Microscale Temperature Measurements Near the Contact Line of an Evaporating Thin Film in a V-Groove

2009 ◽  
Author(s):  
C. P. Migliaccio ◽  
H. K. Dhavaleswarapu ◽  
S. V. Garimella
Keyword(s):  
Thin Film ◽  
Contact Line ◽  
Quartz Substrate ◽  
Constant Heat Flux ◽  
Electrical Heating ◽  
Thin Film Evaporation ◽  
Meniscus Shape ◽  
Liquid Feeding ◽  
Line Region ◽  
Balance Analysis

Thin-film evaporation of heptane in a V-groove geometry is experimentally investigated. The groove is made of fused quartz, and electrical heating of a thin layer of titanium coated on the backside of the quartz substrate provides a constant heat flux. The effects of liquid feeding rate on the temperature suppression in the thin-film region and on the meniscus shape are explored. High resolution (∼6.3 μm) infrared thermography is employed to investigate the temperature profile in the thin-film region, while a goniometer is used to image the meniscus shape. An approximate heat balance analysis is used to estimate the fraction of total meniscus heat transfer which takes place in the contact line region.

Use of Scanning Microphotometer to Determine the Evaporative Heat Transfer Characteristics of the Contact Line Region

1981 ◽  
Vol 103 (2) ◽  
pp. 325-330 ◽  
Author(s):  
R. Cook ◽  
C. Y. Tung ◽  
P. C. Wayner
Keyword(s):  
Thin Film ◽  
Heat Transfer ◽  
Heat Flux ◽  
Contact Line ◽  
Heat Transfer Characteristics ◽  
Thin Film Thickness ◽  
Thickness Profile ◽  
Line Region ◽  
Evaporative Heat Transfer

A scanning microphotometer was used to measure in situ the profile of an evaporating decane meniscus in the contact line region on a smooth inclined silicon substrate as a function of the evaporative heat flux. The use of this new experimental design to determine the effect of heat flux on the profile in the contact line region is discussed. The results support the hypothesis that fluid flow in the contact line region of an evaporating thin film results from a change in the thin film thickness profile.

A Study of an Oscillating Corner Meniscus With Phase Change Using Image Analyzing Interferometry

Volume 4 ◽  
2004 ◽  
Author(s):  
Sashidhar S. Panchamgam ◽  
Shripad J. Gokhale ◽  
Joel L. Plawsky ◽  
Sunando DasGupta ◽  
Peter C. Wayner
Keyword(s):  
Fluid Flow ◽  
Phase Change ◽  
Contact Line ◽  
Quartz Substrate ◽  
Thin Liquid Film ◽  
Adsorbed Film ◽  
Line Region ◽  
The Stability ◽  
First Time

The thickness and curvature profiles in the contact line region of a moving evaporating thin liquid film of pentane on a quartz substrate were measured for the thickness region, δ < 2.5 microns. The critical region, δ < 0.1 microns, was emphasized. The profiles were obtained using image analyzing interferometry and an improved data analysis procedure. The precursor adsorbed film, the thickness, the curvature, and interfacial slope (variation of the local “apparent contact angle”) profiles were consistent with previous models based on interfacial concepts. Isothermal equilibrium conditions were used to evaluate the Hamaker constant in-situ and to verify the accuracy of the procedures. The profiles give fundamental insights into the phenomena of phase change, pressure gradient, fluid flow, spreading, and the physics of interfacial phenomena in the contact line region. The experimental results demonstrate explicitly for the first time, with microscopic detail, that the disjoining pressure controls fluid flow within an evaporating completely wetting thin curved film and the stability of the thin film. The change in the thickness of the adsorbed film with time is demonstrated for the first time.

Microscale Temperature Measurements at the Triple Line of an Evaporating Thin Film

2007 ◽  
Author(s):  
Hemanth K. Dhavaleswarapu ◽  
Suresh V. Garimella ◽  
Jayathi Y. Murthy
Keyword(s):  
Thin Film ◽  
Quartz Substrate ◽  
Infrared Camera ◽  
Triple Line ◽  
Temperature Measurements ◽  
Confined Space ◽  
Two Phase ◽  
Thin Film Evaporation ◽  
Film Heat Transfer ◽  
Two Phase Cooling

Thin-film evaporation from a meniscus in a confined space, which is the basis for many two-phase cooling devices, is experimentally investigated. The meniscus formed by heptane, a highly wetting liquid, on a heated, fused quartz substrate is studied. Microscale infrared temperature measurements performed near the thin-film region of the evaporating meniscus reveal the temperature suppression caused by the intensive evaporation in this region. The high spatial resolution (∼6.3 μm) and high temperature sensitivity (∼20 mK) of the infrared camera allowed for accurate measurements. The effects of meniscus thickness and applied heat flux on the thin-film heat transfer distribution and rate are also explored.

Heat Transfer During Evaporation and Boiling at the Three Phase Contact Line Region: A Critical Review

2015 ◽  
Author(s):  
Pruthvik A. Raghupathi ◽  
Satish G. Kandlikar
Keyword(s):  
Heat Transfer ◽  
Contact Line ◽  
Measurement Techniques ◽  
Nucleate Boiling ◽  
Analytical Models ◽  
Thin Film Evaporation ◽  
Line Region ◽  
Three Phase ◽  
Comprehensive Picture ◽  
Transfer Behavior

A fundamental understanding of the various modes of heat transfer and their contributions is critical in the development of enhanced surfaces to augment boiling performance. Recently, a number of studies have highlighted the importance of contact line region in boiling-especially in applications involving thin film evaporation and wicking structures. Contact line region also plays an important role during heat transfer around a nucleating bubble, especially at higher bubble frequencies near critical heat flux (CHF). In this work, a review of the characteristics of the contact line region, the forces at play, and the associated heat transfer mechanisms is conducted. Experimental and analytical works on the contact line region are explored to develop a comprehensive picture of its physical and heat transfer behavior. Various optical and thermal measurement techniques employed by researchers to understand evaporation in the contact line region are also reviewed. The interaction of different forces in this region and the analytical models for predicting the forces is studied. Finally, the contribution of microlayer and contact line heat transfer in nucleate boiling is also presented.

Experimental Evaluation of Marangoni Shear in the Contact Line Region of an Evaporating 99+% Pure Octane Meniscus

2007 ◽  
Vol 129 (11) ◽  
pp. 1476-1485 ◽  
Author(s):  
Sashidhar S. Panchamgam ◽  
Joel L. Plawsky ◽  
Peter C. Wayner
Keyword(s):  
Thin Film ◽  
Fluid Flow ◽  
Intermolecular Interactions ◽  
Contact Line ◽  
Disjoining Pressure ◽  
Operating Conditions ◽  
Working Fluid ◽  
Quartz Surface ◽  
Experimental Conditions ◽  
Line Region

Image analyzing interferometry was used to study the spreading characteristics of an evaporating octane meniscus (purity: 99+%) on a quartz surface. The thickness, slope, and curvature profiles in the contact line region of the meniscus were obtained using a microscopic data analysis procedure. The results obtained for the octane were compared to that of pure pentane (purity: >99.8%) under similar operating conditions. Isothermal experimental conditions of the menisci were used for the in situ estimation of the retarded dispersion constant. The experimental results for the pure pentane demonstrate that the disjoining pressure (the intermolecular interactions) in the thin-film region controls the fluid flow. Also, an imbalance between the disjoining pressure in the thin-film region and the capillary pressure in the thicker meniscus region resulted in a creeping evaporating pentane meniscus, which spreads over the solid (quartz) surface. On the contrary, for less pure octane, the intermolecular interactions between octane and quartz had a significantly different contribution for fluid flow, and hence, the octane meniscus of lower purity did not creep over the quartz surface. As a result, we had a stationary, evaporating octane meniscus. Using the experimental data and a simple model for the velocity distribution, we evaluated the Marangoni shear in a portion of the stationary, evaporating octane meniscus. An extremely small change in the concentration due to distillation had a significant effect on fluid flow and microscale heat transfer. Also, it was found that nonidealities in small interfacial systems, i.e., the presence of impurities in the working fluid, can have a significant effect on the thickness of the adsorbed film, the heat flux, the spreading characteristics of an almost pure fluid, and, therefore, the assumptions in modeling.

Experimental Determination of the Effect of Disjoining Pressure on Shear in the Contact Line Region of a Moving Evaporating Thin Film

2005 ◽  
Vol 127 (3) ◽  
pp. 231-243 ◽  
Author(s):  
Sashidhar S. Panchamgam ◽  
Shripad J. Gokhale ◽  
Joel L. Plawsky ◽  
Sunando DasGupta ◽  
Peter C. Wayner,
Keyword(s):  
Fluid Flow ◽  
Contact Line ◽  
Quartz Substrate ◽  
Thin Liquid Film ◽  
Disjoining Pressure ◽  
Dispersion Constant ◽  
Line Region ◽  
Fundamental Insight ◽  
First Time

The thickness and curvature profiles in the contact line region of a moving evaporating thin liquid film of pentane on a quartz substrate were measured for the thickness region, δ<2.5 μm. The critical region, δ<0.1 μm, was emphasized. The profiles were obtained using image-analyzing interferometry and an improved data analysis procedure. The precursor adsorbed film, the thickness, the curvature, and interfacial slope (variation of the local “apparent contact angle”) profiles were consistent with previous models based on interfacial concepts. Isothermal equilibrium conditions were used to verify the accuracy of the procedures and to evaluate the retarded dispersion constant in situ. The profiles give fundamental insight into the phenomena of phase change, pressure gradient, fluid flow, spreading, shear stress, and the physics of interfacial phenomena in the contact line region. The experimental results demonstrate explicitly, for the first time with microscopic detail, that the disjoining pressure controls fluid flow within an evaporating completely wetting thin curved film.

Numerical investigation of the dynamic influence of the contact line region on the macroscopic meniscus shape

1996 ◽  
Vol 329 ◽  
pp. 137-146 ◽  
Author(s):  
Ivan B. Bazhlekov ◽  
Allan K. Chesters
Keyword(s):  
Contact Line ◽  
Stokes Equations ◽  
Capillary Tube ◽  
Creeping Flow ◽  
Navier Stokes ◽  
Initial Shape ◽  
Navier Stokes Equations ◽  
Meniscus Shape ◽  
Line Region ◽  
Flow Approximation

The influence of different boundary conditions applied in the contact line region on the outer meniscus shape is analysed by means of a finite-element numerical simulation of the steady movement of a liquid-gas meniscus in a capillary tube. The free-surface steady shape is obtained by solving the unsteady creeping-flow approximation of the Navier–Stokes equations starting from some initial shape. Comparisons of the outer solutions obtained using two different inner models, together with that published by Lowndes (1980), indicate the relative insensitivity of the outer solution to the type of model utilized in the contact line region.

Experimental Evaluation of Marangoni Shear in the Contact Line Region of an Evaporating 99+ % Pure Octane Meniscus

2006 ◽  
Author(s):  
Sashidhar S. Panchamgam ◽  
Joel L. Plawsky ◽  
Peter C. Wayner
Keyword(s):  
Thin Film ◽  
Fluid Flow ◽  
Intermolecular Interactions ◽  
Contact Line ◽  
Disjoining Pressure ◽  
Operating Conditions ◽  
Working Fluid ◽  
Quartz Surface ◽  
Experimental Conditions ◽  
Line Region

Image analyzing interferometry was used to study the spreading characteristics of an evaporating meniscus containing octane (purity: 99+ %) on a quartz surface. The thickness and curvature profiles in the contact line region of the meniscus were obtained using a microscopic data analysis procedure. The results obtained for the octane were compared with that of pure pentane under similar operating conditions. Isothermal experimental conditions of the meniscus were used for the in-situ estimation of the retarded dispersion constant. The experimental results for the pure pentane demonstrate that the disjoining pressure (the intermolecular interactions) in the thin film region controls the fluid flow. Also, an imbalance between the disjoining pressure in the thin film region and the capillary pressure in the thicker meniscus region resulted in a creeping evaporating pentane meniscus, which spread over the solid (quartz) surface. On the contrary, for less pure octane, the intermolecular interactions between octane and quartz had a significantly different contribution for fluid flow and hence the octane meniscus of lower purity did not creep over the quartz surface. As a result, we had a stationary, evaporating octane meniscus. Using the experimental data and a simple model for velocity distribution, we evaluated the Marangoni shear in a portion of the stationary, evaporating octane meniscus. An extremely small change in the concentration due to distillation had a significant effect on fluid flow and microscale heat transfer. Also, it was found that non-idealities in small interfacial systems, i.e. the presence of impurities in the working fluid, can have a significant effect on the thickness of the adsorbed film and therefore the spreading characteristics of an almost pure octane meniscus.

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