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RESEARCH PAPERS: Evaporation, Boiling, and Condensation

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

[+] Author and Article Information
Sashidhar S. Panchamgam

 Micron Technology, Inc., Boise, ID 83707

Joel L. Plawsky

The Isermann Department of Chemical and Biological Engineering,  Rensselaer Polytechnic Institute, Troy, NY 12180

Peter C. Wayner1

The Isermann Department of Chemical and Biological Engineering,  Rensselaer Polytechnic Institute, Troy, NY 12180wayner@rpi.edu

1

Corresponding author.

J. Heat Transfer 129(11), 1476-1485 (Mar 18, 2007) (10 pages) doi:10.1115/1.2759970 History: Received July 07, 2006; Revised March 18, 2007

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.

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Copyright © 2007 by American Society of Mechanical Engineers
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Figures

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Figure 1

(a) Schematic of the experimental system (inside dimensions 3mm×3mm×43mm), (b) cross-sectional view (line AB in (a)) of the quartz cuvette. Gravity g is acting perpendicular to the square cross section.

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Figure 2

Reflectivity images illustrating the movement of the pentane and octane menisci due to change in the heater power: (a) isothermal pentane meniscus (t=2.86s), (b) nonisothermal (pseudosteady state) pentane meniscus (t=500s), (c) isothermal octane meniscus (t=1.21s), and (d) nonisothermal (pseudosteady state) octane meniscus (t=234.4s). Reflectivity images were captured at an axial location of x≈0 (near the heater).

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Figure 3

Illustration of the zeroth dark fringe movement due to change in the heater power. II′: Isothermal reference state, R-1: receding cycle, and A-1: advancing cycle.

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Figure 4

Comparison of profiles of the distance traveled as a function of time by (a) the pentane meniscus and (b) the octane meniscus

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Figure 5

Comparison of profiles of the velocity of the interference fringe at σ=0.1μm as a function of time of (a) the pentane meniscus and (b) the octane meniscus

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Figure 6

(a) Comparison of thickness profiles of the pentane meniscus at (i) isothermal state (t=2.86s), (ii) nonisothermal (pseudosteady) state (t=163.2s), and (b) expanded scale in the contact line region

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Figure 7

(a) Comparison of thickness profiles of the octane meniscus at (i) isothermal state (t=1.21s), (ii) nonisothermal (pseudosteady) state (t=234.4s) and (b) expanded scale in the contact line region

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Figure 8

Comparison of capillary pressure profiles of the pentane and octane menisci during (a) isothermal and (b) nonisothermal states

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Figure 9

(a) Isothermal octane meniscus on the quartz surface, (b) isothermal octane meniscus containing Pt nanoparticles (∼50nm) on the quartz surface, (c) reflectivity image of quartz surface containing Pt nanoparticles (∼50nm) after complete dryout, and (d) comparison of thickness profiles of the octane meniscus and octane meniscus containing Pt nanoparticles during isothermal state in the contact line region (26)

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Figure 10

Comparison of adsorbed film thickness profiles as a function of time of (a) the pentane meniscus and (b) the octane meniscus

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Figure 11

Comparison of profiles of the slope angle at δ=0.1μm as a function of time of (a) the pentane meniscus and (b) the octane meniscus

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Figure 12

Comparison of disjoining pressure profiles of the pentane and octane menisci during (a) isothermal and (b) nonisothermal states

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Figure 13

Comparison of liquid pressure profiles of the pentane and octane menisci during nonisothermal state

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Figure 14

Variation in the surface tension (σ) and the change in mole fraction of nonane (Δx2) with the length of the octane meniscus during nonisothermal (pseudosteady) state for the stationary meniscus condition

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