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.

Development of Boiling Type Cooling System Using Electrostatic and Electroconvection Force

2012 ◽  
Author(s):  
Ichiro Kano ◽  
Yuta Higuchi ◽  
Tadashi Chika
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Electric Field ◽  
Transfer Coefficient ◽  
Cooling System ◽  
Surface Condition ◽  
Nucleate Boiling ◽  
High Electric Field ◽  
The Heat Transfer Coefficient

The 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 with polished smooth boiling surface. A micro scaled electrode with slits for bubbles to come out was designed in order to create non uniform high electric field strength and to produce electrohydrodynamics (EHD) convection with the application of dc voltage. The application of high electric field strongly enhanced the heat flux and the heat transfer coefficient. From observations of the behavior of bubbles over the electrode and the boiling surface condition, the instability between the liquid and the vapor increased the heat flux, the heat transfer coefficient and the CHF.

scholarly journals ELETRIC FIELD ENHANCEMENT AND DETERIORATION OF BOILING HEAT TRANSFER AND CRITICAL HEAT FLUX IN DIELECTRIC FLUIDS

2001 ◽  
Vol 1 (1) ◽  
pp. 32
Author(s):  
P. M. Carrica ◽  
V. Masson
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Electric Fields ◽  
Boiling Heat Transfer ◽  
Nucleate Boiling ◽  
Film Boiling ◽  
Two Phase ◽  
Boiling Regime ◽  
Dielectric Fluids

We present the results of an experimental study of the effects of externally imposed electric fields on boiling heat transfer and critical heat flux (CHF) in dielectric fluids. The study comprises the analysis of geometries that, under the effects of electric fields, cause the bubbles either to be pushed toward the heater or away from it. A local phase detection probe was used to measure the void fraction and the interfacial impact rate near the heater. It was found that the critical heat flux can be either augmented or reduced with the application of an electric field, depending on the direction of . In addition, the heat transfer can be slightly enhanced or degraded depending on the heat flux. The study of the two-phase flow in nucleate boiling, only for the case of favorable dielectrophoretic forces, reveals that the application of an electric field reduces the bubble detection time and increases the detachment frequency. It also shows that the two-phase flow characteristics of the second film boiling regime resemble more a nucleate boiling regime than a film boiling regime.

Experimental Study on the Critical Heat Flux of Nanofluid Flow Boiling Under Different Conditions

2018 ◽  
Author(s):  
Y. Wang ◽  
K. H. Deng ◽  
J. M. Wu ◽  
N. N. Yue ◽  
Y. F. Zan ◽  
...  
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Mass Flux ◽  
Flow Boiling ◽  
Heating Surface ◽  
Vertical Tube ◽  
Working Fluid ◽  
Nanofluid Flow ◽  
Sem Images ◽  
Heat Transfer System

Nanofluid has been attracted great attention since it was proposed as a preeminent working fluid. Flow boiling is familiar in heat transfer system and the critical heat flux is a key parameter for the design of thermal hydraulic. In present work, the critical heat flux of nanofluid flow boiling is experimentally investigated in a vertical tube with the consideration of outlet pressure, mass flux, inlet subcooling, heating length and diameter. The results indicate that the critical heat flux of nanofluid flow boiling is enhanced compared with base fluid and the increasing radio is increased with increasing the mass flux, diameter and pressure, and with decreasing the heating length. In addition, the inlet subcooling and concentrations (0.1vol.%, 0.5vol.%) have almost no significant influence. Furthermore, a new mechanism for the enhancement of nanofluid flow boiling critical heat flux was proposed by the SEM images of nanopariticle deposition on the heating surface.

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.

scholarly journals ELETRIC FIELD ENHANCEMENT AND DETERIORATION OF BOILING HEAT TRANSFER AND CRITICAL HEAT FLUX IN DIELECTRIC FLUIDS

2002 ◽  
Vol 1 (1) ◽  
Author(s):  
P. M. Carrica ◽  
V. Masson
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Electric Fields ◽  
Boiling Heat Transfer ◽  
Nucleate Boiling ◽  
Film Boiling ◽  
Two Phase ◽  
Boiling Regime ◽  
Dielectric Fluids

We present the results of an experimental study of the effects of externally imposed electric fields on boiling heat transfer and critical heat flux (CHF) in dielectric fluids. The study comprises the analysis of geometries that, under the effects of electric fields, cause the bubbles either to be pushed toward the heater or away from it. A local phase detection probe was used to measure the void fraction and the interfacial impact rate near the heater. It was found that the critical heat flux can be either augmented or reduced with the application of an electric field, depending on the direction of . In addition, the heat transfer can be slightly enhanced or degraded depending on the heat flux. The study of the two-phase flow in nucleate boiling, only for the case of favorable dielectrophoretic forces, reveals that the application of an electric field reduces the bubble detection time and increases the detachment frequency. It also shows that the two-phase flow characteristics of the second film boiling regime resemble more a nucleate boiling regime than a film boiling regime.

scholarly journals Critical heat flux enhancement in microgravity conditions coupling microstructured surfaces and electrostatic field

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Alekos Ioannis Garivalis ◽  
Giacomo Manfredini ◽  
Giacomo Saccone ◽  
Paolo Di Marco ◽  
Artyom Kossolapov ◽  
...  
Keyword(s):  
Heat Flux ◽  
Electric Field ◽  
Critical Heat Flux ◽  
Electric Fields ◽  
Parabolic Flight ◽  
Dielectric Fluid ◽  
Two Phase ◽  
Microstructured Surfaces ◽  
Microgravity Conditions ◽  
Plain Surface

AbstractWe run pool boiling experiments with a dielectric fluid (FC-72) on Earth and on board an ESA parabolic flight aircraft able to cancel the effects of gravity, testing both highly wetting microstructured surfaces and plain surfaces and applying an external electric field that creates gravity-mimicking body forces. Our results reveal that microstructured surfaces, known to enhance the critical heat flux on Earth, are also useful in microgravity. An enhancement of the microgravity critical heat flux on a plain surface can also be obtained using the electric field. However, the best boiling performance is achieved when these techniques are used together. The effects created by microstructured surfaces and electric fields are synergistic. They enhance the critical heat flux in microgravity conditions up to 257 kW/m2, which is even higher than the value measured on Earth on a plain surface (i.e., 168 kW/m2). These results demonstrate the potential of this synergistic approach toward very compact and efficient two-phase heat transfer systems for microgravity applications.

Study on Saturated Flow Boiling Heat Transfer Under Vibration Conditions

2012 ◽  
Author(s):  
Yoshitaro Fujiyama ◽  
Hiroyasu Ohtake
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Test Section ◽  
Low Voltage ◽  
Flow Boiling ◽  
Heating Surface ◽  
Nucleate Boiling ◽  
Circuit Board ◽  
Vertical Position ◽  
Saturated Flow

The ability to predict void formation, void fraction and critical heat flux —CHF— in flow boiling under oscillatory flow and vibration conditions is important to the safety technology of nuclear reactor during earthquake. In the present study, the onset of nucleate boiling —ONB— and CHF on saturated flow boiling under vibration conditions were investigated experimentally. Steady state experiments were conducted using a copper thin-film and saturated and subcooled water at 0.1 MPa. The liquid velocity was 0.25, 1.38, 3.20 and 4.07 m/s, respectively; the liquid subcooling was 0 K and 20 K. A heater was made of a printed circuit board. A test section was a rectangular flow channel of 10 mm width and 10 mm height. The test heater was heated by Joule heating of d.c. current from a low-voltage high-current stabilizer. The heating rate of the heater was determined from supplied current and voltage. The temperature of the heater was obtained by referring to the measured electric resistance. The test section was arranged for horizontal position facing upward and for vertical position, respectively. For the vibration condition, the test section was set on a vibration table. The ONB was decided as an occurrence of the first boiling bubble. The critical heat flux was determined as that immediately before the heating surface physically burned-out. The CHF on saturated flow boiling under vibration conditions were investigated experimentally.

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.

scholarly journals Heat transfer performance and influences of spray cooling under quenching

2020 ◽  
pp. 349-349
Author(s):  
Nianyong Zhou ◽  
Hao Feng ◽  
Muhao Xu ◽  
Enhai Liu
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Cooling System ◽  
Temperature Drop ◽  
Spray Cooling ◽  
Cooling Curve ◽  
Chamber Pressure ◽  
Working Fluid ◽  
Vapor Film

In this study, a closed-loop spray cooling system using R134a as the working fluid was established. The heat transfer characteristics and influencing mechanism of transient spray cooling were studied. The transient spray cooling curve under quenching was built accurately. The results show that the vapor film suppressed time tsup is the main period that the spray cooling must pass through. The flow rate and the sub-cooling of R134a have little effect on the cooling rate but the critical heat flux, which are mainly affected by chamber pressure. The transient Jacob number Ja+ decreases with the increases of chamber pressure. As Ja+ decreases, the growth of vapor film is inhibited, then the tsup reduces in consequence. The surface temperature drop point and critical heat flux increases with the rise of chamber pressure. The maximum critical heat flux is 70.08 W/cm2in this experiment.

Pool Boiling Heat Transfer From Artificial Micro-Cavities Surface in Dielectric Liquid FC-72

2004 ◽  
Author(s):  
C. K. Yu ◽  
D. C. Lu ◽  
T. C. Cheng ◽  
B. C. Tsai
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Nucleate Boiling ◽  
Working Fluid ◽  
Pronounced Increase ◽  
Pool Boiling Heat Transfer ◽  
Micro Cavity

Pool boiling heat transfer phenomenon of artificial micro-cavity enhanced surfaces by wet etching MEMS fabrication immersed in a saturated dielectric fluid has been experimentally studied. The present research is to investigate pool boiling behavior including heat transfer performance and flow pattern of “artificial micro cavities” heating surfaces simulating microelectronic devices at atmospheric pressure with FC-72 as the working fluid. The test surfaces are the solid silicon based blocks with 200 μm diameter circular cavities with flat plane, 16 × 16, 25 × 25, 33 × 33 array and 50 μm depth. Effects of this double enhancement technique on critical heat flux (CHF) and nucleate boiling heat transfer in the horizontal orientation (microcavities are vertical) were also investigated. Results indicated that, in general, increasing the number of micro cavities also increase the enhanced surface area and it could increase the critical heat flux. The pronounced increase of boiling heat transfer coefficients with the application of the artificial micro-cavity to the heat surface were also investigated in this paper.

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