Effect of Electric Field Distribution Generated in a Microspace on Pool Boiling Heat Transfer

2014 ◽  
Vol 136 (10) ◽  
Author(s):  
Ichiro Kano
Keyword(s):  
Electric Field ◽  
Traveling Wave ◽  
Electric Field Distribution ◽  
Pool Boiling ◽  
Heating Surface ◽  
Wave Model ◽  
Nucleate Boiling ◽  
Working Fluid ◽  
Helmholtz Instability ◽  
Good Agreement

This study describes the effect of an electric field on nucleate boiling and critical heat flux (CHF) in pool boiling. A dielectric liquid of AE-3000 was used as the working fluid. A heating surface was polished to a surface roughness of 0.05 μm. A microsized electrode, in which slits were provided, was designed to generate a nonuniform electric field and produce electrohydrodynamic (EHD) effects with the application of high dc voltages. The obtained results confirmed CHF enhancement as the EHD effects increased CHF to 86.2 W/cm2 with a voltage of −3000 V, which was four times greater than pool boiling in the absence of the electrode. The usual traveling wave on the bubble interface, induced by the Kelvin–Helmholtz instability, was modified by adding the EHD effects. The traveling wave model exhibits the essential features of the phenomenon and shows good agreement with the experimental data.

Effect of Electric Field Distribution Generated in a Micro Space on Pool Boiling Heat Transfer

2013 ◽  
Author(s):  
Ichiro Kano ◽  
Kyohei Sato
Keyword(s):  
Electric Field ◽  
Traveling Wave ◽  
Boiling Heat Transfer ◽  
Electric Field Distribution ◽  
Pool Boiling ◽  
Heating Surface ◽  
Nucleate Boiling ◽  
Uniform Electric Field ◽  
Working Fluid ◽  
Helmholtz Instability

This paper describes results from an experimental study of the effect of an electric field on nucleate boiling and the critical heat flux (CHF) in pool boiling. A dielectric liquid of AE-3000 (AGC Co. Ltd) was used as working fluid. A heating surface was polished with the surface roughness (Ra) of 0.05 μm. A micro sized electrode, in which the slits were provided, was designed in order to generate non uniform electric field and to produce electrohydrodynamic (EHD) effects with the application of high dc voltages. The obtained results confirmed the enhancement of CHF since the EHD effects increased the CHF to 82 W/cm2 at the voltage of −3000 V, which was four times greater than CHF for the pool boiling. The usual traveling wave on the bubble interface induced by the Kelvin-Helmholtz instability was modified by adding the EHD effects.

Analysis of the Polarity Influence on Nucleate Pool Boiling Under a DC Electric Field

1999 ◽  
Vol 121 (4) ◽  
pp. 856-864 ◽  
Author(s):  
M. C. Zaghdoudi ◽  
M. Lallemand
Keyword(s):  
Heat Transfer ◽  
Electric Field ◽  
Heat Transfer Enhancement ◽  
Field Distribution ◽  
Electric Field Distribution ◽  
Pool Boiling ◽  
Nucleate Boiling ◽  
Transfer Enhancement ◽  
Field Polarity ◽  
The One

An experimental study of the action of an intense electric field on the pool boiling of n-pentane is presented. By the application of a 25 kV/cm electric field strength, a threefold heat transfer enhancement is obtained. The effect of the electric field polarity has been researched. In nucleate boiling, the negative polarity allows to obtain a heat transfer enhancement, which is better than the one obtained in positive polarity. However, in natural convection and near the critical heat flux, the polarity of the electric field has a low influence on the heat transfer. The interpretations of the observed results are based on the action of the electric field on the boiling phenomenon and more particularly on the analysis of the electric field distribution between the electrodes. The influence of the space charge injection and the effect of the temperature on the electric field distribution have been investigated. The results obtained in the two cases of polarity are discussed in terms of effects of electrical and thermal phenomena on the distribution of the electric field between the electrodes.

Experimental Study of Boiling Phenomena by Micro/Milli Hydrophobic Dot on the Silicon Surface in Pool Boiling

2009 ◽  
Author(s):  
Hang Jin Jo ◽  
Hyungmo Kim ◽  
Ho Seon Ahn ◽  
Seontae Kim ◽  
Soon Ho Kang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Contact Angle ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Silicon Surface ◽  
Room Temperature ◽  
Pool Boiling ◽  
Heating Surface ◽  
Nucleate Boiling ◽  
Working Fluid

Many pool boiling experiments to enhance the nucleate boiling condition have been conducted and could get brilliant and challengeable results. A consensus was that CHF and heat transfer were affected by a modified heating surface. One of the efforts was the nanofluids experiments, and they have exhibited an incredible enhancement of CHF when nanofluids have been used as a working fluid in pool boiling. The results also have showed clearly that such large CHF enhancement came from the deposition of nanoparticles on the heating surface changing the surface condition. The surface covered by oxidized metal nanoparticles has a high wettability, and so it affects CHF. The fact that the wettability effect is significant to the enhancement of CHF is also supported by other kinds of boiling experiments. In addition, many researchers reported that wettability enhances not only CHF but also nucleate boiling heat transfer coefficient. In this regard, the excellent boiling performance (a high CHF and a high heat transfer coefficient) in pool boiling could be achieved through some favorable surface modification which satisfies the optimized wettability condition. For finding the optimized condition, we design the special heaters to examine how two materials, which have different wettabilities, affect the boiling phenomena. The special heaters have hydrophobic dots on the silicon surface. The hydrophobic dots lead to an early bubble inception. The bubble interface is bounded on the material boundary. The peculiar teflon(AF1600) is used as the hydrophobic material. The contact angle of the heating surface which is made by teflon is 120° to water at the room temperature. The contact angle of the silicon surface is 60° at the room temperature. The experiments using the micro hydrophobic dots and milli hydrophobic dot are performed, and the results are compared with the reference surface.

Development of Boiling Type Cooling System Using Electrohydrodynamics Effect

2013 ◽  
Vol 135 (9) ◽  
Author(s):  
Ichiro Kano ◽  
Yuta Higuchi ◽  
Tadashi Chika
Keyword(s):  
Heat Flux ◽  
Electric Field ◽  
Critical Heat Flux ◽  
Electric Fields ◽  
Cooling System ◽  
Surface Condition ◽  
Heating Surface ◽  
Nucleate Boiling ◽  
Working Fluid ◽  
High Electric Fields

This paper describes results from an experimental study of the effect of an electric field on nucleate boiling and the critical heat flux (CHF) in pool boiling at atmospheric pressure. A dielectric liquid of HFE-7100 (3 M Co.) was used as working fluid. A heating surface was polished with the surface roughness (Ra) of 0.05 μm. A microsized electrode, in which the slits were provided, was designed in order to generate non uniform high electric fields and to produce electrohydrodynamic (EHD) effects with the application of high voltages. The obtained results confirmed the enhancement of CHF since the EHD effects increased the CHF to 47 W/cm2 at the voltage of −1500 V, which was three times as much as CHF for the free convection boiling. From the observations of the behavior of bubbles over the electrode and of the boiling surface condition, the instability between the liquid and the vapor increased the heat flux, the heat transfer coefficient (HTC), and the CHF. The usual traveling wave on the bubble interface induced by the Kelvin-Helmholtz instability was modified by adding the EHD effects. The ratio of critical heat flux increase with and without the electric field was sufficiently predicted by the frequency ratio of liquid–vapor surface at the gap between the boiling surface and the electrode.

Experimental Verification of Analytical Prediction of Pool Boiling CHF Incorporating the Effects of EHD and Contact Angle

2015 ◽  
Author(s):  
Ichiro Kano ◽  
Takahiro Sato ◽  
Naoki Okamoto
Keyword(s):  
Heat Transfer ◽  
Contact Angle ◽  
Electric Field ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Contact Angles ◽  
Dielectric Liquid ◽  
Working Fluid ◽  
Analytical Prediction ◽  
Compound Effect

Boiling heat transfer enhancement via compound effect of Electro-Hydro-Dynamic (EHD) and contact angle has been experimentally and analytically investigated. A fluorinated dielectric liquid (Asahi Glass Co. Ltd, AE-3000) was selected as the working fluid. Pool boiling heat transfer in the saturated liquid was measured at atmospheric pressure. In order to change the contact angle between the boiling surface and the dielectric liquid, the different materials Cu, Cr, NiB, Sn, and mixture of 5 and 1.5 micro meter diamond particles were electrically deposited on a boiling surface. The critical heat flux (CHF) for different contact angles showed 20.5 ∼ 26.9 W/cm2 which was −7 ∼ 25 % of that for a non-coated Cu surface (21.5 W/cm2). Upon application of a −5 kV/mm electric field to the micro structured surface (the mixture of 5 and 1.5 micro meter particles), a CHF of 99 W/cm2 at a superheat of 33.5 K was obtained. The previous theoretical equation of pool boiling predicted the CHF with the electric field and without the electrode.

ELECTRIC FIELD INFLUENCE ON TRAVELING WAVE PROPAGATION AND STATIONARY PATTERN FORMATION

1995 ◽  
Vol 05 (03) ◽  
pp. 797-807 ◽  
Author(s):  
J. MOSQUERA ◽  
M. GÓMEZ-GESTEIRA ◽  
V. PÉREZ-MUÑUZURI ◽  
A.P. MUÑUZURI ◽  
V. PÉREZ-VILLAR
Keyword(s):  
Wave Propagation ◽  
Pattern Formation ◽  
Electric Field ◽  
Electric Fields ◽  
Traveling Wave ◽  
Traveling Fronts ◽  
Spatial Terms ◽  
Oregonator Model ◽  
Field Influence ◽  
Good Agreement

The electric field influence on pattern formation and traveling wave propagation is investigated in the framework of the Oregonator model. When an electric field is applied to a system that can suffer spatial instabilities, Turing and Turing-like patterns (traveling fronts that become stationary patterns when reaching a zero-flux boundary) are observed. On the other hand, when an electric field is applied to a system that cannot become unstable by spatial terms and where wavefronts are propagating in the absence of electric fields, the velocity of these wavefronts is modified and can even be reversed. This is in good agreement with previous experimental results.

Experimental and Numerical Study of the Effects of Asymmetric Micro Ratchets on Pool Boiling Performance

2013 ◽  
Author(s):  
Lance Brumfield ◽  
Sunggook Park
Keyword(s):  
High Performance ◽  
Numerical Study ◽  
Heated Surface ◽  
Pool Boiling ◽  
Nucleate Boiling ◽  
Industrial Applications ◽  
Heat Fluxes ◽  
Working Fluid ◽  
High Heat Flux ◽  
Central Processing

Nucleate boiling is an attractive method for achieving high heat flux at low superheat temperatures. It is frequently used for industrial applications such as heat exchangers and is being considered to cool advanced central processing units (CPU) which produce heat fluxes on the order of 1 MW/m2 and are becoming increasingly less efficient to cool via forced conduction of air. The issues with implementing nucleate boiling as a cooling mechanism lies in the difficulty of quantifying the complex and numerous mechanisms which control the process. A comprehensive nucleate boiling model has yet to be formulated and will be required in order to safely and reliably cool high performance electronics. Spatially periodic systems with localized asymmetric surface structures (ratchets) can induce directed transport of matter (liquid/particles) in the absence of net force. It was hypothesized that ratchets may enhance pool boiling heat transfer by aiding in the removal of vapor which forms on the heated surface. Therefore, experiments on pool boiling using asymmetric micro ratchets of various geometries, with FC-72 as the working fluid, were investigated. Additionally, various numerical pool boiling simulations were performed using FLUENT to better understand the underlying physical principles behind pool boiling.

On the compact modelling of Si nanowire and Si nanosheet MOSFETs

2021 ◽  
Author(s):  
Antonio Cerdeira ◽  
Magali Estrada ◽  
Marcelo Antonio Pavanello
Keyword(s):  
Electric Field ◽  
Electron Concentration ◽  
Current Density ◽  
Electric Field Distribution ◽  
Double Gate ◽  
Si Nanowire ◽  
Circuit Simulator ◽  
Aspect Ratios ◽  
Good Agreement ◽  
Tcad Simulations

Abstract In this paper, 3D TCAD simulations are used to show that the electron concentration, current density, and electric field distribution from the interface at the lateral channels and from the top channel to the centre of the silicon wire, in Nanowire and Nanosheet structures, are practically same. This characteristic makes possible to consider that the total channel width for these structures is equal to the perimeter of the transistor sheet, allowing to extend the application of the Symmetric Doped Double-Gate Model (SDDGM) model to Nanowires and Nanosheets MOSFETs, with no need to include new parameters. The Model SDDGM is validated for this application using several measured and simulated structures of Nanowires and Nanosheets transistors, with different aspect ratios of fin width and fin height, showing very good agreement between measured or simulated characteristics and modelled. SDDGM is encoded in Verilog-A language and implemented in SmartSPICE circuit simulator.

Nucleate Boiling on Biotemplated Nanostructured Surfaces

2012 ◽  
Author(s):  
Md. Mahamudur Rahman ◽  
Stephen M. King ◽  
Emre Olceroglu ◽  
Matthew McCarthy
Keyword(s):  
Heat Transfer ◽  
Self Assembly ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Nucleate Boiling ◽  
Pool Boiling Heat Transfer ◽  
Nanostructured Surfaces ◽  
Transfer Capability ◽  
Good Agreement

The fabrication and characterization of biotemplated nanostructured surfaces for enhanced pool boiling heat transfer is reported. By introducing micro/nano-porosity and surface roughness at the liquid-vapor interface, significant enhancement in surface heat transfer capability can be achieved during nucleate boiling. This work uses the self-assembly and mineralization of the Tobacco mosaic virus (TMV) to create superhydrophilic (∼9°), superhydrophobic (∼163°), and mixed hydrophilic-hydrophobic (∼70°) surfaces to investigate the effects of surface wettability and heterogeneity on boiling heat transfer performance. Pool boiling results showing CHF and HTC values for nickel-coated TMV, Teflon-coated TMV, mixed nickel + Teflon coated TMV, flat silicon, and flat Teflon are reported. The mixed surfaces demonstrate a CHF enhancement of ∼ 70% compared to flat silicon and ∼140% compared to flat Teflon. The results are in good agreement with the literature and will guide the design of optimized surfaces for further enhancement. This work demonstrates the feasibility of enhancing pool boiling heat transfer using TMV based nanostructured coatings.

The Whole Simulation Analysis and Measurement of the Power Frequency Electric Field in 500kV Substation

2014 ◽  
Vol 672-674 ◽  
pp. 837-841
Author(s):  
Luo Peng ◽  
Li Yong Ming
Keyword(s):  
Electric Field ◽  
Electric Field Distribution ◽  
Simulation Analysis ◽  
Simulation Method ◽  
Rapid Analysis ◽  
Charge Simulation Method ◽  
Power Frequency ◽  
Frequency Electric Field ◽  
Distribution Of Power ◽  
Good Agreement

An improved Charge Simulation Method (CSM) is proposed in this paper. Based on this method, the model of the overall 500kV substation is established, and then the power frequency electric field in substation at the height of the 1.5mabovethegroundis simulated and calculated. Specifically, these on 500kV switch yard in the station are simulated and analysis. The results show that the simulation results are in good agreement with the actual substation measured results, which is proved the correctness of the model and the algorithm. This paper provides an effective method for the rapid analysis of the distribution of power frequency electric field in ultra-high-voltage substation, and also can use the method to study the effects of electric field distribution factors in substation.

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