Film Boiling Heat Transfer on an Isothermal Vertical Surface

1985 ◽  
Vol 107 (4) ◽  
pp. 764-771 ◽  
Author(s):  
T. D. Bui ◽  
V. K. Dhir
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Large Scale ◽  
Heated Surface ◽  
Vertical Surface ◽  
Film Boiling ◽  
Small Scale ◽  
Vapor Film ◽  
Interfacial Wave ◽  
Transfer Coefficients

Natural convection film boiling heat transfer of saturated liquids on an isothermal vertical surface is investigated both experimentally and theoretically. Local heat transfer coefficients are obtained at steady-state conditions on a 6.3-cm-wide and 10.3-cm-high heated surface which was machined from a large block of copper. Effectively isothermal surface conditions are achieved even for wall superheats up to 450 K. Experiments conducted with water at 1 atm pressure show that predictions from existing theoretical models are inadequate and a detailed consideration of the liquid-vapor interface behavior is required. Still and motion pictures of the vapor film are taken and data on vapor film thickness, interfacial wave behavior, and bubble detachment characteristics are obtained to build an analytical model for predicting film boiling heat transfer. This time-dependent model based on laminar flow in the film incorporates the effects of both large-scale and small-scale waves. Results from analysis are compared with experimental data.

Pool Boiling Heat Transfer From Plain and Microporous, Square Pin Finned Surfaces in Saturated FC-72

1999 ◽  
Author(s):  
K. N. Rainey ◽  
S. M. You
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Large Scale ◽  
Pool Boiling ◽  
Nucleate Boiling ◽  
Small Scale ◽  
Surface Microstructure ◽  
Transfer Coefficients ◽  
Microporous Coating ◽  
Nucleate Boiling Heat Transfer

Abstract The present research is an experimental study of “double enhancement” behavior in pool boiling from heater surfaces simulating microelectronic devices immersed in saturated FC-72 at atmospheric pressure. The term “double enhancement” refers to the combination of two different enhancement techniques: a large-scale area enhancement (square pin fin array) and a small-scale surface enhancement (microporous coating). Fin lengths were varied from 0 (flat surface) to 8 mm. Effects of this double enhancement technique on critical heat flux (CHF) and nucleate boiling heat transfer in the horizontal orientation (fins are vertical) are investigated. Results showed significant increases in nucleate boiling heat transfer coefficients with the application of the microporous coating to the heater surfaces. CHF was found to be relatively insensitive to surface microstructure for the finned surfaces except in the case of the surface with 8 mm long fins. The nucleate boiling and CHF behavior has been found to be the result of multiple, counteracting mechanisms: surface area enhancement, fin efficiency, surface microstructure (active nucleation site density), vapor bubble departure resistance, and re-wetting liquid flow resistance.

Pool Boiling Heat Transfer From Plain and Microporous, Square Pin-Finned Surfaces in Saturated FC-72

2000 ◽  
Vol 122 (3) ◽  
pp. 509-516 ◽  
Author(s):  
K. N. Rainey ◽  
S. M. You
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Large Scale ◽  
Pool Boiling ◽  
Nucleate Boiling ◽  
Small Scale ◽  
Surface Microstructure ◽  
Transfer Coefficients ◽  
Microporous Coating ◽  
Nucleate Boiling Heat Transfer

The present research is an experimental study of “double enhancement” behavior in pool boiling from heater surfaces simulating microelectronic devices immersed in saturated FC-72 at atmospheric pressure. The term “double enhancement” refers to the combination of two different enhancement techniques: a large-scale area enhancement (square pin fin array) and a small-scale surface enhancement (microporous coating). Fin lengths were varied from 0 (flat surface) to 8 mm. Effects of this double enhancement technique on critical heat flux (CHF) and nucleate boiling heat transfer in the horizontal orientation (fins are vertical) are investigated. Results showed significant increases in nucleate boiling heat transfer coefficients with the application of the microporous coating to the heater surfaces. CHF was found to be relatively insensitive to surface microstructure for the finned surfaces except in the case of the surface with 8-mm-long fins. The nucleate boiling and CHF behavior has been found to be the result of multiple, counteracting mechanisms: surface area enhancement, fin efficiency, surface microstructure (active nucleation site density), vapor bubble departure resistance, and re-wetting liquid flow resistance. [S0022-1481(00)02603-7]

Liquid-Solid Contact During Flow Film Boiling of Subcooled Freon-11

1990 ◽  
Vol 112 (2) ◽  
pp. 465-471 ◽  
Author(s):  
K. H. Chang ◽  
L. C. Witte
Keyword(s):  
Heat Transfer ◽  
Large Scale ◽  
Heat Fluxes ◽  
Film Boiling ◽  
Small Scale ◽  
Solid Contact ◽  
Heated Cylinder ◽  
Experimental Heat ◽  
Wall Superheat ◽  
Flow Film Boiling

Liquid-solid contacts were measured for flow film boiling of subcooled Freon-11 over an electrically heated cylinder equipped with a surface microthermocouple probe. No systematic variation of the extent of liquid-solid contact with wall superheat, liquid subcooling, or velocity was detected. Only random small-scale contacts that contribute negligibly to overall heat transfer were detected when the surface was above the homogeneous nucleation temperature of the Freon-11. When large-scale contacts were detected, they led to an unexpected intermediate transition from local film boiling to local transition boiling. An explanation is proposed for these unexpected transitions. A comparison of analytical results that used experimentally determined liquid-solid contact parameters to experimental heat fluxes did not show good agreement. It was concluded that the available model for heat transfer accounting for liquid-solid contact is not adequate for flow film boiling.

Effect of Nanofluid on the Film Boiling Behavior at Vapor Film Collapse

2009 ◽  
Author(s):  
Takahiro Arai ◽  
Masahiro Furuya
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Direct Contact ◽  
Film Surface ◽  
Film Boiling ◽  
Vapor Film ◽  
Quenching Temperature ◽  
Steel Sphere ◽  
Film Collapse ◽  
Al2o3 Nanofluid

A high-temperature stainless-steel sphere was immersed into Al2O3 nanofluid to investigate film boiling heat transfer and collapse of vapor film. Surface temperature is referred to the measured value of thermocouples embedded into and welded onto a surface of the sphere. A direct contact between the immersed sphere and Al2O3 nanofluids is quantified by the acquired electric conductivity. The Al2O3 nanofluid concentration is varied from 0.024 to 1.3 vol%. A film boiling heat transfer rate of Al2O3 nanofluid is almost the same or slightly lower than that of water. A quenching temperature rises slightly with increased the Al2O3 nanofluid concentrations. In both water and Al2O3 nanofluid, the direct contact signals between the sphere and coolant were not detected before vapor film collapse.

Angular Dependency on Film Boiling Heat Transfer From Relatively Long Inclined Flat Plates

2013 ◽  
Vol 135 (12) ◽  
Author(s):  
Chan Soo Kim ◽  
Kune Y. Suh
Keyword(s):  
Heat Transfer ◽  
Flat Plate ◽  
Boiling Heat Transfer ◽  
Flow Direction ◽  
Film Boiling ◽  
Transfer Coefficients ◽  
Flat Plates ◽  
Heat Transfer Coefficients ◽  
Inclination Angles ◽  
Angular Dependency

The effect of inclination angle of the downward facing flat plate on the interfacial wavy motion is investigated utilizing the water quenching test apparatus downward ebullient laminar transition apparatus flat surface (DELTA-FS) in a quasi-steady state. Film boiling heat transfer coefficients are obtained on the relatively long surface in the flow direction. Interfacial velocities at the various inclination angles and wall superheat conditions are determined through the analysis of the visualized continuous snapshots with 1000 fps. Visualization of the vapor film reveals that the interfacial wavelength increases and the interfacial velocity decreases as the flat plate moves from the vertical to downward facing locations. A new semi-empirical correlation is developed from the measured heat transfer coefficients and interfacial velocities. The correlation shows good agreement with the previous water test results on vertical plates. In the case of the previous other fluid experimental results on the vertical plates, the correlation overpredicts the film boiling heat transfer coefficients at the experimental condition.

Some Effects of Geometry, Orientation, and Acceleration on Pool Film Boiling of Organic Fluids

1966 ◽  
Vol 88 (1) ◽  
pp. 17-23 ◽  
Author(s):  
C. A. Heath ◽  
C. P. Costello
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Atmospheric Pressure ◽  
Boiling Heat Transfer ◽  
Film Boiling ◽  
Transfer Coefficients ◽  
Actual System ◽  
Heat Transfer Coefficients ◽  
Organic Fluids ◽  
The Heat Transfer Coefficient

Ethanol, pentane, and Freon-113 were tested for atmospheric pressure, saturated film-boiling characteristics. Turbulent waves arise close to the bottom of vertical platinum plates and the data become identical to those obtained with horizontal plates, verifying an earlier contention by Y. P. Chang. The equation of Berenson fits the data for both horizontal and vertical heaters fairly well if modified for geometry, and the equation also correctly predicts the effect of acceleration on film-boiling heat-transfer coefficients. At high temperature differences, Berenson’s equation for the heat-transfer coefficient is slightly conservative, which is qualitatively predictable by analyzing the departures of the actual system from the idealized model of Berenson.

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