Papers by Author: Hee Sung Yoon

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Authors: Hee Sung Yoon, Ho Dong Yang, Yool Kwon Oh
Abstract: This study investigated on the cooling characteristics of AC4C aluminum alloy and AC7A aluminum alloy used as a casting material for manufacturing automobile tire mold by experiment. The metal mold device by gravity casting method was manufactured. AC4C casting material and AC7A casting material were heated in smelting furnace at about 650°C and 670°C, and then they injected into the metal mold device when the melting process was completely finished, respectively. When the melted casting material was completely injected into the metal mold device, the temperature inside the casting was measured by 9 measurement points. Also, when the temperature inside the casting was measured approximately 500°C during the cooling process, the casting is separated to metal mold device and carried out cooling at normal temperature. The separating time from metal mold device of AC4C casting material and AC7A casting material have been taken 25 minutes and 15 minutes, respectively. The final cooling time of AC4C casting material and AC7A casting material have been taken 400 minutes and 380 minutes, respectively. Accordingly, AC7A casting material is able to improve on productivity than AC4C casting material because production time was decreasing.
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Authors: Ho Dong Yang, Hee Sung Yoon, Yool Kwon Oh
Abstract: This study investigated on cooling characteristics of thermoelectric cooling system using thermoelectric materials as Bi-Te alloy. The thermoelectric module used as thermoelectric materials of thermoelectric cooling system can achieve heating and cooling by change of electricity direction. When thermoelectric module and cooling fan received 12V from DC power source, the cooling region was occurred in thermoelectric cooling system. Also, the piezoelectric actuator was applied to improve the cooling effect and investigate the heat transfer phenomenon. The temperature distribution of cooling region was measured to investigate cooling characteristics of thermoelectric cooling system. The flow phenomenon of cooling region was visualized using visualization device such as He-Ne laser, optical lens, image grabber and CCD camera. When the piezoelectric actuator was applied to the heat transfer process of thermoelectric cooling system, acoustic streaming was occurred in the cooling region. The acoustic streaming was occurred forced convection flow, and was regularly formed the temperature distribution in the cooling region. In the end, the results clearly show that the acoustic streaming is one of the prime effects to enhance the convection heat transfer and cooling effect.
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Authors: Yool Kwon Oh, Young Sun Kim, Hee Sung Yoon
Abstract: This study was numerically and experimentally investigated on improvement capture velocity for increasing inhalation efficiency of hood in local ventilation system. The inhalation efficiency of hood was studied to improve by increasing inhalation force of the hood that attached the new device named “Gas-Guide-Device (GGD)”. Also, harmful material that couldn’t inhale in hood was removed by increasing capture velocity at the edge of hood. For the numerical study, computational fluid dynamic (CFD) was used to predict the improvement of flow velocity with attached GGD in hood. To verify the numerical result, the flow velocity was experimentally measured using a hot-wire type anemometer. As a result of the numerical and experimental study for improving the effect of the GGD on the inhalation efficiency of the hood, it was verified that the capture velocity around the hood inlet was relatively higher for the hood with the GGD than for the one without it.
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Authors: Hee Sung Yoon, Young Sun Kim, Yool Kwon Oh
Abstract: In this study, numerical analysis applying the finite element method (FEM) was used to investigate the effect of heat flux and temperature on thermal strain of aluminum alloy casting mold. For numerical analysis, analysis model was considered the effect of shrinkage, rapid temperature variation on the casting mold and was applied the temperature calibration to reduce the deformation and stress by temperature difference of inside and outside the mold during the cooling process. In detail, temperature, deformation and stress distributions occurred inside of casting mold predicted by numerical method and then investigated the correlations between the heat flux and temperature variation during the cooling process. As a result, aluminum alloy casting mold is occurred deformation and stress because of rapid temperature difference in the initial of cooling, but it can be reduced the thermal strain through the heat flux control and temperature calibration. Accordingly, the technique of this numerical study will be helped to make the effective and the good quality of casting mold products.
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