• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.6
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• pp.84-93
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• 2018

Three-dimensional (3D) numerical simulations have been carried out to study how coolant injection conditions influence the cooling efficiency and projectile ejection performance in a mixture-gas ejection system (or gas-steam launch system). The 3D single-phase computational model was verified using a 1D model constructed with reference to the previous research and then a two-phase flow computation simulating coolant injection on to hot gas was performed using a DPM (Discrete Phase Model). As a result of varying the coolant flow rate and number of injection holes, cooling efficiency was improved when the number of injection holes were increased. In addition, the change of the coalescence frequency and spatial distribution of coolant droplets caused by the injection condition variation resulted in a change of the droplet diameter, affecting the evaporation rate of coolant. The evaporation was found to be a critical factor in the design optimization of the ejection system by suppressing the pressure drop while the temperature decreases inside the breech.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.6
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• pp.518-525
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• 2006

The present experiments have been performed for obtaining the melting heat transfer characteristics of micro-encapsulated solid-liquid phase-change material and water mixture slurry flow in a circular tube heated with constant wall heat flux. The phase change material having a low melting point was selected for a domestic cooling system in the present study. The governing parameters were found to be latent heat material concentration, heat flux, and the slurry velocity. The experimental results revealed that the increase of tube wall temperature of latent microcapsule slurry was lower than that of water caused by the heat absorption of fusion.

• Proceedings of the SAREK Conference
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• 2005.11a
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• pp.193-198
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• 2005

The present experiments have been performed for obtaining the melting heat transfer characteristics of micro-encapsulated solid-liquid phase change material and water mixed slurry flow in a circular tube heated with constant wall heat flux. The phase change material having a low melting point was selected for a domestic cooling system in the present study. The governing parameters were found to be latent heat material concentration, heat flux, and the slurry velocity. The experimental results revealed that the increase of tube wall temperature of latent microcapsule slurry was lower than that of water caused by the heat absorption of fusion.

• Proceedings of the KSR Conference
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• 2009.05b
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• pp.507-513
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• 2009

The cooling technology of power conversion semiconductors in the propulsion system for the HEMU(High Electrical Multi Unit) are applied in water cooling method and phase change method such as the immersed type and the heat pipe type. Both of cooling systems need a condenser and a fan through forced wind to emit that is radiated heat from electric power conversion semiconductor(IGBT) stack effectively, now in the case of Japanese Fastec 360S, is using ram-air that is flowed in establishing cooling passage to propulsion system for cooling of condenser. In this research, it is that achieved the computing numerical analysis using ADINA of commertial program to examine flow characteristics and pressure distribution of ram-air for a condenser in cooling passage.

• Proceedings of the SAREK Conference
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• 2007.06a
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• pp.194-194
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• 2007

• Journal of the Korean Society of Visualization
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• v.17 no.2
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• pp.39-47
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• 2019

Impingement cooling utilizing synthetic jets is emerging as a popular cooling technique because of its high local cooling efficiency. The interaction between the vortex structure of the synthetic jet and the surface is crucial in understanding the mechanism of this technique. In this study, the impinging vortex structure and its advection are investigated by experiments with jet-to-surface spacing $2{\leq}H/D{\leq}7$, and synthetic jet Reynolds number $5120{\leq}Re{\leq}9050$. Using phase-locked particle image velocimetry, ensemble averaged (phase averaged) flow fields are obtained, and vortex identification and quantification techniques are applied. The shape, trajectory, and intensity change of the vortex are assessed. A sharp decline in the vortex intensity and the occurrence of a counter-rotating vortex at the impingement point are observed.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.8 no.4
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• pp.576-582
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• 1996

This work studies qualitative thermal characteristics of PCM cold storage medium container and its surrounding streams. Experimental parameters are initial PCM temperature and cold water flow rate. A mathematical modeling was establised to estimate temperature distribution and the cooling process. We found that the phase-change temperatures of PCM varies from 6 to $8^{\circ}C$ which is constant for other materials and that the dominant heat transfer resistance is that on the container side taking about 3/4 of the total resistance. The one dimensional mathematical model predicts experimental data quit well.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.334-336
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• 2009

An elastic-plasticity model during the austenitic decomposition was derived and implemented to incorporate the two important deformation behaviors observed during the phase transformations: the volumetric strain and transformation induced plasticity due to the temperature change and phase transformation. To obtain transformed phase volume fractions during cooling, the fourth order Runge-Kutta method was used to solve the Kirkaldy's phase kinetics model which is function of temperature, austenitic grain size and chemical composition. The volumetric strain was calculated by considering the densities of constituent phases, while the transformation induced plasticity was based on the micro-plasticity due to the volume mismatch between soft austenitic phase and other harder phases. The constitutive equations were implemented into the implicit finite element software and a simple boundary value problem was chosen as a model problem to validate the effect of transformation plasticity on the deformation behavior of steel under cooling from high temperature. It was preliminary concluded that the transformation plasticity plays a critical role in relaxing the developed stress during forming and thus reducing the magnitude of springback.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1746-1750
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• 2004

The objective of this study is to investigate the effect of supercooling repression on the clathrate compound by adding additives. For this purpose, phase change temperature and supercooling were measured when additives added to TMA30wt% clathrate for heat source temperature of $-6^{\circ}C$. The experimental results show that the phase change temperature with the chloroform of 0.1wt% is higher by $0.3^{\circ}C$ than TMA30wt% and the supercooling with the surfactant 0.1wt% is reduced by $9.2^{\circ}C$.

• International Journal of High-Rise Buildings
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• v.6 no.2
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• pp.197-205
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• 2017

The conflict between indoor environmental quality and energy consumption has become an unneglectable problem for highrise office buildings, where occupants' productivity is highly affected by their working environment. An effective Façade, therefore, should play the role of an active building skin by adapting to the ever-changing external environment and internal requirements. This paper explores the energy-saving and indoor environment-improving potential of a phase-change material (PCM) integrated Façade. Building performance simulations, combined with parametric study and sensitivity analysis, are adopted in this research. The result quantifies the potential of a PCM-integrated Façade with different configurations and PCM properties, taking as an example a south-oriented typical office room in Shanghai. It is found that a melting temperature of around $22^{\circ}C$ for the PCM layer is optimal. Compared to a conventional Façade, a PCM-integrated Façade effectively reduces total energy use, peak heating/cooling load, and operative temperature fluctuation during the periods of May-July and November-December.