Theoretical Model of Droplets Motions on Solid Surface With Radial Wettable and Evaporation Rate Gradients

2018 ◽  
Author(s):  
Yanjie Yang ◽  
Zan Wu ◽  
Xiaoqian Chen ◽  
Bengt Sundén ◽  
Yiyong Huang
Keyword(s):  
Surface Tension ◽  
Theoretical Model ◽  
Solid Surface ◽  
Radial Direction ◽  
Evaporation Rate ◽  
Marangoni Effect ◽  
Droplet Radius ◽  
Surface Tension Gradient ◽  
Capillary Length ◽  
Liquid Vapor

Wettability gradient in radial direction and evaporation rate gradient can cause droplet motion on a solid surface. Here a theoretical model is proposed. Besides, an equation of droplet velocity is derived on a solid surface. We consider the wettability and evaporation rate gradients are mainly caused by the chemical composition and surface roughness, only along the radial direction. Surface tension at the liquid-vapor interface is constant as it is assumed that the temperature does not change during the whole process. Thus, Marangoni effect induced by the liquid-vapor surface tension gradient is neglected. Besides, as droplet size is set as less than the capillary length (l=γ/ρg), the gravity effect is ignored as well. The velocity at the droplet center on a gradient surface along the radial direction is half of that along the x-direction. With the simulation of water droplet, the center velocity decreases with time and the droplet radius increases at the beginning part and then decreases.

Suppression of Thermocapillary Effect in Evaporating Thin Film of Micro Heat Pipes

2015 ◽  
Vol 1101 ◽  
pp. 467-470
Author(s):  
Elaine Lim ◽  
Yew Mun Hung
Keyword(s):  
Surface Tension ◽  
Thin Liquid Film ◽  
Marangoni Effect ◽  
Working Fluid ◽  
Surface Tension Gradient ◽  
Flow Mechanism ◽  
Thermocapillary Effect ◽  
Micro Heat Pipes ◽  
Thermo Physical Properties ◽  
Microelectronics Cooling

This paper presents a theoretical study on the flow mechanism of different types of working fluids incorporated with Marangoni effect in a microelectronics cooling device. It is known that surface tension gradient effect or thermocapillary effect can be induced by temperature gradient which leads to the thermocapillary flow. By adding a small quantity of alcohol into the pure working fluid, the characteristics of surface tension can be altered without changing other thermo physical properties of the working fluid. A theoretical model is employed to focus on the suppression of thermocapillary effect in evaporating thin liquid film. The study reveals the fluid flow mechanism of a working fluid can be altered with thermocapillary effect. Thermal performance of microelectronics cooling devices can also be enhanced by utilizing aqueous solution as the working fluid.

scholarly journals Study on the Instability of Two-Phase Flow in the Heat-Absorbing Tube of Trough Solar Collector

2017 ◽  
Vol 2017 ◽  
pp. 1-8
Author(s):  
Ying Zhang ◽  
Peiyao Liu ◽  
Peisheng Li ◽  
Yue Chen ◽  
Yanni Pan
Keyword(s):  
Surface Tension ◽  
Temperature Gradient ◽  
Velocity Gradient ◽  
Marangoni Effect ◽  
Surface Tension Gradient ◽  
Promoting Effect ◽  
Two Phase ◽  
Buoyancy Convection ◽  
Interface Wave ◽  
Rayleigh Benard

The Marangoni effect and Rayleigh-Benard effect in the two-phase region of solar trough heat-absorbing tube are simulated by FTM (front tracking method). Considering the Marangoni effect alone, although surface tension gradient and surface tension affect the interface wave, the two effects have different characteristics. The surface tension gradient caused by the temperature gradient is one of the factors that swing the interface. The amplitude attenuation of the interface wave decreases with the increase of the Marangoni number (Ma). In general, the surface tension gradient enhances the convection opposite to the temperature gradient. Under the gravity field, the Rayleigh-Benard effect influences the development of the vortex structure in the flow field, which in turn affects the velocity gradient near the interface to influence the evolution of the interface fluctuation. In a small Rayleigh number (Ra), the buoyancy convection reduces the velocity gradient, thus suppressing the evolution of the interfacial wave. In the range of Ra < 4.0E4, the larger the Ra, the stronger the inhibitory effect. However, when the Ra number is large (Ra > 4.0E4), the situation is just the opposite. The larger the Ra is, the stronger the promoting effect is.

A new hydrodynamic interpretation of liquid metal droplet motion induced by electrocapillary phenomenon

Soft Matter ◽  
2021 ◽  
Author(s):  
Jiao Ye ◽  
Si-Cong Tan ◽  
Lei Wang ◽  
Jing Liu
Keyword(s):  
Surface Tension ◽  
Liquid Metal ◽  
Electric Potential ◽  
Potential Gradient ◽  
Marangoni Effect ◽  
Metal Droplet ◽  
Surface Tension Gradient ◽  
Droplet Motion ◽  
Liquid Metal Droplet

The Marangoni effect, induced by the surface tension gradient resulting from the gradient of temperature, concentration, or electric potential gradient along the surface, is commonly utilized to manipulate a droplet....

On the Role of Marangoni Effects on the Critical Heat Flux for Pool Boiling of Binary Mixtures

1996 ◽  
Vol 118 (1) ◽  
pp. 103-109 ◽  
Author(s):  
W. R. McGillis ◽  
V. P. Carey
Keyword(s):  
Surface Tension ◽  
Heat Flux ◽  
Binary Mixtures ◽  
Critical Heat Flux ◽  
Full Range ◽  
Pool Boiling ◽  
Marangoni Effect ◽  
Restoring Force ◽  
Marangoni Effects

The Marangoni effect on the critical heat flux (CHF) condition in pool boiling of binary mixtures has been identified and its effect has been quantitatively estimated with a modified model derived from hydrodynamics. The physical process of CHF in binary mixtures, and models used to describe it, are examined in the light of recent experimental evidence, accurate mixture properties, and phase equilibrium revealing a correlation to surface tension gradients and volatility. A correlation is developed from a heuristic model including the additional liquid restoring force caused by surface tension gradients. The CHF condition was determined experimentally for saturated methanol/water, 2-propanol/water, and ethylene glycol/water mixtures, over the full range of concentrations, and compared to the model. The evidence in this study demonstrates that in a mixture with large differences in surface tension, there is an additional hydrodynamic restoring force affecting the CHF condition.

Breakdown of Evaporating Falling Films as a Function of Surface Tension Gradient

1996 ◽  
Vol 17 (4) ◽  
pp. 72-81 ◽  
Author(s):  
ALI G. BUDIMAN ◽  
C. FLORIJANTO ◽  
J. W. PALEN
Keyword(s):  
Surface Tension ◽  
Surface Tension Gradient ◽  
Falling Films

scholarly journals Effect of a surface tension gradient on the slip flow along a superhydrophobic air-water interface

2018 ◽  
Vol 3 (3) ◽  
Author(s):  
Dong Song ◽  
Baowei Song ◽  
Haibao Hu ◽  
Xiaosong Du ◽  
Peng Du ◽  
...  
Keyword(s):  
Surface Tension ◽  
Slip Flow ◽  
Surface Tension Gradient ◽  
Water Interface ◽  
Air Water Interface

Measurement of Burst Pressure of Capillary Burst Valve

2010 ◽  
Author(s):  
Hong Chen ◽  
Toru Yamada ◽  
Mohammad Faghri
Keyword(s):  
Surface Tension ◽  
Solid Surface ◽  
Burst Pressure ◽  
Surface Tensions ◽  
Fluid Surface ◽  
Mechanical Components

Capillary burst valve (CBV), a counterpart to an elastomeric diaphragm microvalve, handles fluid in microchannels by capillarity. Thus, it avoids integration of mechanical components. We experimentally estimated the burst pressure, beyond which CBV cannot hold fluid, using fluids with distinct surface tensions in CBVs grafted with distinct surface constitutions in microchannels. We found that both the fluid surface tension and the solid surface constitution influence the burst pressure. The burst pressure reduces more significantly under the influence of the fluid surface tension.

Ferrohydrodynamic Capillary Convection

2018 ◽  
Vol 11 (2) ◽  
Author(s):  
Francisco J. Arias ◽  
Salvador A. De Las Heras
Keyword(s):  
Magnetic Field ◽  
Surface Tension ◽  
Concentration Gradient ◽  
Deductive Reasoning ◽  
Marangoni Convection ◽  
Marangoni Effect ◽  
Magnetic Fluids ◽  
Homogeneous Magnetic Field ◽  
Gradient Field ◽  
Two Fluids

Abstract In this work, consideration is given to capillary convection on ferrofluids from the concentration gradient induced when a nonhomogeneous magnetic field is applied. It is known that mass transfer along an interface between two fluids can appear due to a gradient of the surface tension in the so-called Marangoni effect (or Gibbs–Marangoni effect). Because the surface tension is both thermal and concentration dependent, Marangoni convection can be induced by either a thermal or a concentration gradient, where in the former case, it is generally referred as thermocapillary convection. Now, it has been theoretically and experimentally demonstrated that a ferrofluid under the action of a non-homogeneous magnetic field can induce a concentration gradient of suspended magnetic nanoparticles, and also the effect of Fe3O4 nanoparticles on the surface tension has been measured. Therefore, by deductive reasoning and taking into account the above mentioned facts, it is permissible to infer ferrohydrodynamic capillary convection on magnetic fluids under the presence of a magnetic gradient field. Utilizing a simplified physical model, the phenomenon was investigated and it was found that ferrohydrodynamic-Marangoni convection could be induced with particle size in the range up to 10 nm, which is the range of magnetic fluids to escape magnetic agglomeration.

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