fluids
fluids
Heat flux
liquids
Gases
Experiments
stratified flow
heat flux
Heating
Beer
Water
Space applications
Microgravity
falling
heaters
Shear flow
Semiconductor devices
Phase shift

Keywords

  • critical heat flux
  • liquid films
  • thermocapillary effects

ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Fluid Flow and Transfer Processes

Cite this

Interfacial thermal fluid phenomena in thin liquid films. / Kabov, Oleg A.

In: International Journal of Emerging Multidisciplinary Fluid Sciences, Vol. 2, No. 2-3, 01.06.2010, p. 87-121.

Research output: Contribution to journalArticle

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