Nano-scale transport characteristics during thin film evaporation: Effect of liquid film thickness

2018 ◽  
Author(s):  
Chandni Akhter ◽  
Renoa Choudhury ◽  
Fatama Tahsin Huda ◽  
Mohammad Nasim Hasan
Keyword(s):  
Thin Film ◽  
Film Thickness ◽  
Liquid Film ◽  
Liquid Film Thickness ◽  
Thin Film Evaporation ◽  
Film Evaporation ◽  
Nano Scale

Numerical study of falling binary liquid film evaporation: liquid film thickness

2017 ◽  
Vol 74 ◽  
pp. 35-43
Author(s):  
Abdelaziz Nasr ◽  
Abdulmajeed S. Al-Ghamdi ◽  
M’barek Feddaoui ◽  
Mohammad S. Alsoufi ◽  
Sassi Ben Nasrallah
Keyword(s):  
Film Thickness ◽  
Liquid Film ◽  
Numerical Study ◽  
Liquid Film Thickness ◽  
Film Evaporation ◽  
Binary Liquid

High-Flux Thin Film Evaporation on Nanostructured Surfaces

2010 ◽  
Author(s):  
Rong Xiao ◽  
Kuang-Han Chu ◽  
Evelyn N. Wang
Keyword(s):  
Thin Film ◽  
Liquid Film ◽  
High Performance ◽  
Heat Dissipation ◽  
Heat Removal ◽  
High Heat ◽  
Back Side ◽  
Nanostructured Surfaces ◽  
Thin Film Evaporation ◽  
Film Evaporation

The heat generation rates of high performance electronics motivate the development of new thermal management solutions. Thin film evaporation with a jet impingement or spray system promise high heat fluxes up to 1000 W/cm2 with low thermal resistances. However, challenges with implementation currently limit the ability to reach the theoretical limits. In this work, we investigated the utilization of micro-/nanostructured surfaces to control the liquid film thickness and provide a sufficient liquid flow rate to achieve high heat removal rates. We developed a model to predict the propagation rates of the liquid film, which accounted for the curvature of the liquid meniscus. We also fabricated test devices with pillar diameters ranging from 500 nm to 10 μm, spacings of 3.5 μm to 10 μm, and heights of 5 μm to 15 μm, and validated the model with confocal microscopy and high speed imaging. Heaters and temperature sensors were also integrated onto the back side of the chip to investigate heat transfer performance. When heat was applied, the structures significantly enhanced the heat dissipation rates and reduced the thermal resistance. The heat dissipation rate was also found to be positively correlated to the propagation rate of the liquid film. However, surface fouling in the experiments led to challenges to maintain a stable liquid film, and decreased the heat removal capability. This work provides insights to designing micro-/nanostructured surfaces for thin film evaporation to meet the heat dissipation demands of future high performance electronic systems.

Falling Films in Micro- and Minigrooves: Heat Transfer and Flow Stability

2003 ◽  
Author(s):  
Tatiana Gambaryan-Roisman ◽  
Peter Stephan
Keyword(s):  
Thin Film ◽  
Heat Transfer ◽  
Liquid Film ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Film Flow ◽  
Wall Structure ◽  
Falling Film ◽  
Thin Film Evaporation ◽  
Film Evaporation

Structured (in particular, micro- and minigrooved) wall surfaces may improve numerous industrial processes, including falling film evaporation, thin film evaporation in lean premixed prevaporized combustion technology (LPP), and spray and jet cooling. The advantages of such surfaces include the promotion of ultra-thin film evaporation at the apparent contact lines and the prevention of dry patches on hot surfaces. However, the behavior of thin film flow on structured surfaces has not yet been comprehensively studied. We derive a model describing the heat transfer in liquid film flowing down inclined micro- or minigrooved walls. The derived model accounts for peculiarities of the evaporation process in the vicinity of the liquid-vapor-solid contact line (“micro region”) and their effect on the overall heat transfer rate. It is shown that the effect of the micro region is to increase the overall heat transfer rate at the constant fluid flow rate. A long-wave stability analysis has been performed to quantify the effect of the capillary structure on the film stability properties. Sinusoidal and triangular longitudinal groove shapes have been considered. Two cases have been studied: (i) the film completely covers the wall structure; (ii) the film partly covers the wall structure. It is shown that the longitudinal grooves completely covered by the liquid have a stabilizing effect on the falling film flow. The performed analysis is a step towards modeling the wavy motion of the liquid film on grooved surfaces.

Surface Temperatures and Heat Fluxes Associated With the Evaporation of a Liquid Film on a Semi-Infinite Solid

1971 ◽  
Vol 93 (4) ◽  
pp. 357-364 ◽  
Author(s):  
L. A. Hale ◽  
S. A. Anderson
Keyword(s):  
Thin Film ◽  
Boundary Value Problem ◽  
Liquid Film ◽  
Numerical Solution ◽  
Thin Liquid Film ◽  
Pool Boiling ◽  
Heat Fluxes ◽  
Thin Film Evaporation ◽  
Film Evaporation ◽  
Limiting Case

The boundary-value problem associated with the evaporation of a thin liquid film from a thick surface is presented in terms of several dimensionless parameters. A numerical solution is presented for a particular limiting case and the result is used to suggest criteria for determining the significance of thin-film evaporation in saturated pool boiling.

Characteristics of Extended Evaporating Meniscus on Nanotextured Rough Solid Substrate for Wenzel States

2011 ◽  
Author(s):  
J. J. Zhao ◽  
Y. Y. Duan ◽  
X. D. Wang ◽  
B. X. Wang
Keyword(s):  
Thin Film ◽  
Heat Transfer ◽  
Liquid Film ◽  
Thin Liquid Film ◽  
Disjoining Pressure ◽  
Roughness Effects ◽  
Maximum Heat ◽  
Thin Film Evaporation ◽  
Film Evaporation ◽  
Nanoscale Roughness

The surface nanostructure determines the system wettability and thus has significant effects on the thin liquid film spreading and phase change heat transfer. A model based on the augmented Young-Laplace equation and kinetic theory was developed to describe the nanoscale roughness effects on the extended evaporating meniscus in a microchannel. The roughness geometries in the model were theoretically related to the disjoining pressure and the thermal resistance across the roughness layer. The results show that the dispersion constant for the disjoining pressure increases with the nanopillar height when the solid-liquid-vapor system is in the Wenzel state. Thus, the spreading and wetting properties of the evaporating thin liquid film are enhanced due to the higher nanopillar height and larger disjoining pressure. Since the evaporating thin film length increases with the nanoscale roughness due to better surface wettability, the total liquid flow and heat transfer rate of the evaporating thin liquid films in a microchannel can be enhanced by increasing the nanopillar height. The effects of the nanopillar on the thin film evaporation are more significant for higher superheats. Hydrophilic nanotextured solid substrates can be fabricated to enhance the thin film evaporation and thus increase the maximum heat transport capability of the two-phase cooling devices.

scholarly journals Improving oxidation efficiency through plasma coupled thin film processing

RSC Advances ◽  
2017 ◽  
Vol 7 (74) ◽  
pp. 47111-47115 ◽  
Author(s):  
Darryl B. Jones ◽  
Colin L. Raston
Keyword(s):  
Thin Film ◽  
Film Thickness ◽  
Liquid Film ◽  
Liquid Film Thickness ◽  
Processing Efficiency ◽  
Film Processing ◽  
Oxidation Efficiency ◽  
Thin Film Processing

Plasma liquid processing efficiency improves by reducing the liquid film thickness.

Controlled Wetting in Nanoporous Membranes for Thin Film Evaporation

2016 ◽  
Vol 138 (8) ◽  
Author(s):  
Kyle L. Wilke ◽  
Banafsheh Barabadi ◽  
TieJun Zhang ◽  
Evelyn N. Wang
Keyword(s):  
Thin Film ◽  
Liquid Film ◽  
Membrane Surface ◽  
High Heat ◽  
Nanoporous Membranes ◽  
Transfer Rates ◽  
Thin Film Evaporation ◽  
Film Evaporation ◽  
High Heat Transfer ◽  
Controlled Flooding

With the ever increasing cooling demands of advanced electronics, thin film evaporation has emerged as one of the most promising thermal management solutions. High heat transfer rates can be achieved in thin films of liquids due to a small conduction resistance through the film to the evaporating interface. In thin film evaporation, maintaining a stable liquid film to attain high evaporation rates is challenging. We investigated nanoporous anodic aluminum oxide (AAO) membranes to supply liquid to the evaporating surface via capillarity. In this work, we achieved enhanced experimental control via the creation of a hydrophobic section within the nanopore. By creating a non-wetting section, the liquid is confined within the membrane to a region of well-controlled geometry. This non-wetting section also prevents flooding, where the formation of a thick liquid film degrades device performance. When heat flux is applied to the membrane surface, the liquid wicks into the membrane from the bottom and becomes pinned at the onset of the hydrophobic layer. As a result, the wetting in the membrane is controlled, flooding is prevented, and a stable evaporating surface in achieved. With this approach, thin film evaporation from nanoporous media can now be studied for varying parameters such as pore size, porosity, and location of the meniscus within the pore.

Microengineered Surfaces for Thin Film Evaporation for Enhanced Heat Dissipation

2009 ◽  
Author(s):  
Rong Xiao ◽  
Evelyn N. Wang
Keyword(s):  
Thin Film ◽  
Liquid Film ◽  
Thermal Management ◽  
Heat Dissipation ◽  
Thin Liquid Film ◽  
High Heat ◽  
Heat Fluxes ◽  
Thin Film Evaporation ◽  
Film Evaporation ◽  
Micropillar Arrays

The increasing performance of integrated chips has introduced a growing demand for new thermal management technologies. While various thermal management schemes have been studied, thin film evaporation promises high heat dissipation rates (1000 W/cm2) with low thermal resistances. However, methods to form a thin liquid film including jet impingement and sprays have challenges associated with achieving the desired film thickness. In this work, we investigated novel microstructures to control the thickness of the thin film where the liquid is driven by capillarity. Micropillar arrays with diameters ranging from 2 μm to 10 μm, spacings between pillars ranging from 5 μm to 10 μm, and heights of 4.36 μm were studied. A semi-analytical model was developed to predict the propagation rate of the liquid film, which was validated with experiments. The heat transfer performance was investigated on the micropillar arrays with microfabricated heaters and temperature sensors. The behavior of the thin liquid film under varying heat fluxes was studied. This work demonstrates the potential of micro- and nanostructures to dissipate high heat fluxes via thin film evaporation.

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