Local variation of frost layer thickness and morphology

This paper evaluates numerically some of the parameters involved in modeling the process of frost formation over a cold cylinder surface subject to the flow of humid air. Was utilized for numerical predictions the empirical Nusselt correlation from the literature, obtained in experimental studies on frost formation phenomena of frost grow over a cold cylinder surface. To predict frosting process a numerical solution was utilized, and a new correlation for Nusselt number based on the experimental correlation of Kim was estimated. For the new Nusselt correlation an optimization method that adjusts the numerical solution of modeling the frost formation process with experimental results of the frost layer thickness was used. The calculation procedure allows the estimation of the parameter K of equation. The modeling process was validated by comparison with available experimental data.

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Thermally Driven Shape Instability of Multilayer Structures

MRS Proceedings ◽

10.1557/proc-581-635 ◽

1999 ◽

Vol 581 ◽

Author(s):

P. Troche ◽

J. Hoffmann ◽

C. Herweg ◽

CH. Lang ◽

H.C. Freyhardt ◽

...

Keyword(s):

Layer Thickness ◽

Single Layer ◽

Local Variation ◽

Interfacial Stress ◽

Multilayer Systems ◽

Thermally Induced ◽

Transmission Electron ◽

Thermally Driven ◽

Interface Curvature ◽

Means Of Transmission

ABSTRACTThe thermally induced shape instability of Fe/Au, Fe/Ag, and Nb/Cu multilayer systems during heat treatments was investigated. The disintegration temperature of these systems decreases with decreasing single-layer thickness. Up to a critical thickness, the disintegration temperature is proportional to the reciprocal layer thickness. The driving force of this process is related to the interfacial stress and the local variation of the interface curvature. After heat treatment, spherically shaped Fe and Nb nanoparticles, located in chains perpendicular to the substrate, were observed and depicted by means of transmission electron microscopy (TEM) and X-ray microscopy (XRM).

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Experiment Study on Unsteady Frosting of Cryogenic Vertical Plate Surface under Natural Convection Conditions

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.516-517.24 ◽

2012 ◽

Vol 516-517 ◽

pp. 24-29 ◽

Cited By ~ 2

Author(s):

Shu Ping Chen ◽

Fu Shou Xie ◽

Shu Ting Yao ◽

Hong Yin Han ◽

Zhi Xin Chang

Keyword(s):

Natural Convection ◽

Vertical Plate ◽

Test Bench ◽

Tangential Direction ◽

Flow State ◽

Plate Surface ◽

Moist Air ◽

Working Medium ◽

Frost Layer Thickness ◽

Frost Layer

A frosting test bench was designed, and unsteady frosting on vertical plate surface was dynamically described with liquid nitrogen as working medium under natural convection conditions. The variation of frost thickness was analyzed, and the flow state of moist air and temperature distribution near the vertical plate were described. The experimental results show the unsteady frosting of vertical plate surface under natural convection and cryogenic condition actually includes several steps: formation of frost crystals, growth of frost crystals and growth of frost layer. The initial frosting rate is large, but the rate decreases as time goes on until the frost layer thickness is unchanged. Moist air conducts a top-down flow near the vertical plate, and the rest of moist air flows into the main flow. The temperature of moist air decreased systematically along the tangential direction of vertical plate from top to bottom and along the normal direction of vertical plate from far to vertical plate surface.

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Press and release imprint: Control of the flexible mold deformation and the local variation of residual layer thickness in soft UV-NIL

Microelectronic Engineering ◽

10.1016/j.mee.2011.01.073 ◽

2011 ◽

Vol 88 (6) ◽

pp. 1033-1036 ◽

Cited By ~ 11

Author(s):

Namil Koo ◽

Martin Otto ◽

Jung Wuk Kim ◽

Jun-Ho Jeong ◽

Heinrich Kurz

Keyword(s):

Layer Thickness ◽

Local Variation ◽

Residual Layer ◽

Mold Deformation ◽

Flexible Mold

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Hoar Frost Accretion on Organic Coatings Under Offshore Conditions

Journal of Offshore Mechanics and Arctic Engineering ◽

10.1115/1.4033931 ◽

2016 ◽

Vol 138 (6) ◽

Cited By ~ 1

Author(s):

A. W. Momber ◽

M. Irmer ◽

N. Glück

Keyword(s):

Uv Radiation ◽

Salt Spray ◽

Surface Parameter ◽

Test Scenario ◽

Specific Surface Energy ◽

Static Contact ◽

Frost Layer Thickness ◽

Corrosion Protection Coating ◽

Protection Coating ◽

Frost Layer

Nine organic corrosion protection coating systems are investigated according to their hoar frost accretion performance under simulated offshore conditions. A special test scenario is developed for the generation and measurement of defined hoar frost layers. Hoar frost layer thickness is estimated on newly applied coatings and on artificially aged coatings. The aging procedure refers to offshore conditions, which mainly cover low temperatures, dry–wet cycles, salt spray, and ultraviolet (UV) radiation. In average, the accreted thickness either did not change significantly or increased. Spearman's rank correlations were estimated for all surface parameters. If all measurements (new and aged) for an individual surface parameter were considered, only weak correlations were found between hoar frost thickness, static contact angle, specific surface energy, and surface roughness. The importance of UV radiation on the appearance of hoar frost is highlighted.

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Structure and Orientation of As Precipitates in LT-MBE Grown GaAs

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100088816 ◽

1991 ◽

Vol 49 ◽

pp. 900-901 ◽

Cited By ~ 1

Author(s):

Alain Claverie ◽

Zuzanna Liliental-Weber

Keyword(s):

Transport Properties ◽

Layer Thickness ◽

Growth Temperature ◽

Low Temperatures ◽

Lattice Parameter ◽

Crystalline Quality ◽

Insulating Properties ◽

Lt Gaas

GaAs layers grown by MBE at low temperatures (in the 200°C range, LT-GaAs) have been reported to have very interesting electronic and transport properties. Previous studies have shown that, before annealing, the crystalline quality of the layers is related to the growth temperature. Lowering the temperature or increasing the layer thickness generally results in some columnar polycrystalline growth. For the best “temperature-thickness” combinations, the layers may be very As rich (up to 1.25%) resulting in an up to 0.15% increase of the lattice parameter, consistent with the excess As. Only after annealing are the technologically important semi-insulating properties of these layers observed. When annealed in As atmosphere at about 600°C a decrease of the lattice parameter to the substrate value is observed. TEM studies show formation of precipitates which are supposed to be As related since the average As concentration remains almost unchanged upon annealing.

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The stabilization of B.C.C. Cu in Cu/Nb nanolayered composites

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100163605 ◽

1996 ◽

Vol 54 ◽

pp. 228-229

Author(s):

H. Kung ◽

A.J. Griffin ◽

Y.C. Lu ◽

K.E. Sickafus ◽

T.E. Mitchell ◽

...

Keyword(s):

Electrical Resistivity ◽

Layer Thickness ◽

Volume Fraction ◽

Ion Beam ◽

High Strength ◽

Cross Sectional ◽

Metastable Structure ◽

High Resolution Tem ◽

Potential Improvement ◽

Two Phases

Materials with compositionally modulated structures have gained much attention recently due to potential improvement in electrical, magnetic and mechanical properties. Specifically, Cu-Nb laminate systems have been extensively studied mainly due to the combination of high strength, and superior thermal and electrical conductivity that can be obtained and optimized for the different applications. The effect of layer thickness on the hardness, residual stress and electrical resistivity has been investigated. In general, increases in hardness and electrical resistivity have been observed with decreasing layer thickness. In addition, reduction in structural scale has caused the formation of a metastable structure which exhibits uniquely different properties. In this study, we report the formation of b.c.c. Cu in highly textured Cu/Nb nanolayers. A series of Cu/Nb nanolayered films, with alternating Cu and Nb layers, were prepared by dc magnetron sputtering onto Si {100} wafers. The nominal total thickness of each layered film was 1 μm. The layer thickness was varied between 1 nm and 500 nm with the volume fraction of the two phases kept constant at 50%. The deposition rates and film densities were determined through a combination of profilometry and ion beam analysis techniques. Cross-sectional transmission electron microscopy (XTEM) was used to examine the structure, phase and grain size distribution of the as-sputtered films. A JEOL 3000F high resolution TEM was used to characterize the microstructure.

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