scholarly journals Transient evolution of the heat transfer and the vapor film thickness at the drop impact in the regime of film boiling

2018 ◽  
Vol 30 (12) ◽  
pp. 122109 ◽  
Author(s):  
G. Castanet ◽  
W. Chaze ◽  
O. Caballina ◽  
R. Collignon ◽  
F. Lemoine
Keyword(s):  
Heat Transfer ◽  
Film Thickness ◽  
Drop Impact ◽  
Film Boiling ◽  
Vapor Film

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.

Heat Transfer During Drop Impact Onto Wetted Heated Smooth and Structured Substrates: Experimental and Theoretical Study

2010 ◽  
Author(s):  
Tatiana Gambaryan-Roisman ◽  
Mete Budakli ◽  
Ilia V. Roisman ◽  
Peter Stephan
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Film Thickness ◽  
Spray Cooling ◽  
Drop Impact ◽  
Interface Temperature ◽  
Heated Plate ◽  
Initial Film ◽  
Impact Parameters ◽  
Heated Plates

Spray cooling is a very effective means of heat removal from hot surfaces. Its efficiency can be further improved using structured wall surfaces. One of the fundamental processes governing spray cooling is an impact of a single cold droplet onto a heated wetted wall. The hydrodynamics of drop impact governs the transient heat transport in the film and in the wall. We study hydrodynamics and heat transfer during impact of a single drop onto heated smooth and structured heated plates. The temperature distribution in the heated plates has been measured with seven thermocouples. The splash dynamics and the evolution of interface temperature distribution have been visualized using high-speed infrared thermography. The film thickness evolution in the inner region has been measured using chromatic confocal imaging technique. Initial film thickness and drop impact parameters have been varied in the experiments. The evolution of the temperature distribution at the liquid-gas interface and the instationary temperature distribution in the heated plate depend on the initial film thickness, impact parameters and the plate topography. A self-similar analytical solution of the full Navier-Stokes equations and of the energy equation is obtained for the velocity and temperature fields in the spreading film. The theory allows prediction of the contact temperature and the residual film thickness.

Flow Film Boiling From a Sphere to Subcooled Freon-11

1986 ◽  
Vol 108 (4) ◽  
pp. 934-938 ◽  
Author(s):  
J. A. Orozco ◽  
L. C. Witte
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Liquid Velocity ◽  
Flow Boiling ◽  
Empirical Correlation ◽  
The Other ◽  
Film Boiling ◽  
Vapor Film ◽  
Peak Heat Flux ◽  
Semi Empirical

The boiling curves for flow boiling of freon-11 from a fluid-heated 3.81-cm-dia copper sphere showed dual maxima. One maximum corresponded to the nucleate peak heat flux while the other was caused by transitory behavior of the wake behind the sphere. Film boiling data were predicted well by the theory of Witte and Orozco. A semi-empirical correlation of the film boiling data accounting for both liquid velocity and subcooling predicted the heat transfer to within +/− 20 percent. The conditions at which the vapor film became unstable were also determined for various sub-coolings and velocities.

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