• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.1
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• pp.77-83
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• 2004

In this study, the spray cooling heat transfer and working characteristics of the screen wick heat pipe with ultrasonic spray cooling system in condenser were experimentally investigated. The heat pipe was made of copper tube 300 mm long with inner diameter of 11.1 mm. The evaporator and condenser lengths of heat pipe were 40, 200 mm and the wick structure consists of two layer of 100 mesh copper screen. The experimental results show that the ultrasonic spray cooling increases the heat transfer rate on the condenser surface, and the total thermal resistance of heat pipe system decreases remarkably. A comparison is made for the two working fluids, water and ethanol. The surface temperature of the ethanol tube in evaporator section becomes higher than that of the water tube. Thus, the experimental result shows that water is more useful than ethanol as the working fluid because of increasing the operational limit within this experimental conditions.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.05a
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• pp.140-141
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• 2021

Arc thermal spray process is widely used to protect the steel from corrosion and abrasion. In the present study, two different coatings i.e. Al and Al-5%Mg were used to compare their corrosion resistance performance and the effect of 5% Mg addition in the properties of deposited coating. The SEM results showed the more compact and less porous morphology of Al-5%Mg coating compared to Al. The corrosion resistance performance of both deposited coatings was studied in artificial ocean water with exposure periods and results are compared. The total impedance values of Al-5%Mg at 0.01 Hz exhibited highest with exposure periods might be attributed to the coating and corrosion products nature and morphology compared to Al coating.

• Journal of the Korean Society of Clothing and Textiles
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• v.20 no.4
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• pp.565-572
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• 1996

The purpose of this study was to measure partial heat resistance of Hanbok when it worn. Since Hanbok varies from season to season, four different set of Hanboks (R, SN, p and S) were tested. Also Durumagi (D) which is worn over Hanbok (5) to keep warm from winter cold was tested as well. The thermal manikin was used in this experiment. The room temperature, air velocity and the relative humidity was set at $20\pm0.5^{\circ}C$, 0.15 m/sec and $50\pm$5% respectively. The mean skin temperature of the manikin was set at $33\pm0.5^{\circ}C$. The results were as follows: 1. The order from the least total heat resistance to the most was SN, R, p, 5 and D. 2. Upper arms had the highest heat resistance among the 13 parts. The next was abdomen thighs, buttock, legs, forearms and chest, back, and head, the order from the most to the least.

• Polymer(Korea)
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• v.24 no.6
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• pp.777-786
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• 2000

Fire resistance and thermal stability of polypropylene composite systems were investigated by using several halogenated fire-retardants such as decabromodiphenyl oxide (DBDPO) and chlorinated paraffin wax (CPW). The fire resistance of composite systems was thoroughly examined by measuring limited oxygen index (LOI, ASTM D2863, ISO 4589) and characteristic properties of cone calorimetry(ASTM E1354, ISO 5660) heat release rates (HRR), time to ignition (TTI), total heat release (THR), effective heat of combustion (EHC), mass loss rates, etc. Comparing the cone calorimetry experimental results of the halogen flame retardants, DBDPO exhibited twice higher efficiency than CPW in polypropylene systems, and the LOI also showed similar trends to cone calorimetry. The thermo-oxidative stability of the composite systems was increased about 30-5$0^{\circ}C$ in thermogravimetry analysis.Collectively, the combustion, extinction and thermally-stable characteristics of flame retardants were identified in this study.

• Proceedings of the KSR Conference
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• 1998.05a
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• pp.580-587
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• 1998

For many decades, the railway was constructed using tracks with jointed rails of relatively short lengths in accordance with rolling and handling technology. The joints cause many drawbacks in the track and lead to significant maintenance cost. So, railroad engineers became interested in eliminating joints to increase service loads and speeds by improving rolling, welding, and fastening technology, Continuous welded rail(CWR) track has many advantages over the conventional jointed-rail track. But in the case of the elimination of rail joints, it may cause the track to be suddenly buckled laterally by thermal and vehicle loads. Thermal loads are caused by an increase in the temperature of railway track. In this paper, CWR track model and CWRB program are developed for linear buckling analysis using finite element method(FEM). The finite element discretization is used with a total of 14 degrees of freedom for each rail element. The stiffness of the fastener, tie, and ballast bed are included by a set of spring elements. The investigation on the buckling modes and temperature of CWR track is presented in the paper.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.320-323
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• 2005

This paper discusses heat problem of IC, which composes the electronic instruments, to guarantee reliability of electronic instruments. And also proposes the unified equivalent model for various electronic instrument products to guarantee reliability and life of its parts. Because electronic instruments are down sizing and operated with high frequency, the internal temperature of electronic instruments is rising steadily. The internal temperature of the electronic instruments gives a big effect to electronic instrument's reliability and life. The semiconductor parts are the representative heat generation parts because of its complicated function, high frequency and high density. Consequently, guaranteeing reliability and life of electronic semiconductor is the important start point in securing the reliability and life of the electronic instrument product. Unfortunately, there are many factors, which affect heat dissipation efficiency. The heat dissipation efficiency follows the environment where the electronic instrument products are used. Therefore it is very difficult to define reliability and life of the electronic manufactures. Electronic instrument products are composed of printed circuit board (PCB), integrated circuit (IC), resistance, and capacitor and so on. And there are superposed thermal resistances, because the parts are arrayed on the printed circuit board (PCB), Therefore the total thermal resistance is variable. Consequently it cannot have same thermal model for each electronic instrument products. In the next part, we propose the unified equivalent model for various electronic instruments. And using the proposed equivalent model proofs the method for analysis reliability of electronic parts.

• Journal of the Korean Institute of Gas
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• v.17 no.1
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• pp.35-41
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• 2013

In this study, flame retardancy of polyurethane foam and phenolic foam were investigated by addition of phosphorous flame retardants. The thermal degradation behavior of polyurethane foam and phenolic foam in the presence of flame retardants has been studied by thermogravimetric analysis(TGA). Heat release rate(HRR), mean HRR, mass loss rate(MLR), total smoke released(TSR) and limited oxygen index(LOI) were tested by cone calorimeter. From the test results, Phenolic foam showed low HRR, MLR and TSR than polyurethane foam.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.3
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• pp.165-173
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• 2013

Core loss has a major effect on heat generation in synchronous motors with surface-mounted permanent magnets (SPMs). It is essential to perform heat transfer analysis considering core loss in SPM because core loss is seriously affected by torque and speed of motors. In the present study, mechanical loss, core loss and coil loss are evaluated by measuring input and output energies under various driving conditions. For a better understanding heat transfer paths in synchronous motors, we developed a lumped thermal system analysis model. Subsequently, heat transfer analysis has been performed based on acquired energy loss, temperature data and thermal resistance with three types of SPM. It is shown that the torque constants decrease by Max. 10% as speed increase. At the rated torque, the core loss is Max. 10.9 times greater than the coil loss and the hysteresis loss of magnets is dominant in total loss.

• Computers and Concrete
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• v.2 no.4
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• pp.249-266
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• 2005

In the present paper a transient three-dimensional thermo-mechanical model for concrete is presented. For given boundary conditions, temperature distribution is calculated by employing a three-dimensional transient thermal finite element analysis. Thermal properties of concrete are assumed to be constant and independent of the stress-strain distribution. In the thermo-mechanical model for concrete the total strain tensor is decomposed into pure mechanical strain, free thermal strain and load induced thermal strain. The mechanical strain is calculated by using temperature dependent microplane model for concrete (O$\check{z}$bolt, et al. 2001). The dependency of the macroscopic concrete properties (Young's modulus, tensile and compressive strengths and fracture energy) on temperature is based on the available experimental database. The stress independent free thermal strain is calculated according to the proposal of Nielsen, et al. (2001). The load induced thermal strain is obtained by employing the biparabolic model, which was recently proposed by Nielsen, et al. (2004). It is assumed that the total load induced thermal strain is irrecoverable, i.e., creep component is neglected. The model is implemented into a three-dimensional FE code. The performance of headed stud anchors exposed to fire was studied. Three-dimensional transient thermal FE analysis was carried out for three embedment depths and for four thermal loading histories. The results of the analysis show that the resistance of anchors can be significantly reduced if they are exposed to fire. The largest reduction of the load capacity was obtained for anchors with relatively small embedment depths. The numerical results agree well with the available experimental evidence.

• Korean Journal of Human Ecology
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• v.18 no.5
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• pp.1087-1092
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• 2009

From the environmental adaptation point of view, the clothing habits made by the thermal sensation and clothing weight of elderly women have changed according to the thermal sensation and health condition. The purpose of this study was to obtain the basic data for developing healthy and comfortable clothing for elderly women. Clothing weight, thermal sensation, clothing microclimate, resistance to cold and heat of 198 elderly women in Taejeon were surveyed from October 9, 2007 to October 19, 2007. 1. Clothing weight per body surface area was $830.4g/m^2$ of total clothing weight, $242.8g/m^2$ of underwear clothing weight, $617.3g/m^2$ of outerwear clothing weight, $419.8g/m^2$ of upper clothing weight, and $420.4g/m^2$ of lower clothing weight. 2. More than 90% of the respondents replied that they felt comfortable when the temperature inside the clothing was $33.5^{\circ}C$ and humidity inside the clothing was 30.2%. 3. The elderly women were more sensible to cold than to hot, those who felt cold had a tendency to wear heavier clothing. 4. The appeal rate for physical pain of older and lower income people, especially those with an income under 1,000,000 won, was higher than that of others. On the other hand, the lower the subjective economic level, the younger they were, and the more the monthly average income was, the higher the rate of mental pain. 5. The heavier the total clothing weight was, the higher the appeal rate for general pain.