Superheat Layer Thickness Measurements in Saturated and Subcooled Nucleate Boiling

1971 ◽  
Vol 93 (4) ◽  
pp. 455-461 ◽  
Author(s):  
J. R. Wiebe ◽  
R. L. Judd
Keyword(s):  
Mathematical Model ◽  
Experimental Study ◽  
Heat Flux ◽  
Layer Thickness ◽  
Glass Surface ◽  
Nucleate Boiling ◽  
Copper Surface ◽  
Bubble Nucleation ◽  
Temperature Profiles ◽  
Thickness Measurements

An experimental study of temperature profiles in water boiling on a horizontal copper surface is reported for incipient boiling conditions and for 20,000, 50,000, and 100,000 Btu/hr-ft2 heat flux at various levels of subcooling ranging from 0 to 105 deg F. The extrapolated superheat layer thickness results for the incipient boiling conditions lend support to Hsu’s mathematical model for bubble nucleation. Increasing heat flux and decreasing subcooling were observed to result in a decreasing extrapolated superheat layer thickness. Analysis of some additional results for Freon-113 boiling on a glass surface indicated that the thickness of the extrapolated superheat layer was governed by the bubble flux density which was influenced by both heat flux and subcooling.

An Experimental Investigation of the Effect of Subcooling on Bubble Growth and Waiting Time in Nucleate Boiling

1985 ◽  
Vol 107 (1) ◽  
pp. 168-174 ◽  
Author(s):  
E. A. Ibrahim ◽  
R. L. Judd
Keyword(s):  
Heat Flux ◽  
Waiting Time ◽  
Bubble Growth ◽  
Nucleate Boiling ◽  
Copper Surface ◽  
Growth Theory ◽  
Growth Time ◽  
Time Data ◽  
Relationship Of ◽  
Different Levels

The effect of subcooling on bubble waiting time and growth time for water boiling on a copper surface was examined in conjunction with measurements obtained over a range of subcooling from 0 to 15°C and three different levels of heat flux 166, 228, and 291 kW/m2. The growth-time data was successfully correlated with a model that combined the bubble growth theory of Mikic, Rohsenow, and Griffith with the bubble departure diameter relationship of Staniszewski, thereby establishing confidence in the measuring procedure. The waiting time data agreed with the predictions of the Han and Griffith waiting time theory at lower levels of subcooling but then showed a behavior contrary to that predicted for higher levels of subcooling.

A Photographic Study on the Effects of Hydrophobic-Spot Size and Subcooling on Local Film Boiling

2013 ◽  
Author(s):  
Bambang Joko Suroto ◽  
Masahiro Tashiro ◽  
Sana Hirabayashi ◽  
Sumitomo Hidaka ◽  
Masamichi Kohno ◽  
...  
Keyword(s):  
Heat Flux ◽  
High Speed ◽  
Bubble Dynamics ◽  
Pure Water ◽  
Nucleate Boiling ◽  
Spot Size ◽  
Copper Surface ◽  
Film Boiling ◽  
Working Fluid ◽  
Boiling Regime

The effects of hydrophobic circle spot size and subcooling on local film boiling phenomenon from the copper surface with single PTFE (Polytetrafluoroethylene) hydrophobic circle spot at low heat flux has been investigated. The experiments were performed using pure water as the working fluid and subcooling ranging from 0 and 10K. The heat transfer surfaces are used polished copper block with single PTFE hydrophobic circle spot of diameters 2, 4 and 6 mm, respectively. A high-speed camera was used to capture bubble dynamics and disclosed the sequence of the process leading to local film boiling. The result shows that local films boiling occurs on the PTFE circle spot at low heat flux and was triggered by the merging of neighboring bubbles. The study also showed that transition time required for change from nucleate boiling regime to local film boiling regime depends on the diameter of the hydrophobic circle spot and the subcooling. A stable local film boiling occurs at the smallest diameter of hydrophobic spot. Subcooling cause the local film boiling occur at negative superheat and oscillation of bubble dome.

Nucleate Boiling of Dielectric Liquids on Hydrophobic Patterned Surfaces

2014 ◽  
Author(s):  
Nihal E. Joshua ◽  
Denesh K. Ajakumar ◽  
Huseyin Bostanci
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Nucleate Boiling ◽  
High Heat ◽  
Copper Surface ◽  
Dielectric Liquid ◽  
Working Fluid ◽  
Patterned Surfaces ◽  
High Heat Flux ◽  
Dielectric Liquids

This study experimentally investigated the effect of hydrophobic patterned surfaces in nucleate boiling heat transfer. A dielectric liquid, HFE-7100, was used as the working fluid in the saturated boiling tests. Dielectric liquids are known to have highly-wetting characteristics. They tend to fill surface cavities that would normally trap vapor/gas, and serve as active nucleation sites during boiling. With the lack of these vapor filled cavities, boiling of a dielectric liquid leads to high incipience superheats and accompanying temperature overshoots. Heater samples in this study were prepared by applying a thin Teflon (AF400, Dupont) coating on 1-cm2 smooth copper surfaces following common photolithography techniques. Matching size thick film resistors, attached onto the copper samples, generated heat and simulated high heat flux electronic devices. Tests investigated the heater samples featuring circular pattern sizes between 40–100 μm, and corresponding pitch sizes between 80–200 μm. Additionally, a plain, smooth copper surface was tested to obtain reference data. Based on data, hydrophobic patterned surfaces effectively eliminated the temperature overshoot at boiling incipience, and considerably improved nucleate boiling performance in terms of heat transfer coefficient and critical heat flux over the reference surface. Hydrophobic patterned surfaces therefore demonstrated a practical surface modification method for heat transfer enhancement in immersion cooling applications.

Steady-State Subcooled Nucleate Boiling on a Downward-Facing Hemispherical Surface

1998 ◽  
Vol 120 (2) ◽  
pp. 365-370 ◽  
Author(s):  
K. H. Haddad ◽  
F. B. Cheung
Keyword(s):  
Heat Flux ◽  
Steady State ◽  
Heat Transport ◽  
Bubble Dynamics ◽  
Flow Direction ◽  
Heating Surface ◽  
Nucleate Boiling ◽  
High Heat ◽  
Bubble Nucleation ◽  
High Heat Flux

Steady-state nucleate boiling heat transfer experiments in saturated and subcooled water were conducted. The heating surface was a 0.305 m hemispherical aluminum vessel heated from the inside with water boiling on the outside. It was found that subcooling had very little effect on the nucleate boiling curve in the high heat flux regime where latent heat transport dominated. On the other hand, a relatively large effect of subcooling was observed in the low-heat-flux regime where sensible heat transport was important. Photographic records of the boiling phenomenon and the bubble dynamics indicated that in the high-heat-flux regime, boiling in the bottom center region of the vessel was cyclic in nature with a liquid heating phase, a bubble nucleation and growth phase, a bubble coalescence phase, and a large vapor mass ejection phase. At the same heat flux level, the size of the vapor masses was found to decrease from the bottom center toward the upper edge of the vessel, which was consistent with the increase observed in the critical heat flux in the flow direction along the curved heating surface.

Effects of UV-Visible Irradiation on Pool Boiling Behavior of Copper

2011 ◽  
Author(s):  
Chad N. Hunter ◽  
Nicholas R. Glavin ◽  
Andrey A. Voevodin ◽  
David B. Turner ◽  
Michael H. Check ◽  
...  
Keyword(s):  
Heat Flux ◽  
Light Source ◽  
Light Exposure ◽  
Nucleate Boiling ◽  
Copper Surface ◽  
Exposed Region ◽  
Surface Oxide Formation ◽  
Visible Irradiation ◽  
Uv Visible ◽  
Nanoscale Features

Roughened copper substrates were exposed to a broadband UV-VIS light source during nucleate boiling at a heat flux of 60–70% of the amount expected to result in critical heat flux (CHF) without exposure to a light source. The surface temperature decreased by 0.5–1.0°C within minutes after the UV-VIS light exposure began. CHF occurred after less than 20 minutes of exposure to the light source. Nanoscale features were observed in the light-exposed region of the copper surface after boiling, which were primarily associated with formation of Cu2O. The induced CHF likely occurred due to surface oxide formation, a resultant decrease in wettability of the surface.

EFFECT OF SURFACE WETTABILITY ON POOL BOILING: ENHANCEMENT BY HYDROPHOBIC COATING

2012 ◽  
Vol 20 (01) ◽  
pp. 1150003 ◽  
Author(s):  
YASUYUKI TAKATA ◽  
SUMITOMO HIDAKA ◽  
MASAMICHI KOHNO
Keyword(s):  
Heat Transfer ◽  
Pool Boiling ◽  
Nucleate Boiling ◽  
Copper Surface ◽  
Bubble Nucleation ◽  
Heat Transfer Surface ◽  
Water Repellent ◽  
Uniform Size ◽  
Hydrophobic Coating ◽  
Ptfe Surface

Pool boiling from a super-water-repellent (SWR) and polytetrafluoroethylene (PTFE) surface with checkered and spotted patterns has been studied experimentally. The heat transfer surfaces are copper with the SWR coating of checkered and spotted patterns and TiO2 -coated surface with PTFE spotted patterns. The domain of SWR and PTFE acts as nucleation sites and, therefore, bubble nucleation starts at very low superheating. In lower heat flux, bubbles with uniform size are generated on the SWR or PTFE domain of the heat transfer surface. These bubbles depart from the heat transfer surface when the contact line reaches the boundary of SWR or PTFE domain. Nucleate boiling with this surface was enhanced by seven times compared with the normal copper surface. The best was the spotted PTFE surface coated on TiO2 superhydrophilic surface.

Bubble Ebullition on a Hydrophilic Surface

2015 ◽  
Vol 137 (2) ◽  
Author(s):  
Aritra Sur ◽  
Yi Lu ◽  
Carmen Pascente ◽  
Paul Ruchhoeft
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Boiling Heat Transfer ◽  
High Speed ◽  
Nucleate Boiling ◽  
Bubble Nucleation ◽  
Working Fluid ◽  
Hydrophilic Surface ◽  
Nucleate Boiling Heat Transfer ◽  
Nucleate Bubble

Nucleate boiling heat transfer depends on various aspects of the bubble ebullition, such as the bubble nucleation, growth and departure. In this work, a synchronized high-speed optical imaging and infrared (IR) thermography approach was employed to study the ebullition process of a single bubble on a hydrophilic surface. The boiling experiments were conducted at saturated temperature and atmospheric pressure conditions. De-ionized (DI) water was used as the working fluid. The boiling device was made of a 385-um thick silicon wafer. A thin film heater was deposited on one side, and the other side was used as the boiling surface. The onset of nucleate boiling (ONB) occurs at a wall superheat of ΔTsup= 12 °C and an applied heat flux of q" = 35.9 kW/m2. The evolution of the wall heat flux distribution was obtained from the IR temperature measurements, which clearly depicts the existence of the microlayer near the three-phase contact line of the nucleate bubble. The results suggest that, during the bubble growth stage, the evaporation in the microlayer region contributes dominantly to the nucleate boiling heat transfer; however, once the bubble starts to depart from the boiling surface, the microlayer quickly vanishes, and the transient conduction and the microconvection become the prevailing heat transfer mechanisms.

Effects of Heater Material and Surface Orientation on Heat Transfer Coefficient and Critical Heat Flux of Nucleate Boiling

2017 ◽  
Author(s):  
Yong Mei ◽  
Yechen Zhu ◽  
Botao Zhang ◽  
Shengjie Gong ◽  
Hanyang Gu
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Boiling Heat Transfer ◽  
Orientation Angle ◽  
Nucleate Boiling ◽  
Copper Surface ◽  
Surface Orientation ◽  
Reactor Vessel

External reactor vessel cooling (ERVC) is the key technology for In-Vessel Retention (IVR) to ensure the safety of a nuclear power plant (NPP) under severe accident conditions. The thermal margin of nucleate boiling heat transfer on the reactor pressure vessel (RPV) lower head is important for ERVC and of wide concern to researchers. In such boiling heat transfer processes, the reactor vessel wall inclination effect on the heat transfer coefficient (HTC) and critical heat flux (CHF) should be considered. In this study, experiments were performed to investigate the effects of heater material and surface orientation on the HTC and CHF of nucleate boiling. Copper and stainless steel (SS) surfaces were used to perform boiling tests under atmosphere pressure. The orientation angle of both boiling surfaces were varied between 0° (upward) and 180° (downward). The experimental results show that the surface orientation effects on the HTC is slight for both the copper surface and the SS surface. In addition, the relationship of measured CHF values with the inclination angles was obtained and it shows that the CHF value changes little as the inclination angle increases from 0° to 120° but it decreases rapidly as the orientation angle increases towards 180° for both boiling surfaces. The material effect on CHF is also observed and the copper surface has higher CHF value than the SS surface. Based on the experimental data, a correlation for CHF prediction is developed which includes both the surface orientation effect and the heater material effect.

scholarly journals An experimental study on the subcooled flow boiling pressure drop of R141b in the system of two microchannels

2021 ◽  
Vol 2119 (1) ◽  
pp. 012053
Author(s):  
A. S. Shamirzaev
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Heat Flux ◽  
Pressure Drop ◽  
Flow Boiling ◽  
Nucleate Boiling ◽  
Copper Block ◽  
Subcooled Flow Boiling ◽  
Subcooled Flow ◽  
Boiling Incipience

Abstract An experimental study of the pressure drop under subcooled flow boiling of the refrigerant R141b in a system with two slotted microchannels was carried out. A copper block with two microchannels 2 mm wide, 0.4 mm deep, and 16 mm long was used as an experimental section for testing. The mass flow rate varied in the range from 1 to 4 g/s, the initial subcooling from 20°C to 50°C. Experimental data show a significant decrease in the pressure drop when the critical heat flux is reached. The experimental data are compared with the model known from the literature. Experimental data show that the occurrence of nucleate boiling incipience at subcooled boiling corresponds to a larger heat flux than that given by the recommended correlation.

Bubbles Transient Growth in Saturation Boiling of PF-5060 Dielectric Liquid on Dimpled Cu Surfaces

2016 ◽  
Vol 8 (2) ◽  
Author(s):  
Arthur Suszko ◽  
Mohamed S. El-Genk
Keyword(s):  
Heat Flux ◽  
Bubble Diameter ◽  
Nucleate Boiling ◽  
Bubble Nucleation ◽  
Dielectric Liquid ◽  
Growth Time ◽  
Transient Growth ◽  
Vapor Bubbles ◽  
Volumetric Growth ◽  
Video Images

Investigated is the transient growth of vapor bubbles in saturation boiling of PF-5060 dielectric liquid on 10 × 10 mm, uniformly heated Cu surfaces with circular dimples, at an applied heat flux of 0.5 W/cm2. At such low heat flux, the surfaces are populated with growing discrete bubbles, emanating mostly from the manufactured dimples. The 300, 400, and 500 μm diameter and 200 μm deep dimples are manufactured in a triangular lattice with a pitch-to-diameter ratio of 2.0; thus, the total number of dimples increases with decreasing the dimple diameter. Captured video images of growing discrete bubbles at a speed of 210 frames per second (fps) confirm that the bubble diameter increases proportional to the square root of the growth time, and the bubble departure diameter and detachment frequency increase with increasing the dimple diameter. The total volumetric growth rate and diameter of the bubbles at departure increase with increasing the dimple diameter, ∼1.81, ∼4.75, and ∼8.2 mm3/s and ∼738 μm, ∼963 μm, and ∼1051 μm for the 300, 400, and 500 μm diameter dimples, respectively. The corresponding bubble detachment frequency is ∼8.6 Hz, ∼10.2 Hz, and ∼13.5 Hz, respectively. The fraction of the active dimples for bubble nucleation on the surfaces with 300, 400, and 500 μm dimples, at an applied heat flux of 0.5 W/cm2, is ∼0.85, ∼0.64, and ∼0.53, respectively. On these surfaces, the estimated bubble volume at departure is ∼0.21 mm3, ∼0.47 mm3, and ∼0.61 mm3, and the corresponding rate of energy removed by a single bubble is ∼1.99 mW, ∼5.24 mW, and ∼9.02 mW, respectively. These results help explain the measured enhancements in nucleate boiling and the critical heat flux (CHF) on the dimpled Cu surfaces.

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