• 한국태양에너지학회 논문집
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• 제24권3호
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• pp.39-46
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• 2004

In this paper, thermodynamic design data for heating of double-effect absorption system using LiCl-water for evaporator heating source of sofar energy are investigated for the water-LiCl pair and a comparative study of the water-LiCl pair with the water-LiBr pair is given used for the computer simulation. The computer simulation is based on mass, material and heat balance equations for each part of the system. Coefficients of performance and flow ratios for effects of different operating temperatures are investigated. It is found that the heating COP is higher for the water -LiCl pair than for the water-LiBr pair, and FR is lower for the water-LiCl pair than for the water LiBr pair.

• 소성∙가공
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• 제31권2호
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• pp.96-102
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• 2022

The multi-point dieless forming technology is one of flexible forming technologies that can form 3D curved surfaces of various shapes utilizing a lot of punch arrangements. A new technology that can simultaneously apply high-temperature forming and flexible forming technology by fusing local heating effect to such multi-point dieless forming technology was proposed in the present study. A simple local heating multi-point dieless forming apparatus was fabricated to confirm the applicability of this new technology. This equipment was designed to be used as a heat source by inserting heating cartridges in the head of the multi-point punch. Cartridges were used for all individual punches. Using the manufactured equipment, the time to raise the temperature to the target temperature and the surface temperature of the punch head part in contact with the plate were measured. In addition, forming experiments were carried out according to sheet material temperature (100 ℃, 200 ℃, and 300 ℃) to obtain forming results for each condition. The applicability and feasibility of this technology were confirmed through experimental results.

• Applied Microscopy
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• 제34권1호
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• pp.23-29
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• 2004

본 연구에서는 에너지 여과장치와 직접 고온 가열 장치를 이용하여 실리카 나노입자의 비정질 구조 분석과 가열실험을 통한 구조변화에 대해 연구하였다. 실리카 나노입자의 전자회절도형은 세 개의 diffuse한 ring으로 구성이 되어 있으며, $900^{\circ}C$의 온도에서 실리카 나노입자는 서서히 결정화가 이루어짐을 알 수가 있었다. 세 개의 diffuse한 ring은 비정질 실리카 구조가 $SiO_4$ tetrahedra가 구조의 기본 단위로 이루어졌으며, 가열에 의해 이들이 점이적으로 tridymite 이상적인 층상 구조로 결정화되어 간다는 것을 이해할 수 있었다. 또한 전자현미경 내의 고진공하에서 $850^{\circ}C$ 이상의 온도 가열로 인해 $SiO_2$로부터 증발된 SiO가 grid에 재증착되는 것을 관찰할 수 있었고, 남아 있는 $SiO_2$는 전기로를 이용한 가열 실험결과와 같이 비정질 구조에서 orthorhombic trydimite로의 결정화가 이루어짐을 알 수 있었다.

• Journal of Welding and Joining
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• 제34권2호
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• pp.46-53
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• 2016

Effect of heating rate on microstructure of brazed joints with STS 304 Printed Circuit Heat Exchanger (PCHE),which was manufactured as large-scale($1170(L){\times}520(W)){\times}100(T)$, mm), have been studied to compare bonding phenomenon. The specimens using MBF 20 was bonded at $1080^{\circ}C$ for 1hr with $0.38^{\circ}C/min$ and $20^{\circ}C/min$ heating rate, respectively. In case of a heating rate of $20^{\circ}C/min$, overflow of filler metal was observed at the edge of a brazed joints showing the height of filler metal was decreased from $100{\mu}m$ to $68{\mu}m$. At the center of the joints, CrB and high Ni contents of ${\gamma}$-Ni was existed. For the joints brazed at a heating rate of $0.38^{\circ}C/min$, the height of filler was decreased from $100{\mu}m$ to $86{\mu}m$ showing the overflow of filler was not appeared. At the center of the joints, only ${\gamma}$-Ni was detected gradating the Ni contents from center. This phenomenon was driven from a diffusion amount of Boron in filler metal. With a fast heating rate $20^{\circ}C/min$, diffusion amount of B was so small that liquid state of filler metal and base metal were reacted. But, for a slow heating rate $0.38^{\circ}C/min$, solid state of filler metal due to low diffusion amount of B reacted with base metal as a solid diffusion bonding.

• 한국융합학회논문지
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• 제10권7호
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• pp.169-174
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• 2019

자동차 운전석의 따뜻하고 쾌적한 요구가 증가하고 있기 때문에 난방 시트의 연구 개발이 활발히 이루어지고 있다. 본 연구에서는 세 가지의 난방 시트 모델 A, B, C를 가지고 열응력해석과 구조해석을 시행하였다. 똑같은 재질로 열해석을 함으로서, 연구 결과에서는 모델 A가 모델 B나 모델 C보다 더 좋은 열전달을 가짐을 보여주었다. 이로써 모델들이 제품의 형상에 따라 같은 재질을 가졌다고 하더라도 열전달들이 서로 다른 것을 알 수 있었다. 더 안정적인 난방을 기대하기 위해 열선을 추가하는 것은 더 좋은 난방이 될 수 있지만 제품의 가격대비 성능을 고려한 측면에서 한계가 있다. 전반적으로 모든 면에서 모델 B가 모델 A나 모델 C보다 열적으로 가장 안전하다고 사료된다. 본 연구결과에 의하여 취득한 내구성과 안정성 있는 자동차 난방 시트 제품의 설계데이터를 사용하여 자동차 운전석에 융합하여 그 예술적인 분위기를 조성할 수 있다.

• 한국전기전자재료학회논문지
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• 제34권2호
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• pp.136-141
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• 2021

Heating cables, widely used in office buildings, factories, streets and railways, deteriorate in electrical insulation during operation. The insulation deterioration of heating cables leads to electric discharges that can cause electrical fires. With this background, this paper dealt with a condition monitoring technique for heating cables by the analysis of discharge signals to prevent electrical fires. Insulation deterioration was simulated using an arc generator specified in UL1699 under AC operation, and the characteristic and propagation of discharge signals were analyzed on a 100 meter-long heating cable. Discharge signals produced by insulation deterioration were detected as a voltage pulse because they are as small as a few mV and they are attenuated through propagation path. The frequency spectrum of discharge signals mainly existed in the range from 70 kHz to 110 kHz, and the maximum attenuation of the signal was 84.8% at 100 meters away from the discharge point. Based on the experimental results, a monitoring device, which is composed of a high pass filter with the cut-off frequency of 70 kHz, a comparator, a wave shaper and a microprocessor, was designed and fabricated. Also, an algorithm was designed to discriminate the discharge signal in the presence of noise, compared with the pulse repetition period and the number of pulse counts per 100ms. In the experiment, the result showed that the prototype monitoring device could detect and discriminate the discharge signals produced at every discharge point on a heating cable.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2014년도 춘계 학술논문 발표대회
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• pp.150-151
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• 2014

A mold of free-form concrete segment can be used only one time. Thus, the construction duration and cost are increased. The materials of the mold such as wood and metal have limitations due to the implementation and reuse. The review of the material of the mold for free-form concrete segment is needed to reduce duration and production cost. Phase change material can be used both to implement free-shape by heating and to produce mold after cooling. After using Phase change material can be re-used to mold by heating. The scope of this study is many kind of phase change materials for molding. The aim of this study is to analyze the phase change materials for production of changable mold for free-form concrete segment. In this study, the paraffin wax that is melted at 64℃ was selected by considering both the energy efficiency and the weather of Korea.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집
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• pp.366-370
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• 2002

GaAs has become a very popular material for the fabrication of high frequency, low noise and microwave power devices. GaAs devices are also well suited for high temperature operation because of the large band gap of this material. The standard GaAs technology and device structures have to be modified for stable operation at high temperature. In this paper, AlGaAs/GaAs HBT considering stable ohmic contact at high temperature as well as thermal effect such as self-heating effect are introduced. All the data obtained study will be used as input data for the simulator and the result will be compared with an analytical model available in this study,

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.1225-1230
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• 2004

The effects of substrate material on the local heating performance of microheaters are studied by both numerical analysis and experiment. Transient conduction analysis shows that the substrate material with low thermal conductivity is critical to the local heating and fast response. A measurement technique for surface temperature field in microscale is newly proposed, which uses temperature sensitive fluorescent dye coated on the surface. The measured surface temperature fields on microheater arrays fabricated on different substrates are presented.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 춘계학술대회논문집
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• pp.279-282
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• 2005

The aim of this study is to suggest the method of measuring the dynamic stiffness and loss factor of materials used under floating floors in the dwelling by korea standard (KS F 2868). According to the results, the amplitude change of an impact source have no effect on the variation of the dynamic stiffness and loss factor. Comparing with the heating before, heating makes lower the dynamic stiffness except the EPS. In EVA material, the loss factor is increased by heating.