On the Prediction of the Minimum Pool Boiling Heat Flux

1980 ◽  
Vol 102 (3) ◽  
pp. 457-460 ◽  
Author(s):  
J. H. Lienhard ◽  
V. K. Dhir
Keyword(s):  
Heat Flux ◽  
Film Boiling ◽  
Vapor Film ◽  
Saturated Liquid ◽  
Flat Plates ◽  
Rate Of Increase ◽  
Constant Rate ◽  
Empirical Generalizations ◽  
Film Collapse ◽  
Minimum Heat

A criterion is offered for the collapse of film boiling in a saturated liquid at the minimum heat flux. The criterion says the vapor film collapse occurs when insufficient vapor is generated to sustain the growing wave after it reaches a constant rate of increase of amplitude. This criterion yields an accurate prediction for horizontal flat plates and cylinders. The prediction requires the use of empirical generalizations about the configuration of film boiling, which are also developed here.

Free Convection Film Boiling Heat Transfer From a Rotating Surface

1992 ◽  
Vol 114 (3) ◽  
pp. 695-702 ◽  
Author(s):  
J. Orozco ◽  
H. Francisco
Keyword(s):  
Free Convection ◽  
Surface Flux ◽  
Film Boiling ◽  
Integral Approach ◽  
Vapor Film ◽  
Experimental Facility ◽  
Layer Model ◽  
Rotating Surface ◽  
Minimum Heat ◽  
Good Agreement

A boundary layer model of laminar, subcooled, free convection film boiling from a rotating sphere has been developed. The conservation equations for the vapor and liquid were simplified, transformed into ordinary differential equations using an integral approach, and solved numerically. The theoretical variation of vapor film thickness with heater temperature and the resulting boiling fluxes were investigated. An experimental facility was built for the purpose of verifying the validity of the theoretical model and good agreement was found between the model and the experimental data at low rpm. The instability of the vapor film near the minimum heat flux for a rotating surface flux was also investigated.

Effect of Hydrated Salt Additives on Film Boiling Behavior at Vapor Film Collapse

2008 ◽  
Author(s):  
Takahiro Arai ◽  
Masahiro Furuya
Keyword(s):  
High Speed ◽  
Video Camera ◽  
Film Boiling ◽  
Vapor Film ◽  
Quenching Temperature ◽  
Steel Sphere ◽  
Digital Video Camera ◽  
Collapse Temperature ◽  
Test Film ◽  
Film Collapse

A high-temperature stainless-steel sphere was immersed into various salt solutions to test film boiling behavior at vapor film collapse. The film boiling behavior around the sphere was observed with a high-speed digital-video camera. Because salt additives enhanced condensation heat transfer, the observed vapor film was thinner. Surface temperature of the sphere was measured. Salt additives increased the quenching (vapor film collapse) temperature, because frequency of direct contact between sphere surface and coolant increased. Quenching temperature rises with increased salt concentration. The quenching temperature, however, approaches a constant value when the slat concentration is close to its saturation concentration. The quenching temperature is well correlated with ion molar concentration, which is a number density of ions, regardless of the type of hydrated salts.

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.

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