Heat Transfer to Pool-Boiling Mercury From Horizontal Cylindrical Heaters at Heat Fluxes up to Burnout

1971 ◽  
Vol 93 (1) ◽  
pp. 1-10 ◽  
Author(s):  
J. Brent Turner ◽  
C. Phillip Colver
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Stainless Steel ◽  
Pool Boiling ◽  
Heat Fluxes ◽  
Boiling Curve ◽  
304 Stainless Steel ◽  
Pool Depth ◽  
Flux Level

Reproducible and consistent data were obtained for heat transfer to pool-boiling mercury from horizontal, 304 stainless steel, cylindrical heaters at heat fluxes up to 1,100,000 Btu/hr· ft2. One actual burnout determination was made during the course of the study. In other runs, a heat-flux level was reached where the slope of the boiling curve decreased significantly so that subsequent increases in heat flux were accompanied by large increases in ΔT. This heat-flux level was termed the “departure heat flux.” Observed maximum departure heat fluxes ranged from 400,000 Btu/hr·ft2 for a 2-in. pool depth above the heater to 950,000 Btu/hr·ft2 for an 8.5-in. depth. The burnout correlations of Noyes [17, 22] and Addoms [1] satisfactorily predicted the maximum departure heat fluxes for each pool depth studied.

Observations of the Critical Heat Flux Process During Pool Boiling of FC-72

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
J. Jung ◽  
S. J. Kim ◽  
J. Kim
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Pool Boiling ◽  
High Heat ◽  
Line Length ◽  
Boiling Curve ◽  
High Heat Flux ◽  
Transfer Coefficients ◽  
Ir Camera

Experimental work was undertaken to investigate the process by which pool-boiling critical heat flux (CHF) occurs using an IR camera to measure the local temperature and heat transfer coefficients on a heated silicon surface. The wetted area fraction (WF), the contact line length density (CLD), the frequency between dryout events, the lifetime of the dry patches, the speed of the advancing and receding contact lines, the dry patch size distribution on the surface, and the heat transfer from the liquid-covered areas were measured throughout the boiling curve. Quantitative analysis of this data at high heat flux and transition through CHF revealed that the boiling curve can simply be obtained by weighting the heat flux from the liquid-covered areas by WF. CHF mechanisms proposed in the literature were evaluated against the observations.

Measuring Heat Transfer From Firebrands to Surfaces

2020 ◽  
Author(s):  
Elias Bearinger ◽  
Brian Lattimer ◽  
Jonathan Hodges ◽  
Christian Rippe
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Stainless Steel ◽  
Steel Plate ◽  
Radiant Energy ◽  
Heat Fluxes ◽  
Quartz Plate ◽  
Steel Plates ◽  
Inverse Heat Transfer ◽  
Flux Measurements

Abstract Firebrands are an important mechanism of fire spread and one of the primary ways in which wildland fires ignite structures. Inverse heat transfer using thin steel plates has been shown to be an effective method for measuring heat transfer distributions from firebrands. To fully understand the dynamic process of heat transfer from firebrands to surfaces; however, it is necessary to view the underside of the firebrands, which is not possible through a steel plate. This work develops a method of inverse heat transfer using a visually transparent quartz plate and a long-wave (7.5–14.0 μm) infrared camera to facilitate visual access to the firebrands from all angles. The heat flux measurements using a quartz plate were compared with heat flux measurements using a steel plate and finite element heat transfer simulations for radiation-dominant tests using heater panels. Additionally, heat transfer measurements using cuboidal oak firebrands were conducted using both the quartz and steel plates. A corrective factor was developed based on the ratio of the effective emissivity of the quartz and stainless-steel plates at typical firebrand temperatures. The measured heat fluxes were within 1–6% after correcting for radiant energy transmitted through the quartz which was absorbed by the stainless-steel plate.

Pool boiling performance of oxide nanofluid on a downward-facing heating surface

Kerntechnik ◽  
2022 ◽  
Vol 0 (0) ◽  
Author(s):  
Zhibo Zhang ◽  
Huai-En Hsieh ◽  
Yuan Gao ◽  
Shiqi Wang ◽  
Jia Gao ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Surface Roughness ◽  
Stainless Steel ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Critical Heat Flux ◽  
Pool Boiling ◽  
Heating Surface ◽  
Nano Particles

Abstract In this study, the pool boiling performance of oxide nanofluid was investigated, the heating surface is a 5 × 30 mm stainless steel heating surface. Three kinds of nanofluids were selected to explore their critical heat flux (CHF) and heat transfer coefficient (HTC), which were TiO2, SiO2, Al2O3. We observed that these nanofluids enhanced CHF compared to R·O water, and Al2O3 case has the most significant enhancement (up to 66.7%), furthermore, the HTC was also enhanced. The number of bubbles in nanofluid case was relatively less than that in R·O water case, but the bubbles were much larger. The heating surface was characterized and it was found that there were nano-particles deposited, and surface roughness decreased. The wettability also decreased with the increase in CHF.

An Experimental Study of Miniature-Scale Pool Boiling

2003 ◽  
Vol 125 (6) ◽  
pp. 1074-1086 ◽  
Author(s):  
Tailian Chen ◽  
Jacob N. Chung
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Pool Boiling ◽  
Heat Fluxes ◽  
Boiling Curve ◽  
Feedback Control System ◽  
Electronic Feedback ◽  
Fundamental Understanding ◽  
Peak Heat Flux ◽  
Different Temperatures

By generating single bubbles on a micro-heater at different wall superheats, an experimental study of miniature-scale pool boiling heat transfer has been performed to provide a fundamental understanding of the heater size effect. In this study, the constant-temperature microheater is set at different temperatures by an electronic feedback control system. The heat transfer history during the lifetime of a single bubble which includes nucleation, growth, detachment and departure has been measured. The boiling curve obtained from the microheater is composed of two regimes which are separated by a peak heat flux. It is suggested that in the lower superheat regime, the boiling is dominated by liquid rewetting and micro-layer evaporation, while in the higher superheat regime, conduction through the vapor film and micro-convection plays the key heat transfer role as the heater is covered by vapor all the time. In general, boiling on microheaters is characterized by larger bubble departure sizes, smaller bubble growth rates due to the dryout of microlayer as the bubble grows, and higher bubble incipience superheat. As the heater size decreases, the boiling curve shifts towards higher heat fluxes with corresponding higher superheats.

Boiling Heat Transfer in a Shallow Fluidized Particulate Bed

1987 ◽  
Vol 109 (1) ◽  
pp. 196-203 ◽  
Author(s):  
Y. K. Chuah ◽  
V. P. Carey
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Flux ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Thin Layers ◽  
Surface Nucleation ◽  
Particle Layer ◽  
Wall Superheat ◽  
Flux Level

Experimental data are presented which indicate the effects of a thin layer of unconfined particles on saturated pool boiling heat transfer from a horizontal surface. Results are presented for two different types of particles: (1) 0.275 and 0.475-mm-dia glass spheres which have low density and thermal conductivity, and (2) 0.100 and 0.200-mm-dia copper spheres which have high density and thermal conductivity. These two particle types are the extremes of particles found as corrosion products or contaminants in boiling systems. To ensure that the surface nucleation characteristics were well defined, polished chrome surfaces with a finite number of artificial nucleation sites were used. Experimental results are reported for heat fluxes between 20 kW/m2 and 100kW/m2 using water at 1 atm as a coolant. For both particle types, vapor was observed to move upward through chimneys in the particle layer, tending to fluidize the layer. Compared with ordinary pool boiling at the same surface heat flux level, the experiments indicate that addition of light, low-conductivity particles significantly increases the wall superheat, whereas addition of heavier, high-conductivity particles decreases wall superheat. Heat transfer coefficients measured in the experiments with a layer of copper particles were found to be as much as a factor of two larger than those measured for ordinary pool boiling at the same heat flux level. The results further indicate that at least for thin layers, the boiling curve is insensitive to layer thickness. These results are shown to be consistent with the expected effects of the particles on nucleation, fluid motion, and effective conductivity in the pool at or near the surface. The effect of surface nucleation site density on heat transfer with a particle layer present is also discussed.

Pressure influence on saturated boiling of R141b over Cu and Si-coated surfaces

2021 ◽  
pp. 095440892110452
Author(s):  
Abhishek Swarnkar ◽  
Vikas J. Lakhera
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Heat Flux ◽  
Pressure Range ◽  
Pool Boiling ◽  
Heat Fluxes ◽  
Working Fluid ◽  
Operating Pressure ◽  
Coated Surface ◽  
Coated Surfaces

Pool boiling has been a research topic of great interest over the decades due to its inherent capabilities of large heat transfer rates with narrow temperature gaps and it advocates its suitability in a large number of industrial applications. The present paper describes the effect of operating pressure on pool boiling of R141b over a plain Cu surface as well as Si-coated surface prepared by a direct current (DC) sputtering technique. The working fluid R141b undergoes saturated pool boiling under pressure ranging from −20 kPa(g) to + 30 kPa(g) with the acquired experimental data and trends compared with the existing correlations and theories. Within the pressure range considered, the surface superheat variation was insignificant at lower heat fluxes; however, at higher heat fluxes, the maximum reduction was found to be by 9.5°C and 14.8°C for the plain Cu surface and Si-coated surface, respectively, regarding the corresponding values of −20 kPa(g) pressure. With respect to the results under atmospheric conditions, at the pressure of + 30 kPa(g), a corresponding increase in heat transfer coefficient of 12.1% for the plain Cu surface and of 17.8% for a Si-coated surface was observed at a heat flux of 225 kW/m2 and 272 kW/m2, respectively. In comparison to the results under atmospheric pressure conditions, the accompanying augmentation in the critical heat flux was observed as 13.3% for the plain Cu and 21.2% for the Si-coated surfaces at a pressure of + 30 kPa(g). Based on the experimental data, a correlation is developed for predicting heat transfer coefficients within the given pressure range.

Experimental Study of Heat Transfer Enhancement in Pool Boiling by Using 2-Ethyl 1-Hexanol an Additive

2014 ◽  
Vol 592-594 ◽  
pp. 1601-1606 ◽  
Author(s):  
Sameer Sheshrao Gajghate ◽  
Anil R. Aacharya ◽  
Anil T. Pise ◽  
Ganesh S. Jadhav
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Boiling Heat Transfer ◽  
Bubble Dynamics ◽  
Pool Boiling ◽  
Nucleate Boiling ◽  
Heat Fluxes ◽  
Optimum Level ◽  
Transfer Coefficients ◽  
Nichrome Wire

The addition of additives to the water is known to enhance boiling heat transfer. In the present investigation, boiling heat transfer coefficients are measured for Nichrome wire, immersed in saturated water with & without additive. An additive used is 2-Ethyl 1-Hexanol with varying concentrations in the range of 10-10000 ppm. Extensive experimentation of pool boiling is carried out above the critical heat flux. Boiling behavior i.e. bubble dynamics are observed at higher heat flux for nucleate boiling of water over wide ranges of concentration of additive in water. Results are encouraging and show that a small amount of surface active additive makes the nucleate boiling heat transfer coefficient considerably higher, and that there is an optimum additive (500-1000ppm) concentration for higher heat fluxes. An optimum level of enhancement is observed up to a certain amount of additive 500-1000ppm in the tested range. Thereafter significant enhancement is not observed. This enhancement may be due to change in thermo-physical properties i.e. mainly due to a reduction in surface tension of water in the presence of additive.

scholarly journals Heat transfer and critical heat flux for two-phase immersion cooling of an inverter power module

2021 ◽  
Vol 2116 (1) ◽  
pp. 012007
Author(s):  
I T’ Jollyn ◽  
J Nonneman ◽  
M De Paepe
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Pool Boiling ◽  
Flux Measurement ◽  
Base Plate ◽  
Heat Fluxes ◽  
Power Module ◽  
Two Phase ◽  
Heat Flux Measurement

Abstract Heat transfer and critical heat flux measurement are reported for pool boiling cooling of the base plate of an inverter power module. Novec 649 is used as refrigerant. Heat fluxes up to 14.6 W/cm2 were applied with refrigerant saturation temperatures of 36 °C, 41 °C and 46 °C. The measured boiling curves are comparable to those reported for similar refrigerants. The critical heat fluxes range from 12.1 W/cm2 to 14.6 W/cm2, which corresponds within 10% to the correlation of Zuber. The critical heat flux is significantly lower than the highest heat fluxes expected from the power module, indicating that methods to increase the critical heat flux are needed to enable two-phase power module cooling.

scholarly journals Effects of Surface Conditions on Nucleate Pool Boiling of Sodium

1966 ◽  
Vol 88 (2) ◽  
pp. 196-203 ◽  
Author(s):  
P. J. Marto ◽  
W. M. Rohsenow
Keyword(s):  
Pool Boiling ◽  
Nucleate Boiling ◽  
Heat Fluxes ◽  
Boiling Curve ◽  
Porous Coatings ◽  
Surface Conditions ◽  
Effect Of Pressure ◽  
Pool Depth ◽  
Commercial Grade ◽  
Surface Finishes

Commercial grade sodium was boiled from a horizontal disk at pressures of 65 mm, 200 mm, and 400 mm Hg absolute, with sodium temperatures ranging from 1200 F to 1500 deg F. Heat fluxes as high as 236,000 Btu/hr sq ft were attained. Boiler surface finishes ranged from highly polished mirror finishes to coarse, porous coatings. By following a prescribed cleaning and filling procedure, nucleate-boiling results were generally reproducible for a given-type surface. The effect of roughness as well as any aging and hysteresis effects were experimentally determined. Incipient nucleate boiling results are discussed as well as the effect of pressure and pool depth on the nucleate-boiling curve.

Nucleate boiling heat transfer coefficients of halogenated refrigerants up to critical heat fluxes

2009 ◽  
Vol 223 (6) ◽  
pp. 1415-1424 ◽  
Author(s):  
K-J Park ◽  
D Jung ◽  
S E Shim
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Nucleate Boiling ◽  
Heat Fluxes ◽  
Nucleate Pool Boiling ◽  
Transfer Coefficients ◽  
Average Deviation ◽  
Heat Transfer Coefficients

In this work, nucleate pool boiling heat transfer coefficients (HTCs) of five refrigerants of differing vapour pressures are measured on a horizontal, smooth copper surface of 9.53×9.53 mm. The tested refrigerants are R123, R152a, R134a, R22, and R32 and HTCs are taken from 10 kW/m2 to the critical heat flux (CHF) of each refrigerant. Wall and fluid temperatures are measured directly by thermocouples located underneath the test surface and in the liquid pool, respectively. Test results show that nucleate pool boiling HTCs of halogenated refrigerants increase as the heat flux and vapour pressure increase. This typical trend is maintained even at high heat fluxes above 200 kW/m2. Zuber's prediction equation for CHF is quite accurate showing a maximum deviation of 21 per cent for all refrigerants tested. For all refrigerants, Stephan and Abdelsalam's well-known correlation underpredicted nucleate boiling HTC data up to the CHF with an average deviation of 21.3 per cent, while Cooper's correlation overpredicted the data with an average deviation of 14.2 per cent. On the other hand, Gorenflo's and Jung et al.'s correlations showed 5.8 and 6.4 per cent deviations, respectively, in the entire nucleate boiling range up to the CHF.

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