• Advances in concrete construction
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• v.13 no.5
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• pp.361-365
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• 2022

The objective of this study is to simulate the two-phase flow in pipes with various two-fluid models and determinate the shear stress. A hyperbolic shear deformation theory is used for modelling of the pipe. Two-fluid models are solved by using the conservative shock capturing method. Energy relations are used for deriving the motion equations. When the initial conditions of problem satisfied the Kelvin Helmholtz instability conditions, the free-pressure two-fluid model could accurately predict discontinuities in the solution field. A numerical solution is applied for computing the shear stress. The two-pressure two-fluid model produces more numerical diffusion compared to the free-pressure two-fluid and single-pressure two-fluid models. Results show that with increasing the two-phase percent, the shear stress is reduced.

• Journal of Mechanical Science and Technology
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• v.17 no.11
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• pp.1739-1745
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• 2003

The boiling heat transfer characteristics of two-phase closed thermosyphons with internal grooves are studied experimentally and a simple mathematical model is developed to predict the performance of such thermosyphons. The study focuses on the boiling heat transfer characteristics of a two-phase closed thermosyphons with copper tubes having 50, 60, 70, 80, 90 internal grooves. A two-phase closed thermosyphon with plain copper tube having the same inner and outer diameter as those of grooved tube is also tested for comparison. Methanol is used as working fluid. The effects of the number of grooves, the operating temperature, the heat flux are investigated experimentally. From these experimental results, a simple mathematical model is developed. In the present model, boiling of liquid pool in the evaporator is considered for the heat transfer mechanism of the thermosyphon. And also the effects of the number of grooves, the operating temperature, the heat flux are brought into consideration. A good agreement between the boiling heat transfer coefficient of the thermosyphon estimated from experimental results and the predictions from the present mathematical model is obtained. The experimental results show that the number of grooves and the amount of the working fluid are very important factors for the operation of thermosyphons. The two-phase closed thermosyphon with copper tubes having 60 internal grooves shows the best boiling heat transfer performance.

• Journal of the Korean Society of Propulsion Engineers
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• v.7 no.1
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• pp.57-65
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• 2003

As a compressed water is rapidly expanded through a nozzle, two-phase flow of vapor and liquid is formed in the nozzle due to the flash evaporation. In the present study, critical flow of two-phase fluids is analysized using an Isentropic-Homogeneous-Equilibrium model and a Leung model. Calculation results show that the choke of the two-phase flow can be two different types of continuous and discontinuous chokings. For the stagnation pressure below 10 Mpa it is found that the continuous choking, which is similar to the choking phenomenon of single-phase gas flow, is possible only when the degree of subcooling is less than 10K.

• 한국전산유체공학회:학술대회논문집
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• 2007.10a
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• pp.243-248
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• 2007

A three-dimensional (3D) unstructured hydrodynamic solver for transient two-phase flows has been developed. A two-fluid three-field model was adopted for the two-phase flows. The three fields represent a continuous liquid, an entrained liquid, and a vapour field. The hydrodynamic solver is for the 3D component of a nuclear system code and the component-scale analysis tools for transient two-phase flows. The finite volume method and unstructured grid are adopted, which are useful for the flows in a complicated geometry. The semi-implicit ICE (Implicit Continuous-fluid Eulerian) numerical scheme has been adapted to the unstructured non-staggered grid. This paper presents the numerical method and the preliminary results of the calculations. The results show that the numerical scheme is robust and predicts the phase change and the flow transitions due to boiling and flashing problems well.

• Journal of Integrative Natural Science
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• v.17 no.2
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• pp.43-51
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• 2024

Jung et al.(2015) suggest the two-phase warranty model, which is a general type of warranty model. Under the two-phase warranty, the warranty period is divided into two intervals, one of which is for renewing replacement warranty, and the other is for minimal repair warranty. And warranty policies play a very important role in product marketing. In this paper, we suggest the optimal warranty policy for free extended two-phase warranty. To determine the optimal warranty period, we adopt the expected profit per unit product. So, the expressions for the total expected cost, the sale price and the expected profit per unit product from the manufacturer's point of view are derived. Also, we discuss the optimal warranty period and the numerical examples are provided to illustrate the proposed the warranty policy.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.11a
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• pp.301-306
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• 1996

To predict the average liquid level under the condition of the countercurrent stratified two-phase flow in a pipe, an analytical model has been suggested. This is made by introducing the interfacial level gradient into the liquid-phase and the gas-phase momentum equations. The analytical method for the gas-phase pressure drop calculation with f$_i$ $\neq$ f$_G$ has also been described using the liquid level prediction model developed in the present study.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.7
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• pp.2931-2938
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• 2011

Effective thermal conductivity of three-phase composites, consisting of matrix and two kinds of spherical inclusions, has been derived as an explicit form by extending modified Eshelby model (MEM) for two-phase composites. The present results are compared with those by differential effective medium model (DEMM), which are also compared with the experimental results of two- and three-phase composites in the literatures to be validated. For two-phase composites, the results by MEM are better than those by DEMM for the inclusion volume fraction smaller than 0.5. Comparisons between the results by two models and experimental results have been made for three-phase composite, resulting in that MEM predicts better than DEMM for smaller volume fraction of the inclusion having larger inclusion-to-matrix thermal conductivity ratio, but DEMM predicts better as its volume fraction increases. It has been observed through parametric study that its volume fraction is the critical factor affecting the deviation of predictions by the two models. The results by them show a good agreement with the three-phase composite proposed by Molina et al..

• 한국연소학회:학술대회논문집
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• 2006.10a
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• pp.202-208
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• 2006

The purpose of this research is to model numerically the turbulent gas-particle flows in a rectangular chamber using Eulerian-Eulerian Method. A computer code using the ${\kappa}-{\varepsilon}-Ap$ two-phase turbulence model is developed for the numerical study. This code and the Eulerian multiphase model in FLUENT were used for the numerical simulations of the two-phase flow in a rectangular chamber. The numerical results calculated by the two different turbulent gas-particle codes have shown that the ${\kappa}-{\varepsilon}-Ap$ model results in a stronger diffusion of the flow momentum in the gas-particle turbulence interaction than the Eulerian multiphase model in FLUENT.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.05a
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• pp.124-128
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• 2001

Two-dimensional solidification analysis during rheology forming process of semi-solid aluminum ahoy has been studied Two-phase fluid flow model to investigate the velocity field and temperature distribution is proposed. The unposed mathematical model is applied to the die shape of the two type. To calculate the velocities and temperature fields during rheology forming process, the each governing equation correspondent to the liquid and solid region are adapted. Theoretical model on the basis of the two-phase flow model is the mixture rule of solid and liquid phases. This approach is based on the liquid and solid viscosity.

• Structural Engineering and Mechanics
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• v.57 no.2
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• pp.201-220
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• 2016

A general model of equations of the two-temperature theory of generalized thermoelasticity is applied to study the wave propagation in a fiber-reinforced magneto-thermoelastic medium in the context of the three-phase-lag model and Green-Naghdi theory without energy dissipation. The material is a homogeneous isotropic elastic half-space. The exact expression of the displacement components, force stresses, thermodynamic temperature and conductive temperature is obtained by using normal mode analysis. The variations of the considered variables with the horizontal distance are illustrated graphically. Comparisons are made with the results of the two theories in the absence and presence of a magnetic field as well as a two-temperature parameter. A comparison is also made between the results of the two theories in the absence and presence of reinforcement.