Shell Thinning Phenomena Affected by Heat Transfer, Nozzle Design and Flux Chemistry in Billets Moulds

One of the methods used for industrial cleansing applications employs a mixture of gaseous nitrogen and liquid water injected upstream of a converging-diverging nozzle located at the end of a straight wand assembly. The idea is to get the mixture to impact the surface at the maximum momentum flux possible in order to maximize the cleansing effectiveness. This paper presents an analysis geared towards this application in which the effects of slip and heat transfer between the gas and liquid phases are present. The model describes the liquid momentum flux (considered a figure of merit for cleansing) under a host of design conditions. While it is recognized that the emulsification mechanism responsible for cleansing is far more complicated than simply being solely dependent on the liquid momentum flux, the analysis presented here should prove useful in providing sufficiently accurate results for nozzle design purposes. [S0098-2202(00)01801-0]

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Fitness for Service Assessment of the Thermal Sleeve Weld Failure for Steam Generator Reheat Condensate Nozzle in CANDU6 Nuclear Plant

ASME 2011 Pressure Vessels and Piping Conference: Volume 3 ◽

10.1115/pvp2011-57615 ◽

2011 ◽

Author(s):

Reza Ghafouri-Azar ◽

Alice Sze ◽

Dan Vlaicu ◽

Mike Stojakovic

Keyword(s):

Heat Transfer ◽

Steam Generator ◽

Structural Integrity ◽

Convection Heat Transfer ◽

Internal Surface ◽

Service Evaluation ◽

Nozzle Design ◽

Thermal Shield ◽

Weld Failure ◽

Service Conditions

An assessment was completed to address the failure of internal thermal sleeve weld for reheat condensate nozzle of steam generators. The plant is operated by Ontario Power Generation (OPG) in Pickering, and has CANDU®6 type reactors. The objective of assessment was to evaluate the effect of the failed weld on the overall structural integrity of the nozzle for the defined operating service conditions. The fitness for service of the steam generator nozzle was demonstrated by comparing the maximum stress ranges of the initial nozzle design with the failed weld nozzle configuration under the same service conditions. Two nozzle configurations were considered for this assessment. One configuration represents the original shape with no leakage at weld indicating as-designed condition. Transient heat transfer and the stress analyses were performed according to the defined service limits. Another configuration completed for the faulty condition in which weld is failed and thermal sleeve separated. The same transients as the first configuration were applied, but the leakage was introduced at the thermal sleeve weld. The effect of leakage was considered by changing the convection heat transfer coefficient in annulus area between the external side of sleeve and internal surface of the nozzle. Critical locations on the nozzle were identified for the whole transient cycles, and assigned different stress lines. The maximum and minimum stress intensity ranges of the initial nozzle design and the cracked weld nozzle design were compared for these stress lines. It was concluded that the thermal sleeve weld failure with the conservatively postulated leakage flow provides better results in terms of stress ranges compared to the as-design condition. The thermal shield was over constrained in as-design condition. And for the fitness for service evaluation in was decided to leave the failed weld in-service without repairing it.

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Numerical Study of Nozzle Design on Cadmium Quenching Process in Thermochemical Splitting of Water

Volume 6: Emerging Technologies: Alternative Energy Systems; Energy Systems: Analysis, Thermodynamics and Sustainability ◽

10.1115/imece2009-12862 ◽

2009 ◽

Author(s):

Jianhu Nie ◽

Yitung Chen ◽

Bunsen Wong ◽

Lloyd C. Brown

Keyword(s):

Heat Transfer ◽

Hydrogen Production ◽

Gas Flow ◽

Numerical Study ◽

Three Dimensional ◽

Maximum Velocity ◽

Numerical Results ◽

Nozzle Design ◽

Flow And Heat Transfer ◽

Quenching Process

Three-dimensional liquid-gas flow with condensation during cadmium quenching process for hydrogen production was numerically simulated in order to effectively guide the design of solar decomposer and vapor quencher. The mixture model was selected for modeling the multiphase flow, and the two-equation RNG k-ε model was used to model the turbulent flow and heat transfer. Numerical results including velocity, temperature, pressure, and mole fraction distributions were obtained for different nozzle designs. Numerical results showed that flow is relatively low in the decomposer and close to the bottom and the top inlets. The maximum velocity develops in the region near the entrance of the quenching nozzle as the nozzle angle is small. As the nozzle angle is large, the maximum velocity appears in the exit tube. Temperature, pressure and cadmium vapor distributions are also directly affected by the nozzle angle.

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Control of Slag-Dragging Effects at the Metal–Slag Interface through Electromagnetic Brake in a Slab Mold

Journal for Manufacturing Science and Production ◽

10.1515/jmsp-2014-0042 ◽

2015 ◽

Vol 15 (1) ◽

pp. 119-130 ◽

Cited By ~ 1

Author(s):

R. D. Morales ◽

S. García-Hernández ◽

I. Calderón-Ramos ◽

María Salazar-Campoy ◽

J. de J. Barreto

Keyword(s):

Capillary Number ◽

Slag Layer ◽

Operating Conditions ◽

Slag Viscosity ◽

Nozzle Design ◽

Interface Instability ◽

Operating Variables ◽

Critical Capillary Number ◽

The Magnetic Field ◽

Flux Chemistry

AbstractTurbulent flow when steel is delivered through a nozzle in a slab mold induces dragging forces at the metal–slag interface that entrain slag droplets into the metal bulk. These dragging effects are discontinuous and correspond to the velocity fluctuations of turbulence at that interface which themselves, are dependent on nozzle immersion, nozzle design, mold width and casting speed. Slag viscosity and density, metal viscosity and slag layer thickness are employed to estimate that critical velocity which is embodied in a critical capillary number for some established mold operating conditions. This approach permits the link between all operating variables including flux chemistry and nozzle design with the interface instability. A relationship between the capillary number and the magnetic field strength used to brake the liquid steel is established which is used to assure the interface stability for any operating condition and flux chemistry.

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