• 한국안전학회지
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• 제38권3호
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• pp.27-34
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• 2023

With the technological development of the semiconductor industry, the roles of electrical and thermal energy supply and control of semiconductor equipment in ultrafine processes have become very important. However, instances of electrical fires in the chiller heater, which is used for cooling in the semiconductor manufacturing process, are increasing. A fire occurs in combustibles due to high heat at the connection part of the chiller heater, that is, when the number of electrical wires in the connection part is reduced or when the wires are completely disconnected. In this study, the temperature characteristics were compared and analyzed through experiments and 3D simulations. The number of electrical wires, which is the connection part of the chiller heater, was reduced by 90%, 50%, 30%, 10%, and 5%, and the wires were completely disconnected. When the number of electrical wires was reduced by 5%, heat of up to 80℃ was generated, which is a relatively high temperature but insufficient to cause a fire in combustibles. Complete disconnection occurred due to the vibration of the motor and other components, and sparks and arcs were generated, resulting in a rapid increase in temperature to up to 680℃. When completely disconnected, the temperature increase was sufficient to cause a fire in the combustibles covering the terminal block. Therefore, in this study, the causes of electrical fires in chiller heaters were investigated and preventive measures were proposed by analyzing abnormal signals and thermal characteristics caused by the electrical wiring being reduced and completely disconnected.

• 한국기계가공학회지
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• 제16권2호
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• pp.81-87
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• 2017

The pipe connection process using a clamping ring is used for joining small pipes in the refrigerator and air-conditioner industries instead of the brazing process, which induces inevitable thermal deformation in the pipes. However, few studies have been carried out on the process to select optimal parameters in joining pipes, and studies on the relation between the process parameters of the connection and connecting force of the joint have not been conducted. In this study, the connection process of pipes with the clamping ring was modeled using the finite element method (FEM) and analyzed to obtain the contact stress distribution between the pipes with which the connecting force of the joint was estimated. Considering the characteristics of pipe connection, the process was modeled and simulated in a two-dimensional axisymmetric solution domain. With the numerical model, the effect of ring shape on the connection was studied by adding a projection to the end of a ring or changing the length of a ring. The results of the analyses revealed that the contact stress distribution could be predicted with the suggested model. The effect of the ring shape was also presented. The effect of any combination of process parameters could be easily estimated through the related analyses.

• 한국자동차공학회논문집
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• 제22권5호
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• pp.44-49
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• 2014

As expansion and contraction of bike disk brake are happened continuously by temperature at repeated urgent braking. In this study, 3 kinds of model are designed according to configurations of holes and thermal durabilities on bike disk brake are investigated by comparing 3 models through temperature and thermal analyses. Maximum thermal stress happened at the disk contacted with pad and the connection part fixing disk rotor. Instead of initial state, the temperature is uniformly distributed at transient state. As the area of hole at disk rotor face becomes wider, thermal stress becomes lower at the initial state. On the other hand, in case the number of holes increases, thermal stress becomes lower at the elapsed time of 100 seconds. The thermal durability of bike disk brake can be improved by applying this study result with configurations of holes.

• 설비공학논문집
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• 제15권1호
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• pp.32-39
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• 2003

Thermal comfort in the Rotunda which is high wide visiting space of the new national museum of Korea has been numerically investigated in this paper. To evaluate thor-mal comfort of the Rotunda, well-known indices, PMV and PPD were introduced. The results of present investigation show that thermal comfort is satisfied at the breathing zone of the visiting space. However a thermal stratification with $9^{\circ}C$ of temperature difference occurs along the height of the Rotunda which makes the thermal environment worse. For example, the PPD value reaches up to 50% in the 6th floor connection passage. Consequently, additional HVAC design factors should be considered in order to reduce the large thermal stratification.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.694-699
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• 2002

In autobody assembly, thin-wall, tubular connections have been used for the frame structure. Recent interest in light materials, such as aluminum or magnesium alloys, has been rapidly growing for weight reduction and fuel efficiency. Due to higher thermal expansion coefficient, low stiffness/strength, and low softening temperature of aluminum and magnesium alloys, control of welding-induced distortion in these connections becomes a critical issue. In this study, the material sensitivity to welding distortion was investigated using a T-tubular connection of three types materials; low carbon steel (A500 Gr. A), aluminum alloy (5456-H116) and magnesium alloy (AZ91C-T6). An uncoupled thermal and mechanical finite element analysis scheme using the ABAQUS software program was developed to model and simulate the welding process, welding procedure and material behaviors. The predicted angular distortions were correlated to the cumulative plastic strains. A unique relationship between distortion and plastic strains exists for all three materials studied. The amount of distortion is proportional to the magnitude and distribution of the cumulative plastic strains in the weldment. The magnesium alloy has the highest distortion sensitivity, followed by the other two materials with the steel connection having the least distortion. Results from studies of thin-aluminum plates show that welding distortion can be minimized by reducing the cumulative plastic strains by preventing heat diffusion into the base metal using a strong heat sink placed directly beneath the weld. A rapid cooling method is recommended to reduce welding distortion of magnesium tubular connections.

• KIEAE Journal
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• 제15권6호
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• pp.11-18
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• 2015

Purpose: The current study analyzed trends in thermal insulation performance with aging, and condensation characteristics caused by the former. Method: Thermal insulation and condensation prevention performance of an architecture were assessed using Temperature Difference Ration Inside, or TDRi. Subjects of this quantitative analysis in thermal insulation performance change due to aging included recently constructed apartments and aged apartments older than 40 years. Time series comparison and analysis were conducted to observed changes in the thermal insulation performance and condensation characteristics. Result: Analysis showed that wall insulation performance degraded with aging regardless of fortified insulating material usage or insulating material type, which caused increased danger of condensation. In addition, when fortified insulating material was installed on the connection between the walls, insulation performance degradation was lower compared to cases in which fortified materials were not used. In all cases from 1 to 10, the rate of thermal insulation performance degradation increased after 20 years of aging.

• 천문학회지
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• 제37권5호
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• pp.583-587
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• 2004

With the aim to investigate the statistical properties and the connection between thermal and non-thermal properties of the ICM in galaxy clusters, we have developed a statistical magneto-turbulent model which describes, at the same time, the evolution of the thermal and non-thermal emission from galaxy clusters. In particular, starting from the cosmological evolution of clusters, we follow cluster. mergers, calculate the spectrum of the magnetosonic waves generated in the ICM during these mergers, the evolution of relativistic electrons and the resulting synchrotron and Inverse Compton spectra. We show that the broad band (radio and hard x-ray) non-thermal spectral properties of galaxy clusters can be well accounted for by our model for viable values of the parameters (here we adopt a EdS cosmology).

• 국제초고층학회논문집
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• 제3권2호
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• pp.147-154
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• 2014

The purposes of this study were to analyze criteria for measurement chamber design dedicated curtain wall, and how to measure of performance configuration and status of the chamber that is currently being used. Main dealing criteria is AAMA 1503-09. Measurement of data is made in curtain wall Mock-up experiment station with thermal imaging camera. Measurement data using thermal imaging cameras at Mock-up curtain was made at the test site. The results of this study were as follows; There is no U-value test method for actual size of curtain wall. The thermal test outdoor chamber showed heat loss in the connection part of indoor and outdoor chamber. And the indoor chamber showed unstable temperature distribution by height.

• 센서학회지
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• 제8권1호
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• pp.89-94
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• 1999

In this study, a new technology to bond the PZT with connection board, which is a core technology for the fabrication of medical micro high frequency sensors, was developed. Two technologies were adopted. One is bonding of In using thermal heating, he other is bonding of Pb using a high frequency heating machine. In case of thermal eating, bonding was failed because of the contaminations of In surface. But, when using high frequency healing machine, we developed good bonding characteristics at various experimental conditions and thickness of the electrode material.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 하계학술대회 논문집
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• pp.136-139
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• 2000

Epoxy materials are used as insulation material for electric power cables. In the case of a flow of excess current due to the temperature difference which occurs between the heat of the conductor and the atmosphere, heat degrades connection point of the cables. Also, the mechanical stress, which occurs due to the thermal expansion coefficient of cable connection electrode system and epoxy insulation materials along with the gap between thermal conduction based on the extra high voltage of transmitted voltage, increases possibility of cracks to occur. The relationship between mechanical stress and electrical breakdown mechanism is verified for the epoxy materials such as high toughness epoxy materials, which comes to be used contemporarily, and for the breakdown mechanism of epoxy materials on the multi-stresses (mechanical and electrical) due to the variation of the temperature.