• Journal of the Korean Solar Energy Society
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• v.31 no.3
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• pp.80-88
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• 2011

Heliostat in the tower type solar thermal power plant is a sun tracking mirror system to reflect the solar energy to the receiver and the optical performance of it affects to the efficiency of whole power plant most significantly. Thus a solid understanding of heliostat's energy concentration characteristics is the most important step in designing of the heliostat field and the whole power plant. The work presented here is the analysis of energy concentration characteristics of heliostat used in 200kW solar thermal power plant, where the receiver located at 43m high in tower has $2{\times}2$m rectangular shape. The heliostat reflective surface is formed by 4 of $1{\times}1$m flat plate mirror facet and the mirror facet is mounted on the spherical frame. The direct normal incident radiation models in vernal equinox, summer solstice, autumnal equinox and winter solstice are first derived from the actually measured data. Then the intercept ratio, heat flux distribution and total energy collected at the receiver for the heliostats located in the various places of the heliostat field are investigated. Finally the effect of mirror facet installation error on the optical performance of the heliostat is analyzed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.3
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• pp.201-209
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• 2009

The objective of present research work is to design the heat conductive mould to improve cooling characteristics of the injection mould for a mouse. In order to obtain the high cooling rate of the mould, a heat conductive mould with three different materials was designed. The materials of the base structure, the mid-layer and the molding part of the heat conductive mould were chosen as Cu-Ni alloy (Ampcoloy 940) to improve the heat conductivity of the mould, Ni-Cu alloy (Monel 400) to reduce a thermal stress, injection tool steel (P21), respectively. Through the three-dimensional transient heat transfer analysis and the thermal stress analysis, the effects of the geometrical arrangement of each material on the cooling characteristics and the thermal stress distribution were examined. From the results of the analyses, a proper design of the thermal conductive mould was obtained.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.4
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• pp.321-325
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• 2020

Atmospheric environmental problems have a major impact on human health and lifestyle. In humans, inhalation of nitrogen oxides causes respiratory diseases, such as bronchitis. In this paper, thermal analysis of a gas sensor was carried out to design and fabricate a wearable nylon-yarn gas sensor for the detection of NO_x gas. In the thermal analysis method, the thermal diffusion process was analyzed while operating the sensors at 40 and 60℃ to secure a temperature range that does not cause thermal runaway due to temperature in the operating environment. Thermal diffusion analysis was performed using the COMSOL software. The thermal analysis results could be useful for analyzing gas adsorption and desorption, as well as the design of gas sensors. The thermal energy diffusion rate increased slightly from 10.05 to 10.1 K/mm as the sensor temperature increased from 40 to 60℃. It was concluded that the sensor could be operated in this temperature range without thermal breakdown.

• Proceedings of the KIEE Conference
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• 2001.04a
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• pp.397-400
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• 2001

In eddy, current brake system(BS), high current may flow for increase of braking force within a short time. Therefore, the estimation of thermal characteristics for BS is required. In this paper, the thermal characteristics of eddy-current brake for the Korean high speed train are analyzed by using 2-dimensional Finite Element Method (2D-FEM) and measured.

• Textile Coloration and Finishing
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• v.24 no.3
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• pp.204-212
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• 2012

This study was used a thermogravimetric analyzer to determine thermal characteristics, a hair analysis system to examine morphological changes of wefts-human hair, poly vinyl chloride(PVC) and polyethylene terephthalate (PET)-used in manufacturing wigs. According to a flammability test on human hair and synthetic wefts for wigs, the best results were observed in human hair. According to a thermal test, PET was the best in terms of thermal stability. Also good tensile strength was observed as well. In a scanning electron microscope observation, no human hair scale layer was found because of chemical treatment. In the PVC sample, homogeneous unevenness was observed. Due to a lack of human hair supply and increase in its price, recently, PET weft has emerged as a great substitution for human hair. Because it can be curled using an electric curling device and is more efficient than the conventional non-flammable material PVC in terms of thermal resistance, it will become the next-generation weft for wigs.

• Journal of Welding and Joining
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• v.19 no.5
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• pp.499-505
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• 2001

In order to classify the mechanical phenomena of thermal elasto-plastic behavior on the multi-spot welded joints, this study has tried to carry out three-dimensional thermal elasto-plastic analysis on them. However, because the shape of multi-spot welded joints is not taxi-symmetric, unlike the cafe of single-spot welded joint, the solution domain for simulation should be three dimension. Therefore, in this paper, firstly, the three-dimensional thermal elasto-plastic program is developed by an iso-parametric finite element method. Secondly, from the results analyzed by developed program, this has clarified mechanical characteristics and their production mechanism on single and multi-spot waled joints. Moreover, it has been intended to make clear effects of pitch length on welding residual stresses, plastic strain of multi-spot welded joints.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.402-405
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• 2002

This paper presented the characteristic of Heat-transfer on the winding composed with Epoxy-resin in a 50 kVA cast-resin dry type transformer The resin cast transformer is used widely in supplying electricity systems. However, to know the thermal characteristics of that is very useful in designing, manufacturing, and maintaining, there is no pertinent method to calculate this. In this paper, Based on the results of the physical characteristics and the simulation by commercial software using FEM method, we established the Prototype Model for this. According to that Model, an analysis on a variation of the hottest spot temperature was discussed as a function of thermal conductivity for the individual windings composed with Epoxy-resin. The thermal conductivity of the individual windings with reference to upper way was discussed.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.4
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• pp.648-656
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• 2004

In this study, a highly efficient shell-and-tube heat exchanger with plate fins is considered to improve thermal performance of the conventional shell-and-tube heat exchanger. This type of shell-and-tube heat exchanger with plate fins of various shape is simulated three-dimensionally using a commercial thermal-fluid analysis code. CFX4.4. The effect of the shape of the plate fin on heat transfer characteristics is also investigated by the simulation. Plate fins of four different shapes. plane, plane-slit. wave. and wave-slit fins, are considered. The flow fields, pressure drop and heat transfer characteristics in the heat exchanger are calculated. It is proved that the shell-and-tube heat exchanger with plate fins is superior to the conventional shell-and-tube heat exchanger without plate fins in terms of heat transfer. The shape of the plate fin is important in the performance of a heat exchanger such as heat transfer and pressure drop.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.1
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• pp.42-47
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• 2014

The use of BLDC motor in Vehicle and industrial field, it is operated by continuous and intermittent driving. When the intermittent driving is occurred by the rise and fall of temperature repeatedly, it was represented by different characteristics in case of continuous driving. So, it is very important that heat source estimation according to the duty ratio. In this paper, temperature characteristics according to the operating method of BLDCM was calculated by using the thermal equivalent circuit, and the validity of the study was demonstrated as compared to the calculated and experimental results.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.2
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• pp.33-40
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• 1997

Recently, there are an increasing needs for high speed rotating spindle which is an important mechanical ele- ment for a high efficiency machine tool in order to shorten machining time and cut production costs. The heat gen- eration is the most important problem in the motor integrated spindle. In this study, the effects of temperature distribution and thermal behavior according to the oil-air lubrication and cooling conditions are investigate theo- retically and experimentally on the motor-integrated spindle under unloading condition. The experimental spin- dle system is composed with the angular contact steel ball bearings, oil-air lubrication, air or oil jacket cooling system. To analyze the thermal behavior and cooling characteristics for the motor integrated spindle, the analysis using the finite element method is carried out. The analytical results are compared with the experimental results.