Jet Impingement Boiling From a Circular Free-Surface Jet During Quenching: Part 2—Two-Phase Jet

2001 ◽  
Vol 123 (5) ◽  
pp. 911-917 ◽  
Author(s):  
David E. Hall ◽  
Frank P. Incropera ◽  
Raymond Viskanta
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Single Phase ◽  
Jet Impingement ◽  
Film Boiling ◽  
Two Phase ◽  
Maximum Heat ◽  
Maximum Heat Flux ◽  
Jet Impingement Boiling ◽  
Surface Jet

A proposed technique for controlling jet impingement boiling heat transfer involves injection of gas into the liquid jet. This paper reports results from an experimental study of boiling heat transfer during quenching of a cylindrical copper specimen, initially at a uniform temperature exceeding the temperature corresponding to maximum heat flux, by a two-phase (water-air), circular, free-surface jet. The second phase is introduced as small bubbles into the jet upstream of the nozzle exit. Data are presented for single-phase convective heat transfer at the stagnation point, as well as in the form of boiling curves, maximum heat fluxes, and minimum film boiling temperatures at locations extending from the stagnation point to a radius of ten nozzle diameters. For void fractions ranging from 0.0 to 0.4 and liquid-only velocities between 2.0 and 4.0 m/s 11,300⩽Red,fo⩽22,600, several significant effects are associated with introduction of the gas bubbles into the jet. As well as enhancing single-phase convective heat transfer by up to a factor of 2.1 in the stagnation region, addition of the bubbles increases the wall superheat in nucleate boiling and eliminates the temperature excursion associated with cessation of boiling. The maximum heat flux is unaffected by changes in the void fraction, while minimum film boiling temperatures increase and film boiling heat transfer decreases with increasing void fraction. A companion paper (Hall et al., 2001) details corresponding results from the single-phase jet.

Jet Impingement Boiling From a Circular Free-Surface Jet During Quenching: Part 1—Single-Phase Jet

2001 ◽  
Vol 123 (5) ◽  
pp. 901-910 ◽  
Author(s):  
David E. Hall ◽  
Frank P. Incropera ◽  
Raymond Viskanta
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Free Surface ◽  
Boiling Heat Transfer ◽  
Single Phase ◽  
Jet Impingement ◽  
Nucleate Boiling ◽  
Transient Temperature ◽  
Spatial Distributions ◽  
Maximum Heat

This paper reports results from an experimental study of boiling heat transfer during quenching of a cylindrical copper disk by a subcooled, circular, free-surface water jet. The disk was heated to approximately 650°C, and as quenching occurred, transient temperature measurements were taken at discrete locations near the surface and applied as boundary conditions in a conduction model to deduce transient heat flux distributions at the surface. Results are presented in the form of heat flux distributions and boiling curves for radial locations varying from the stagnation point to ten nozzle diameters for jet velocities between 2.0 and 4.0 m/s 11,300⩽Red⩽22,600. Data for nucleate boiling in the stagnation region and spatial distributions of maximum heat flux are presented and are in good agreement with correlations developed from steady-state experiments. Spatial distributions of minimum film boiling temperatures and heat fluxes are also reported and reveal a fundamental dependence on jet deflection and streamwise location. A companion paper (Hall et al., 2001) describes single-phase and boiling heat transfer measurements from a two-phase (water-air), free-surface, circular jet produced by injecting air bubbles into the jet upstream of the nozzle exit.

scholarly journals ELETRIC FIELD ENHANCEMENT AND DETERIORATION OF BOILING HEAT TRANSFER AND CRITICAL HEAT FLUX IN DIELECTRIC FLUIDS

2001 ◽  
Vol 1 (1) ◽  
pp. 32
Author(s):  
P. M. Carrica ◽  
V. Masson
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Electric Fields ◽  
Boiling Heat Transfer ◽  
Nucleate Boiling ◽  
Film Boiling ◽  
Two Phase ◽  
Boiling Regime ◽  
Dielectric Fluids

We present the results of an experimental study of the effects of externally imposed electric fields on boiling heat transfer and critical heat flux (CHF) in dielectric fluids. The study comprises the analysis of geometries that, under the effects of electric fields, cause the bubbles either to be pushed toward the heater or away from it. A local phase detection probe was used to measure the void fraction and the interfacial impact rate near the heater. It was found that the critical heat flux can be either augmented or reduced with the application of an electric field, depending on the direction of . In addition, the heat transfer can be slightly enhanced or degraded depending on the heat flux. The study of the two-phase flow in nucleate boiling, only for the case of favorable dielectrophoretic forces, reveals that the application of an electric field reduces the bubble detection time and increases the detachment frequency. It also shows that the two-phase flow characteristics of the second film boiling regime resemble more a nucleate boiling regime than a film boiling regime.

Numerical Investigation on Pool Boiling Over a Vertical Tube Coupled With In-Tube Condensation

2019 ◽  
Author(s):  
Shuai Ren ◽  
Wenzhong Zhou
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Boiling Heat Transfer ◽  
Power Plants ◽  
Pool Boiling ◽  
Heat Removal ◽  
Vertical Tube ◽  
Two Phase ◽  
Maximum Heat ◽  
Maximum Heat Transfer

Abstract Pool boiling and in-tube condensation phenomena have been investigated intensively during the past decades, due to the superior heat transfer capacity of the phase change process. In passive heat removal heat exchangers of nuclear power plants, the two phase-change phenomena usually occur simultaneously on both sides of the tube wall to achieve the maximum heat transfer efficiency. However, the studies on the effects of in-tube condensation on external pool boiling heat transfer are very limited, especially in numerical computation aspect. In the present study, the saturated pooling boiling over a vertical tube under the influences of in-tube steam condensation is investigated numerically. The Volume of Fluid (VOF) interface tracking method is employed based on the 2D axisymmetric Euler-Euler multiphase frame. The phase change model combining with a mathematical smoothing algorithm and a temporal relaxation procedure has been implemented into CFD platform by user defined functions (UDFs). The two-phase flow pattern and bubble behavior have been analyzed. The effects of inlet steam mass flow rate on boiling heat transfer are discussed.

Analysis of Film Boiling on Vertical Surfaces

1962 ◽  
Vol 84 (1) ◽  
pp. 55-62 ◽  
Author(s):  
J. C. Y. Koh
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Flow Problem ◽  
Interfacial Shear ◽  
Film Condensation ◽  
Film Boiling ◽  
Two Phase ◽  
Boundary Layer Equations ◽  
Liquid Phases ◽  
Vertical Flat Plate

The two phase flow problem in laminar film boiling on a vertical flat plate is analyzed. The shear stress and vapor velocity at the vapor-liquid interface are taken into account. The problem is treated by solving simultaneously the boundary-layer equations for the vapor and liquid phases. In contrast to the film-condensation problem where the heat transfer is independent of the ρμ ratio, and where the interfacial shear can be neglected for a Prandtl number of unity or larger, it is shown that the ρμ ratio is an important parameter in the film-boiling heat transfer, and that the interfacial shear is quite different from zero.

Boiling Heat Transfer Characteristics of Staggered-array Water Impinging Jets on Hot Steel Plate

2018 ◽  
Vol 140 (3) ◽  
Author(s):  
Sang Gun Lee ◽  
Jin Sub Kim ◽  
Dong Hwan Shin ◽  
Jungho Lee
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Surface Temperature ◽  
Boiling Heat Transfer ◽  
Steel Plate ◽  
Nucleate Boiling ◽  
Impinging Jets ◽  
Heat Transfer Characteristics ◽  
Maximum Heat ◽  
Maximum Heat Flux

The effect of staggered-array water impinging jets on boiling heat transfer was investigated by a simultaneous measurement between boiling visualization and heat transfer characteristics. The boiling phenomena of staggered-array impinging jets on hot steel plate were visualized by 4K UHD video camera. The surface temperature and heat flux on hot steel plate was determined by solving 2-D inverse heat conduction problem, which was measured by the flat-plate heat flux gauge. The experiment was made at jet Reynolds number of Re = 5,000 and the jet-to-jet distance of staggered-array jets of S/Dn = 10. Complex flow interaction of staggered-array impinging jets exhibited hexagonal flow pattern like as honey-comb. The calculated surface heat transfer profiles show a good agreement with the corresponding boiling visualization. The peak of heat flux accords with the location which nucleate boiling is occurred at. In early stage, the positions of maximum heat flux locate at the stagnation point of each jet as the relatively low surface temperature is shown at their positions. At the elapsed time of 10 s, the flat shape of heat flux profile is formed in the hexagonal area where the interacting flow uniformly cools down the wetted surface. After that, the wetted area continuously enlarges with time and the maximum heat flux is observed at its peripheral. These results point out that the flow interaction of staggered-array jets effectively cools down the closer area around jets and also show an expansion of nucleate boiling and suppression of film boiling during water jet cooling on hot steel plate. [This work was supported by the KETEP grant funded by the Ministry of Trade, Industry & Energy, Korea (Grant No. 20142010102910).]

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