scholarly journals Combined Dielectrophoretic and Electrohydrodynamic Conduction Pumping for Enhancement of Liquid Film Flow Boiling

2017 ◽  
Vol 139 (6) ◽  
Author(s):  
Viral K. Patel ◽  
Jamal Seyed-Yagoobi
Keyword(s):  
Heat Transfer ◽  
Liquid Film ◽  
Film Flow ◽  
Flow Boiling ◽  
Nucleate Boiling ◽  
Transport Systems ◽  
Heater Surface ◽  
Force Magnitude ◽  
Boiling Heat Transfer Coefficient ◽  
Liquid Film Flow

This paper extends previous liquid film flow boiling studies by including the effect of an additional electrohydrodynamic (EHD) force, namely, the dielectrophoretic (DEP) force. Rather than using only EHD conduction pumping of the liquid film to electro-wet the heater surface, a localized nonuniform electric field above the heater surface is established to generate a DEP force for improved vapor bubble extraction during the nucleate boiling regime. The effects of liquid film height and applied potential are studied as a function of heater superheat and heat flux. A brief analytical study is also used to estimate the expected DEP force magnitude to explain the results. All of the above studies are also used to quantify the enhancement in heat transfer that can be achieved when heat transport systems are driven or augmented by these two EHD mechanisms. The results show remarkable enhancement of up to 1217% in boiling heat transfer coefficient at a given superheat when both mechanisms are used simultaneously. The experimental data are important for applications in thermal management in terrestrial and space conditions.

Combined Electrohydrodynamic Conduction Pumping and Dielectrophoresis for Enhancement of Liquid Film Flow Boiling

2015 ◽  
Author(s):  
Viral K. Patel ◽  
Jamal Seyed-Yagoobi
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Liquid Film ◽  
Film Flow ◽  
Flow Boiling ◽  
Nucleate Boiling ◽  
Transport Systems ◽  
Heater Surface ◽  
Dielectrophoretic Force ◽  
Liquid Film Flow

The research in this paper extends previous liquid film flow boiling studies by including the effect of an additional electrohydrodynamic (EHD) force, namely the dielectrophoretic (DEP) force. Rather than using only EHD conduction pumping of the liquid film to electro-wet the heater surface, a localized non-uniform electric field above the heater surface is also used to generate a dielectrophoretic force for improved vapor bubble extraction during the nucleate boiling regime. The effect of liquid film height and applied potential are studied as a function of heater superheat and heat flux. The study considers the sole and combined effect of DEP with EHD conduction pumping. A brief analytical study is also used to estimate the expected dielectrophoretic force magnitude and explain the results. All of the above studies are also used to quantify the enhancement in heat transfer that can be achieved when heat transport systems are driven or augmented by these electrohydrodynamic phenomena. The results show remarkable enhancement of up to 1217% in heat flux and boiling heat transfer coefficient for a given superheat when both mechanisms are used simultaneously. The experimental data are important for applications in thermal management in terrestrial and micro-gravity conditions.

Electrohydrodynamic Conduction Pumping-Driven Liquid Film Flow Boiling on Bare and Nanofiber-Enhanced Surfaces

2015 ◽  
Vol 138 (4) ◽  
Author(s):  
Viral K. Patel ◽  
Jamal Seyed-Yagoobi ◽  
Suman Sinha-Ray ◽  
Sumit Sinha-Ray ◽  
Alexander Yarin
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Liquid Film ◽  
Boiling Heat Transfer ◽  
Film Flow ◽  
Flow Boiling ◽  
Copper Substrate ◽  
Polymer Nanofiber ◽  
Liquid Film Flow ◽  
Bare Surface

Liquid film flow boiling heat transfer driven by electrohydrodynamic (EHD) conduction pumping is experimentally studied on a surface with a novel metal-plated nanofiber-mat coating. The nanotextured surface is formed on a copper substrate covered by an electrospun polymer nanofiber mat, which is copper-plated as a postprocess. The mat has a thickness of about 30 μm and is immersed in saturated HCFC-123. The objective is to study electrowetting of the copper-plated nanofiber-enhanced surface via EHD conduction pumping mechanism for the entire liquid film flow boiling regime leading up to critical heat flux (CHF), and compare it to the bare surface without EHD-driven flow. The results show that with the combination of these two techniques, for a given superheat value, enhancement in heat flux and boiling heat transfer coefficient is as high as 555% compared to the bare surface. The results are quite promising for thermal management applications.

Theoretical and Experimental Analysis of Turbulent Liquid Film Flowing down a Vertical Surface

2009 ◽  
Vol 15 ◽  
pp. 3-8
Author(s):  
Stasys Sinkunas ◽  
Jonas Gylys ◽  
Algimantas Kiela
Keyword(s):  
Heat Transfer ◽  
Liquid Film ◽  
Analytical Study ◽  
Film Flow ◽  
Convex Surface ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Vertical Surface ◽  
Momentum And Heat Transfer ◽  
Liquid Film Flow

The purpose of the present study is to obtain a comprehension for the momentum and heat transfer developments in gravitational liquid film flow. Analytical study of stabilized heat transfer for turbulent film was performed. A calculation method of the local heat transfer coefficient for a turbulent film falling down a vertical convex surface was proposed. The dependence of heat flux variation upon the distance from the wetted surface has been established analytically. Experimental study of velocity profiles for turbulent liquid film flow in the entrance region is performed as well. Analysis of profiles allowed estimating the length of stabilization for turbulent film flow under different initial velocities.

Effect of Gravity on Electrohydrodynamic Conduction Driven Liquid Film Flow Boiling

2016 ◽  
Vol 30 (2) ◽  
pp. 429-437 ◽  
Author(s):  
Viral K. Patel ◽  
Jamal Seyed-Yagoobi ◽  
Franklin Robinson ◽  
Jeffrey R. Didion
Keyword(s):  
Liquid Film ◽  
Film Flow ◽  
Flow Boiling ◽  
Liquid Film Flow

Experimental Study of Flow Boiling Heat Transfer Coefficient of FC-72 Over Micro-Pin-Finned Surfaces

2010 ◽  
Author(s):  
Y. F. Xue ◽  
M. Z. Yuan ◽  
J. J. Wei
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Fluid Velocity ◽  
Nucleate Boiling ◽  
Flow Boiling Heat Transfer ◽  
Nucleate Boiling Heat Transfer ◽  
Boiling Heat Transfer Coefficient

Experiments of flow boiling heat transfer coefficient of FC-72 were carried out over simulated silicon chip of 10×10×0.5 mm3 for electronic cooling. Four kinds of micro-pin-fins with the dimensions of 30×60, 30×120, 50×60, 50×120 μm2 (thickness, t × height, h) respectively, were fabricated on the chip surfaces by the dry etching technique to enhance boiling heat transfer. A smooth chip was also tested for comparison. The experiments were conducted at three different fluid velocities (0.5, 1 and 2m/s) and three different liquid subcoolings (15, 25 and 35K). All micro-pin-finned surfaces show a considerable heat transfer enhancement compared to the smooth surface. Both the forced convection and nucleate boiling heat transfer contribute to the total heat transfer performance. The contribution of each factor to the total heat transfer has been clearly presented in the flow boiling heat transfer coefficient curves. In a lower heat flux region, the heat transfer coefficient increases greatly with increasing fluid velocity, but increases slightly with increasing heat flux, indicating that the single-phase forced convection dominates the heat transfer process. With further increasing heat flux to the onset of nucleate boiling, the heat transfer coefficient increases remarkably. For a given liquid subcooling, the curves of flow boiling heat transfer coefficient at fluid velocities of 0.5 and 1 m/s almost follow one line for each surface, showing insensitivity of nucleate boiling heat transfer to fluid velocity. However, at the largest fluid velocity of 2 m/s, the slope of the flow boiling heat transfer coefficient curves for micro-pin-finned surfaces becomes smaller, indicating that the forced convection also plays an important role besides the nucleate boiling heat transfer. The curves of the flow boiling heat transfer coefficient can be used to determine the boiling incipience at different fluid velocities, which provides a basis for the suitable fluid velocity selection in designing highly efficient cooling scheme for electronic devices.

Annular Liquid Film Flow Under Local Heating in Microchannel

2005 ◽  
Author(s):  
Elizaveta Ya. Gatapova ◽  
Vladimir V. Kuznetsov ◽  
Oleg A. Kabov ◽  
Jean-Claude Legros
Keyword(s):  
Heat Transfer ◽  
Liquid Film ◽  
Biot Number ◽  
Gas Flow ◽  
Film Flow ◽  
Local Heating ◽  
Local Heat Transfer ◽  
Flow Region ◽  
Local Heat ◽  
Liquid Film Flow

In our previous investigations the formation of liquid bump of locally heated laminar liquid film with co-current gas flow was obtained [1,2]. The evaporation of liquid was left out of account. Heat transfer to the gas phase was approximately specified by a constant Biot number [2,3]. The aim of this work is an investigation of the evaporation effect, the hydrodynamics and the heat transfer of liquid film flow in a channel 0.2–1 mm height. The 2-D model of locally heated liquid film moving under gravity and the action of co-current gas flow with low viscosity in a channel are considered. The channel can be inclined at an angle with respect to horizon. It is supposed that the height of the channel is much less than its width. Surface tension is assumed to depend on temperature. The velocity profiles for gas and liquid regions are found from problem of joint motion of isothermal non-deformable liquid film and gas flow. Using the findings the joint solution of heat transfer and diffusion problem with corresponding boundary condition is calculated. Having the temperature field in the whole of liquid and gas flow region we find a local heat transfer coefficient on the gas-liquid interface and Biot number as a function of flow parameters and spatial variables.

Low-Velocity Subcooled Nucleate Flow Boiling at Various Orientations

1995 ◽  
Vol 117 (2) ◽  
pp. 380-386 ◽  
Author(s):  
K. M. Kirk ◽  
H. Merte ◽  
R. Keller
Keyword(s):  
Thin Film ◽  
Heat Transfer ◽  
Liquid Velocity ◽  
Flow Boiling ◽  
Copper Substrate ◽  
Nucleate Boiling ◽  
Bulk Liquid ◽  
Heater Surface ◽  
Low Velocity ◽  
Buoyant Force

Subcooled forced convection nucleate boiling experiments with R-113 were conducted at low velocities using both thin film semitransparent gold-on-quartz and gold-coated copper substrate flat heaters at various orientations. The experiments demonstrate that if buoyancy is significant relative to bulk liquid momentum, then a decrease in the buoyant force normal to and away from the heater surface enhances the heat transfer, with the effect being greatest at low values of heat flux. Furthermore, the effect of the bulk liquid velocity is shown to be dependent on the surface orientation.

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