Temperature Jump Coefficient for Superhydrophobic Surfaces

2014 ◽  
Vol 136 (6) ◽  
Author(s):  
Chiu-On Ng ◽  
C. Y. Wang
Keyword(s):  
Thermal Conductivity ◽  
Heat Conduction ◽  
Superhydrophobic Surface ◽  
Temperature Jump ◽  
Velocity Slip ◽  
Creeping Flow ◽  
Superhydrophobic Surfaces ◽  
Constant Ratio ◽  
Interfacial Temperature ◽  
Temperature Jump Coefficient

Mathematical models are developed for heat conduction in creeping flow of a liquid over a microstructured superhydrophobic surface, where because of hydrophobicity, a gas is trapped in the cavities of the microstructure. As gas is much lower in thermal conductivity than liquid, an interfacial temperature slip between the liquid and the surface will develop on the macroscale. In this note, the temperature jump coefficient is numerically determined for several types of superhydrophobic surfaces: a surface with parallel grooves, and surfaces with two-dimensionally distributed patches corresponding to the top of circular or square posts, and circular or square holes. These temperature jump coefficients are found to have a nearly constant ratio with the corresponding velocity slip lengths.

scholarly journals Lattice Boltzmann method simulation of the gas heat conduction of nanoporous material

2020 ◽  
Vol 24 (6 Part A) ◽  
pp. 3749-3756
Author(s):  
Ya Han ◽  
Shuai Li ◽  
Hai-Dong Liu ◽  
Weipeng Cui
Keyword(s):  
Thermal Conductivity ◽  
Heat Conduction ◽  
Lattice Boltzmann Method ◽  
Knudsen Number ◽  
Lattice Boltzmann ◽  
Size Effects ◽  
Temperature Jump ◽  
Boundary Scattering ◽  
Nanoporous Material ◽  
Boltzmann Method

In order to deeply investigate the gas heat conduction of nanoporous aerogel, a model of gas heat conduction was established based on microstructure of aerogel. Lattice Boltzmann method was used to simulate the temperature distribution and gas thermal conductivity at different size, and the size effects of gas heat conduction have had been obtained under micro-scale conditions. It can be concluded that the temperature jump on the boundary was not obvious and the thermal conductivity remained basically constant when the value of Knudsen number was less than 0.01; as the value of Knudsen number increased from 0.01 to 0.1, there was a clear temperature jump on the boundary and the thermal conductivity tended to decrease and the effect of boundary scattering increased drastically, as the value of Knudsen number was more than 0.1, the temperature jump increased significantly on the boundary, furtherly, the thermal conductivity decreased dramatically, and the size effects were significantly.

The Slip Problems for a Simple Gas

1971 ◽  
Vol 26 (6) ◽  
pp. 964-972 ◽  
Author(s):  
S.K. Loyalka
Keyword(s):  
Boltzmann Equation ◽  
Temperature Jump ◽  
Velocity Slip ◽  
Polyatomic Gas ◽  
Extra Effort ◽  
Linearized Boltzmann Equation ◽  
Multicomponent Gas ◽  
Interaction Law ◽  
Temperature Jump Coefficient ◽  
Polyatomic Gas Mixtures

Abstract Simple and accurate expressions for the velocity slip coefficient, the slip in the thermal creep, and the temperature jump coefficient are obtained by applying a variational technique to the linearized Boltzmann equation for a simple gas. Completely general forms of the boundary conditions are used, and the final results are presented in a form such that the results for any particular intermolecular force law or the gas-surface interaction law can easily be calculated. Further, it is shown that, with little extra effort, the present results can be easily extended to include the case of a polyatomic gas. It is felt that the present work, together with a recent paper in which the author has considered the solutions of the linearized Boltzmann equation for a monatomic multicomponent gas mixture, provide the desired basis for the consideration of the various slip problems associated with the polyatomic gas mixtures.

Free Convection Effects on Stokes’ Problem for a Vertical Plate in Rarefied Gas-Medium

1978 ◽  
Vol 45 (3) ◽  
pp. 697-699 ◽  
Author(s):  
V. M. Soundalgekar ◽  
S. G. Pohanerkar ◽  
M. R. Patil
Keyword(s):  
Free Convection ◽  
Vertical Plate ◽  
Temperature Jump ◽  
Rarefied Gas ◽  
Stokes Problem ◽  
Velocity Slip ◽  
First Order ◽  
Temperature Jump Coefficient ◽  
Gas Medium ◽  
Infinite Vertical Plate

An exact analysis of Stokes’ problem for the flow past an impulsively started infinite vertical plate in a rarefied gas-medium has been presented under first-order velocity slip and temperature jump boundary conditions. The effects of an externally heating or cooling of the plate by the free convection currents are studied. It is observed that there may exist a reverse type of flow when the plate is being cooled by the free convection currents. The rate of heat transfer has been found to decrease with increasing the temperature jump coefficient h2.

Fabrication of Superhydrophobic Surface by Modulating Morphology of the Organogel

Soft Matter ◽  
2021 ◽  
Author(s):  
Jianchen Zhu ◽  
Tian ren Zhang ◽  
Yajie Liu ◽  
Daoyi Lu ◽  
Peng Zhang ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Superhydrophobic Surface ◽  
Superhydrophobic Surfaces ◽  
Low Molecular Weight

A kind of low-molecular weight organic gelator (LMOG) bearing hydrazine linkage and end-capped by alkoxy-substituted phenyl, namely 1, 4-bis[(3, 4-bisoctyloxyphenyl)hydrozide]phenylene (BPH-8), was used to facilely fabricate superhydrophobic surfaces by drop-casting...

Stretchable dual cross-linked silicon elastomer with superhydrophobic surface and fast triple self-healing ability at room temperature

Soft Matter ◽  
2021 ◽  
Author(s):  
Yuxing Shan ◽  
shuai liang ◽  
Xiangkai Mao ◽  
Jie Lu ◽  
Lili Liu ◽  
...  
Keyword(s):  
Superhydrophobic Surface ◽  
Room Temperature ◽  
Superhydrophobic Surfaces ◽  
Self Healing ◽  
Wearable Electronics ◽  
Actual Application ◽  
Potential Applications

Abstract. Stretchable elastomers with superhydrophobic surfaces have potential applications in wearable electronics. However, various types of damage inevitably occur on these elastomers in actual application, resulting in deterioration of the...

scholarly journals Thermal radiation effects on the onset of unsteadiness of fluid flow in vertical microchannel filled with highly absorbing medium

2016 ◽  
Vol 20 (5) ◽  
pp. 1585-1596 ◽  
Author(s):  
Jamalabadia Abdollahzadeh ◽  
Hyun Park ◽  
Chang Lee
Keyword(s):  
Reynolds Number ◽  
Nusselt Number ◽  
Thermal Radiation ◽  
Skin Friction ◽  
Temperature Jump ◽  
Velocity Slip ◽  
Radiation Parameter ◽  
Absorbing Medium ◽  
Grashof Number ◽  
Temperature Parameter

This study presents the effect of thermal radiation on the steady flow in a vertical micro channel filled with highly absorbing medium. The governing equations (mass, momentum and energy equation with Rosseland approximation and slip boundary condition) are solved analytically. The effects of thermal radiation parameter, the temperature parameter, Reynolds number, Grashof number, velocity slip length, and temperature jump on the velocity and temperature profiles, Nusselt number, and skin friction coefficient are investigated. Results show that the skin friction and the Nusselt number are increased with increase in Grashof number, velocity slip, and pressure gradient while temperature jump and Reynolds number have an adverse effect on them. Furthermore, a criterion for the flow unsteadiness based on the temperature parameter, thermal radiation parameter, and the temperature jump is presented.

Magnetic Erasures Due to Impact Induced Interfacial Heating and Magnetostriction

1999 ◽  
Vol 122 (1) ◽  
pp. 264-268 ◽  
Author(s):  
M. Suk ◽  
P. Dennig ◽  
D. Gillis
Keyword(s):  
Thermal Conductivity ◽  
High Speed ◽  
Magnetic Layer ◽  
Substrate Material ◽  
Contact Stresses ◽  
Dominant Factor ◽  
Disk Drives ◽  
Mechanical Contact ◽  
Low Thermal Conductivity ◽  
Interfacial Temperature

High-velocity intermittent contacts between a slider and a disk may lead to data erasure due to interfacial heating and high-speed mechanical contact stresses. These potential modes of erasure are investigated by artificially introducing high contact stresses that are not likely to be observed in disk drives. Nevertheless, the mechanisms of erasure are delineated in this study with little ambiguity by comparing the results from three different substrate materials, namely Al-Mg, glass, and Si. We show that written flux patterns can be erased if either the substrate material has low thermal conductivity or if the magnetic layer is damaged. We conclude that if the disk is not plastically damaged by high-speed contacts, then the magnetostriction effect or stress-induced erasure is insignificant. In this case, the dominant factor in erasure is a rise in the interfacial temperature, which is exacerbated by low thermal conductivity of the substrate. [S0742-4787(00)03401-9]

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