• Nuclear Engineering and Technology
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• v.32 no.1
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• pp.34-45
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• 2000

This study is concerned with the experimental test and numerical analysis of the heat transfer and solidification of the molten metal pool with overlying coolant with boiling. In the test, the metal pool is heated from the bottom surface and coolant is injected onto the molten metal pool. Experiments were performed by changing the test section bottom surface temperature of the metal layer and the coolant injection rate. The two-phase boiling coolant experimental results are compared against the dry test data without coolant or solidification of the molten metal pool, and against the crust formation experiment with subcooled coolant. Also, a numerical analysis is performed to check on the measured data. The numerical program is developed using the enthalpy method, the finite volume method and the SIMPLER algorithm. The experimental results of the heat transfer show general agreement with the calculated values. The present empirical test and numerical results of the heat transfer on the molten metal pool are apparently higher than those without coolant boiling. This is probably because this experiment was performed in concurrence of solidification in the molten metal pool and the rapid boiling of the coolant. The other experiments were performed without coolant boiling and the correlation was developed for the pure molten metal without phase change.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.20 no.1
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• pp.33-41
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• 2022

Liquid Bi pool is a candidate electrode for an electrometallurgical process in the molten LiCl-KCl eutectic to treat the spent nuclear fuels from nuclear power plants. The electrochemical behavior of Bi³⁺ ions and the electrode reaction on liquid Bi pool were investigated with the cyclic voltammetry in an environment with or without BiCl₃ in the molten LiCl-KCl eutectic. Experimental results showed that two redox reactions of Bi³⁺ on inert W electrode and the shift of cathodic peak potentials of Li⁺ and Bi³⁺ on liquid Bi pool electrode in molten LiCl-KCl eutectic. It is confirmed that the redox reaction of lithium with respect to the liquid Bi pool electrode would occur in a wide range of potentials in molten LiCl-KCl eutectic. The obtained data will be used to design the electrometallurgical process for treating actinide and lanthanide from the spent nuclear fuels and to understand the electrochemical reactions of actinide and lanthanide at liquid Bi pool electrode in the molten LiCl-KCl eutectic.

• Proceedings of the Korean Nuclear Society Conference
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• 1997.10a
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• pp.719-725
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• 1997

This paper presents results of experimental studies on the heat transfer and solidification of the molten metal pool with overlying coolant with boiling. The metal pool is heated from the bottom surface and coolant is injected onto the molten metal pool. As a result, the crust, which is a solidified layer, may form at the top of the molten metal pool. Heat transfer is accomplished by a conjugate mechanism, which consists of the natural convection of the molten metal pool, the conduction in the crust layer and the convective boiling heat transfer in the coolant. This work examines the crust formation and the heat transfer rate on the molten metal pool with boiling coolant. The simulant molten pool material is tin (Sn) with the melting temperature of 232$^{\circ}C$. Demineralized water is used as the working coolant. The crust layer thickness was ostensibly varied by the heated bottom surface temperature of the test section, but not much affected by the coolant injection rate. The correlation beかeon the Nusselt number and the Rayleigh number in the molten metal Pool region of this study is compared against the crust formation experiment without coolant boiling and the literature correlations. The present experimental results are higher than those from the experiment without coolant boiling, but show general agreement with the Eckert correlation, with some deviations in the high and low ends of the Rayleigh number. This discrepancy is currently attributed to concurrent rapid boiling of the coolant on top of the metal layer.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.2
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• pp.226-233
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• 1999

An experimental study has been performed on natural convection heat transfer with a rapid crust formation in the molten metal pool of a low Prandtl number fluid. Two types of steady state tests, a low and high geometric aspect ratio cases in the molten metal pool, were performed. The crust thickness by solidification was measured 88 a function of boundary surface temperatures. The experimental results on the relationship between the Nusselt number and Rayleigh number In the molten metal pool with a crust formation were compared with existing correlations. The experimental study has shown that the bottom surface temperature of the molten metal layer, in all experiments. is the major influential parameter in the crust formation, duo to the natural convection flow. The Nusselt number of the case without a crust formation in the molten metal pool is greater than that of the case with the crust formation at the same Rayleigh number. The present experimental results on the relationship between the Nusselt number and Rayleigh number In the molten metal pool match well with Globe and Dropkin's correlation. From the experimental results, a now correlation between the Nusslet number and Rayleigh number in the molten metal pool with the crust formation was developed as $Nu=0.0923(Ra)^{0.302}$ ($2{\times}10^4< Ra<2{\times}10^7$).

• Proceedings of the Korean Nuclear Society Conference
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• 1998.05a
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• pp.812-817
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• 1998

Experimental studies on heat transfer and solidification of the molten metal pool with overlying coolant with boiling were performed The simulant molten pool material is tin (Sn) with the melting temperature of 232$^{\circ}C$. Demineralized water and R113 are used as the working coolant. This work examines the crust formation and the heat transfer characteristics of the molten metal pool immersed in the boiling coolant. The Nusselt number and the Rayleigh number in the molten metal Pool region of this study are compared between the water coolant case and the R113 coolant case. The experimental results or the water coolant are higher than those for R113. Also, the empirical relationship of the Nusselt number and the Rayleigh number is compared with the literature correlations measure from mercury. The present experimental results are higher than the literature correlations. It is believed that this discrepancy is caused by the effect of heat loss to the environment on the natural convection heat transfer in the molten pool.

• Journal of Welding and Joining
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• v.11 no.2
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• pp.62-73
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• 1993

Weld pool oscillation for the full-penetration GTA welding process was investigated for its possible application to weld penetration control through theoretical modeling and experiment. Energy method was used to estimate the natural frequency of the molten pool having the physically-acceptable weld geometry and oscillation modes. An unique experimental system was built which had the data acquisiton and video capabilities so that the pool oscillation signals and molten pool surfaces could be monitored continuously. Pool oscillation was detected through arc voltage and arc light emission simultaneously. The signal from arc light emission showed good coherence with that from arc voltage, and arc light generated the higher quality signal. The molten pool was found to oscillate in different oscillation modes based on the travel speed and weld geometry. The natural frequency estimated from the theoretical model agreed reasonably well with the experimental results.

• Proceedings of the KWS Conference
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• 2010.05a
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• pp.53-53
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• 2010

The purpose of this paper is to propose a mathematical model of welding current for the P-GMAW by modifying the well known GMAW model. Welding power circuit is simply modeled as a RL electric circuit and solved as an ODE equation. The welding current depends on the joint shape, molten pool and welding parameters. To compare the molten pool effect to the welding current, CFD numerical simulation technique was adopted. Welding experiment is also conducted with the same welding parameters as used in numerical simulations to verify the proposed welding current model. The current model which is considered molten pool shape, is more fit to experiment result.

• Journal of Welding and Joining
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• v.28 no.4
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• pp.55-60
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• 2010

The purpose of this paper is to propose a mathematical model of welding current for the P-GMAW by modifying the well known GMAW model. Welding power circuit is simply modeled as a RL electric circuit and solved as an ODE equation. The welding current depends on the joint shape, molten pool and welding parameters. To compare the molten pool effect to the welding current, CFD numerical simulation technique was adopted. Welding experiment is also conducted with the same welding parameters as used in numerical simulations to verify the proposed welding current model. The current model which is considered molten pool shape, is more fit to experiment result.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1996.11a
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• pp.27-41
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• 1996

In this study the heat transfer and fluid flow of the molten pool in stationary gas tungsten arc welding using argon shielding gas were investigated. Transporting phenomena from the welding arc to the base material surface, such as current density, heat flux, arc pressure and shear stress acting on the weld pool surface, were taken from the simulation results of the corresponding welding arc. Various driving forces for the weld pool convection were considered, self-induced electromagnetic, surface tension, buoyancy, and impinging plasma arc forces. Furthermore, the effect of surface depression due to the arc pressure acting on the molten pool surface was considered. Because fusion boundary has a curved and unknown shape during welding, a boundary-fitted coordinate system was adopted to precisely describe the boundary for the momentum equation. The numerical model was applied to AISI 304 stainless steel and compared with the experimental results.

• Journal of Mechanical Science and Technology
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• v.18 no.6
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• pp.990-1001
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• 2004

The retention of a molten pool vessel cooled by internal vessel reflooding and/or external vessel reactor cavity flooding has been considered as one of severe accident management strategies. The present numerical study investigates the effect of both internal and external vessel mixed cooling on an internally heated molten pool. The molten pool is confined in a hemispherical vessel with reference to the thermal behavior of the vessel wall. In this study, our numerical model used a scaled-down reactor vessel of a KSNP (Korea Standard Nuclear Power) reactor design of 1000 MWe (a Pressurized Water Reactor with a large and dry containment). Well-known temperature-dependent boiling heat transfer curves are applied to the internal and external vessel cooling boundaries. Radiative heat transfer has been considered in the case of dry internal vessel boundary condition. Computational results show that the external cooling vessel boundary conditions have better effectiveness than internal vessel cooling in the retention of the melt pool vessel failure.