An Induced-Convection Effect Upon the Peak-Boiling Heat Flux

1970 ◽  
Vol 92 (1) ◽  
pp. 1-5 ◽  
Author(s):  
J. H. Lienhard ◽  
K. B. Keeling
Keyword(s):  
Heat Flux ◽  
Pool Boiling ◽  
Reduced Pressure ◽  
Flux Data ◽  
Peak Heat Flux ◽  
Variable Gravity

An induced-convection effect upon the peak pool-boiling heat flux is identified and described. A method is developed for correlating this effect under conditions of variable gravity, pressure and size, as well as for various boiled liquids. The effect is illustrated, and the correlation verified, with a large number of peak heat-flux data obtained on a horizontal ribbon heater. The data, obtained in a centrifuge, embrace an 87-fold range of gravity, a 22-fold range of width, a 15-fold variation of reduced pressure, and five liquids.

Gravity Scaling Parameter for Pool Boiling Heat Transfer

2010 ◽  
Vol 132 (9) ◽  
Author(s):  
Rishi Raj ◽  
Jungho Kim ◽  
John McQuillen
Keyword(s):  
Heat Flux ◽  
Pool Boiling ◽  
Gravity Level ◽  
Dissolved Gas ◽  
Experimental Conditions ◽  
Scaling Parameter ◽  
Flux Data ◽  
Earth Gravity ◽  
Variable Gravity ◽  
Continuous Range

Although the effects of microgravity, earth gravity, and hypergravity (>1.5 g) on pool boiling heat flux have been studied previously, pool boiling heat flux data over a continuous range of gravity levels (0–1.7 g) was unavailable until recently. The current work uses the results of a variable gravity, subcooled pool boiling experiment to develop a gravity scaling parameter for n-perfluorohexane/FC-72 in the buoyancy-dominated boiling regime (Lh/Lc>2.1). The heat flux prediction was then validated using heat flux data at different subcoolings and dissolved gas concentrations. The scaling parameter can be used as a tool to predict boiling heat flux at any gravity level in the buoyancy dominated regime if the data under similar experimental conditions are available at any other gravity level.

Gravity Scaling Parameter for Pool Boiling Heat Transfer

2009 ◽  
Author(s):  
Rishi Raj ◽  
Jungho Kim ◽  
John McQuillen
Keyword(s):  
Heat Flux ◽  
Pool Boiling ◽  
Gravity Level ◽  
Low Gravity ◽  
Experimental Conditions ◽  
Scaling Parameter ◽  
Flux Data ◽  
Variable Gravity ◽  
Continuous Range ◽  
Good Agreement

The effect of low gravity on pool boiling heat flux has been studied by researchers, but pool boiling heat flux data over a continuous range of gravity levels (0g–1.8g) was unavailable until recently. The current work uses the results of a variable gravity subcooled pool boiling experiment to develop a gravity scaling parameter for prediction purposes. The heat flux prediction at various gravity levels was found to be in good agreement with the measured heat flux data. The scaling parameter can be used as a tool to predict boiling heat flux at any gravity level if the data under similar experimental conditions are available at any other gravity level. The scaling parameter has been demonstrated to be valid for pool boiling of n-perfluorohexane in heater size independent boiling regime (Lh/Lc>2.8).

Peak Pool Boiling Heat Flux in Viscous Liquids

1974 ◽  
Vol 96 (1) ◽  
pp. 71-78 ◽  
Author(s):  
V. K. Dhir ◽  
J. H. Lienhard
Keyword(s):  
Heat Flux ◽  
Viscous Liquid ◽  
Critical Velocity ◽  
Functional Form ◽  
Pool Boiling ◽  
Gas Jet ◽  
Flat Plates ◽  
Viscous Liquids ◽  
Peak Heat Flux ◽  
The Stability

The stability of a gas jet in a surrounding viscous liquid is studied. An expression is developed for the critical velocity at which the jet becomes unstable in a returning viscous liquid. The stability analysis is made to correspond with the geometrical configuration of gas jets and liquid columns similar to those observed near the peak pool boiling heat flux. The critical velocity of the gas jet is then used to obtain the functional form of the peak heat flux on flat plates and cylindrical heaters. The expressions are compared with original observations of the peak heat flux in very viscous liquids on flat plate, and cylindrical, heaters at both earth-normal, and elevated, gravities.

Rewetting Velocity of High-Temperature Vertical-Narrow-Annular Flow Passages Under Counter-Current Flow Condition

2003 ◽  
Author(s):  
Yasuo Koizumi ◽  
Hiroyasu Ohtake ◽  
Masanori Tsukudo ◽  
Naoki Sakamoto
Keyword(s):  
Heat Flux ◽  
Annular Flow ◽  
Pool Boiling ◽  
Outer Wall ◽  
Heat Fluxes ◽  
Annular Gap ◽  
Wall Superheat ◽  
Peak Heat Flux ◽  
Inner Diameter ◽  
Counter Current

Quenching of a thin gap annular flow passage by gravitational liquid penetration was examined experimentally by using R-113. The outer wall was made of copper. The inner wall was made of copper or glass. The inner diameter of the outer wall of the annular flow passages was 40 or 41 mm and the annular gap clearance δ was 0.5, 1.0, 2.0 and 5.0 mm. The outer wall was heated initially up to 250 °C and also the inner wall was heated when the copper inner wall was used. The quenching was observed in δ ≥ 1.0 mm. When δ = 0.5 mm, the wall was just gradually cooled down. The relation between the wall superheat and the heat flux during quenching process was similar to the boiling curve of pool boiling. However, the peak heat flux as well as the heat flux in the film and the transition boiling was lower than those in the pool boiling. These heat fluxes became lower as the gap clearance became narrow. The rewetting velocity became slow as the gap clearance became narrow. The rewetting velocity seemed to have a unique relation for the Peclet number Pe = (ρSCSδSU/λS) and the Biot number Bi = hδs/λs ; Pe ∝ Bi which was the same as that of the Yamanouchi correlation. A decrease in the heat flux (the heat transfer coefficient) in the rewetting front region, which corresponds to the peak heat flux, results in a decrease in the rewetting velocity as the gap clearance becomes narrow.

Peak Pool Boiling Heat-Flux Measurements on Finite Horizontal Flat Plates

1973 ◽  
Vol 95 (4) ◽  
pp. 477-482 ◽  
Author(s):  
J. H. Lienhard ◽  
V. K. Dhir ◽  
D. M. Riherd
Keyword(s):  
Experimental Data ◽  
Heat Flux ◽  
Flat Plate ◽  
Pool Boiling ◽  
Heat Fluxes ◽  
Hydrodynamic Theory ◽  
Organic Liquids ◽  
Flat Plates ◽  
Peak Heat Flux ◽  
Flux Measurements

Experimental data obtained at both earth-normal and elevated gravity, in a variety of organic liquids and water, are used to verify the hydrodynamic theory for the peak pool boiling heat flux on flat plates. A modification of Zuber’s formula, which gives a 14 percent higher peak heat flux, is verified as long as the flat plate is more than three Taylor wavelengths across. For smaller heaters, the hydrodynamic theory requires a wide variation in heat flux owing to discontinuities in the number of escaping jets. Data for smaller plates bear out this predicted variation with heat fluxes that range between 40 percent and 235 percent of Zuber’s predicted value. Finally, a method is suggested for augmenting the peak heat flux on large heaters, and shown experimentally to be viable.

Hydrodynamic Prediction of Peak Pool-boiling Heat Fluxes from Finite Bodies

1973 ◽  
Vol 95 (2) ◽  
pp. 152-158 ◽  
Author(s):  
J. H. Lienhard ◽  
V. K. Dhir
Keyword(s):  
Heat Flux ◽  
Flat Plate ◽  
Pool Boiling ◽  
General Concept ◽  
Heat Fluxes ◽  
The Body ◽  
Cross Sectional ◽  
Vapor Velocity ◽  
General Ground ◽  
Peak Heat Flux

Since Zuber made a hydrodynamic prediction of the peak pool-boiling heat flux on an infinite flat plate, his general concept has been used to predict the peak heat flux in two finite heater configurations. These latter predictions have differed from Zuber’s in the introduction of a largely empirical variable—the thickness of the vapor escape path around the body. The present study shows how measurements of this thickness can be combined with the hypothesis that the vapor velocity within the vapor blanket must match the vapor velocity in the escaping jet above the heater. The result is a more exact description of the hydrodynamics of vapor removal. This idea is used to suggest the possibility of a universal value for the ratio of the cross-sectional area of escaping jets to the heater area for large finite heaters and for long slender heaters. A set of general ground rules is developed for predicting the peak heat fluxes on both large and small heaters. These rules are used in turn to predict the peak heat flux from horizontal ribbons. They are also used to correct the traditional prediction for infinite-flat-plate heaters. The predictions are supported with new data.

On Correlating the Peak and Minimum Boiling Heat Fluxes With Pressure and Heater Configuration

1966 ◽  
Vol 88 (1) ◽  
pp. 94-99 ◽  
Author(s):  
John H. Lienhard ◽  
Kiyokazu Watanabe
Keyword(s):  
Heat Flux ◽  
Pressure Range ◽  
Pool Boiling ◽  
Three Dimensional ◽  
Nucleate Boiling ◽  
Heat Fluxes ◽  
Reduced Pressure ◽  
Minimum Heat ◽  
Dimensional Surface ◽  
Horizontal Wire

The peak nucleate boiling heat flux has been observed for five fluids during saturated pool boiling on horizontal wire heaters, ranging in radius from 0.0025 in. to 0.0254 in., over a reduced pressure range from 0.0010 to 0.0197. A scheme for correlating the peak and minimum heat fluxes is developed heuristically and successfully applied to these data. The result is a single three-dimensional surface which represents all of the data. The surface can be represented as the product of a function of geometric scale, and a function of pressure. The function of pressure appears to be the same in any configuration.

scholarly journals Survey on the nucleate pool boiling of hydrogen and its limits

2020 ◽  
Vol 4 (2) ◽  
pp. 157-166
Author(s):  
Touhami Baki
Keyword(s):  
Experimental Data ◽  
Heat Flux ◽  
Low Temperature ◽  
Pool Boiling ◽  
Nucleate Boiling ◽  
Temperature Gradients ◽  
Nucleate Pool Boiling ◽  
Reduced Pressure ◽  
Predicted Values ◽  
Efficient Transfer

Nucleate pool boiling is a very efficient transfer regime with low temperature gradients, bounded between two heat flux values and which border transitions to other regimes, this phenomenon is well framed with correlations; our study aims to clarify the applicability of this regime to liquid hydrogen and to develop reliable correlations for a useful and qualitative agreement. An exhaustive review on the nucleate pool boiling of hydrogen and the limits of this regime, whether are the onset nucleate boiling (ONB) and the critical heat flux (CHF) was made, allowing the collection of more than 1400 points from experimental setups, highlighting a variety of parameters. Five predictive correlations were drawn from the literature, graphical and statistical comparisons were made, two in five reveal acceptable results. After analysis of the experimental data, new correlations were developed and compared with the data collected, convincing results were obtained and discussed. A simple form was expressed for the heat flux , shows better predicted values; convincing results of the (CHF) have been found on modified Kutateladze correlation (1948), and the CHF value reaches a maximum of 148×103 W/m² for a reduced pressure at 0.35; a nucleate boiling correlation suitable for hydrogen has been developed.

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