• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.22 no.5
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• pp.289-295
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• 2010

In this study, the enhancement of the thermal conductivity of water in the presence of multi-walled carbon nanotubes, MWCNT, was investigated. Sodium Dodecyl Sulfate, SDS, and Polyvinylpyrrolidone, PVP, were employed as the dispersant. SDS or PVP was added in pure water. And then, MWCNT of 0.0005, 0.001, 0.002, 0.003, 0.004, 0.005, 0.01, and 0.02 vol% was dispersed respectively. The thermal conductivity and the viscosity were measured with a transient hot-wire instrument built for this study and the DV II+ Pro viscometer. The results showed that PVP had good thermal conductivity at 300 wt% and this was better than that of SDS 100 wt%, also, the viscosity of nano fluid added PVP rapidly increased until 0.02 vol%.

• Nuclear Engineering and Technology
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• v.44 no.8
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• pp.831-846
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• 2012

KAERI has developed a two-phase CFD code, CUPID, for a refined calculation of transient two-phase flows related to nuclear reactor thermal hydraulics, and its numerical models have been verified in previous studies. In this paper, the CUPID code is validated against experiments on the downcomer boiling and moderator flow in a Calandria vessel. Physical models relevant to the validation are discussed. Thereafter, multi-scale thermal hydraulic analyses using the CUPID code are introduced. At first, a component-scale calculation for the passive condensate cooling tank (PCCT) of the PASCAL experiment is linked to the CFD-scale calculation for local boiling heat transfer outside the heat exchanger tube. Next, the Rossendorf coolant mixing (ROCOM) test is analyzed by using the CUPID code, which is implicitly coupled with a system-scale code, MARS.

• Nuclear Engineering and Technology
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• v.44 no.1
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• pp.33-42
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• 2012

In the present study, CFD is employed to investigate phenomena occurring during a process of thermal stratification in U-bent pipes at transitional Reynolds number. URANS evaluation had been chosen for its low computational costs during transient analysis and for the evaluation of modeling performance in these conditions. Application of CFD at transitional Reynolds number and buoyancy driven flows indeed contains deeper uncertainties in relation to the range of applicability for hydrodynamic and thermal models. The methodology applied in the work points out, through validations with the basic problems constituting the complex stratified phenomenon, the applicability of the current turbulence modeling. Accurate predictions have been found in relation to transitional Reynolds number in bent pipes and region of stability induced by the gravitational field. On the other hand the defects introduced in the unstable region of the U bent pipe, are discussed in relation to the adopted modeling.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2012.05a
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• pp.255-256
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• 2012

In this study, strain properties of high strength concrete using light weight aggregate which is widely used in recent years are evaluated. For these purpose, thermal strain, transient creep were measured in prestressed condition as 0, 20, 40% of specimen strength at target temperature with 60MPa specimens which was using normal and light weight aggregate. As a result, light weight aggregate is more advantageous for the control of strain than normal aggregate because of its low thermal expansion.

• Proceedings of the KWS Conference
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• 2005.11a
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• pp.126-128
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• 2005

This paper presents a 3-D finite element analysis of a magneto-thermal coupled problem with moving conductor. In the magnetic and thermal analyses, temperature-dependent magnetic and thermal material properties were considered. Transient finite element method for analysis of moving conductor needs many number of elements and much time to make calculation. Therefore, in this paper, finite element formulation derived from quasi-state is adopted. Finite element results were compared with the experimental results. The results demonstrate that this approach is suitable to solve the magneto-thermal coupled problem.

• Journal of Hydrogen and New Energy
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• v.12 no.2
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• pp.147-155
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• 2001

To measure of thermal loading in the combustion chamber of hydrogen engine with dual injection, instantaneous wall-surface temperature and unsteady heat flux of the cylinder head are measured and analyzed. The maximum wall surface temperature is shown in direct injection region which has large heat supplied. Partial and spatial temperatures have slight deviation in transient region of injection, though injection method change suddenly. All of thermal characteristics such as instantaneous temperature, temperature swing and heat flux of hydrogen engine with dual injection are remarkably higher than those of gasoline engine. It means necessity of additional countermeasure of thermal loading.

• Nuclear Engineering and Technology
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• v.32 no.2
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• pp.99-107
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• 2000

A probabilistic integrity analysis method is presented for a reactor vessel under pressurized thermal shock(PTS) based on Monte Carlo simulation. This method can be applied to the structural integrity assessment of a reactor vessel subjected to pressurized thermal shock where the coolant temperature transient cannot be expressed explicitly as a time function. An axially or circumferentially oriented infinite length surface crack is assumed to be in the beltline weld region of the rector vessel's inside surface. The random variables are the initial crack depth, neutron fluence on the vessel's inside surface, the copper and nickel content of the vessel materials, R $T_{NDT}$ , $K_{IC}$ , and K/aub la/. The reliability of a sample reactor vessel under PTS is assessed quantitatively and the influence of the amount of neutron fluence is also examined by applying the present method.sent method.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.1 s.232
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• pp.27-34
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• 2005

We analyze in detail axially symmetric theoretical study for the photothermal pulsed radiometry of a cylindrical model. The theoretical solutions describe the transient infrared radiation from the sample heated by short-duration pulsed heating. In the conventional transmission radiometry technique, the excitation source and the detector are on opposite sides of the sample, otherwise in the new single ended radiometry technique, the excitation source and the detector are on same sides of the sample. The analytical solution described for photothermal radiometry in this study would not need to cut or polish samples to measure the thermal diffusivity. Therefore the radial area and axial thickness of samples are not limited. The effects of excitation pulse duration and the area of heat source are discussed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.5
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• pp.617-623
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• 2004

This paper describes a dynamic thermal model for a representative dual axis rotational Chemical-Mechanical Polishing (CMP) tool. The model is one-dimensional but configured in the two-dimensional space and consists of three sub-models (pad, wafer and slurry fluid), with the first and the second that are time-dependent heat conduction-convection models with linear stationary (wafer) and nonlinear moving (pad) boundary conditions, and the last one that is a heat transport-convection model (slurry fluid). The modeling approach is validated by comparing the simulation results with available experimental data.

• Bulletin of the Society of Naval Architects of Korea
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• v.12 no.1
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• pp.9-22
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• 1975

As a second step of a thermal stress analysis in a watertight bulkhead plate during welding of a spool type penetration piece, is idealized as a thin circular disk with a clamped boundary. The exact solution for the transient temperature distribution and associated quasi-static thermal stresses which arise in a circular disk subjected to an instantaneous point source of heat acting in its interior has been obtained. And the solutions have been extended to the case of moving source of heat with the aid of the Duhamel's superposition integral and the results finally derived have been compared with the other results from the typical cases. The solutions can be applied to the problem such as a welding of a penetration piece on the watertight bulkhead and also applicable to the problems which occur in cutting or welding.