• 에너지공학
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• 제26권4호
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• pp.57-66
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• 2017

열은 전력과 같이 이동속도가 빠르지 못하고 전력에 비해 손실이 비교적 크게 발생하므로 전력거래와 같이 한개의 운용센터를 두고 열 연계 시스템을 운용하는 것은 현실성이 없다. 현재 열 연계가 모두 이루어지고 있는 한국지역난방공사의 경우에도 인접한 2~4개 정도의 열병합발전소간에만 열 거래가 이루어지고 있는 실정이다. 따라서 본 논문에서는 열 거래를 위한 통합운용센터를 몇 개의 권역으로 나누어 각 권역마다 권역의 Hub 통합운용발전소를 두고 운용하는 것이 열매체의 특성을 반영하는데 적정하고 타당한 것으로 판단하여 집단에너지 사업자간 열 연계 메커니즘을 제안하였다. 제안된 메커니즘에 최적으로 열 거래를 행할 수 있는 알고리즘을 개발하고 이를 실제 사업자에 적용하여 제안한 알고리즘의 유용성을 검증하였다.

• 한국전기전자재료학회논문지
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• 제32권6호
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• pp.522-527
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• 2019

In order to fabricate high-quality SiC substrates for power electronic devices, various single crystal growing methods were prepared. These include the physical vapor transport (PVT) and top seeded solution growth (TSSG) methods. All the suggested SiC growth methods generally use induction-heating furnaces. The temperature distribution in this system can be easily adjusted by changing the hot-zone design. Moreover, precise temperature control in the induction-heating furnace is favorably required to grow a high-quality crystal. Therefore, in this study, we analyzed the heat transfer in these furnaces to grow SiC crystals. As the growth temperature of SiC crystals is very high, we evaluated the effect of radiation heat transfer on the temperature distribution in induction-heating furnaces. Based on our simulation results, a heat transfer strategy that controls the radiation heat transfer was suggested to obtain the optimal temperature distribution in the PVT and TSSG methods.

• Bulletin of the Korean Chemical Society
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• 제12권1호
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• pp.22-26
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• 1991

Potential energy surfaces for the proton transfer in a formamide dimer have been obtained by ab initio SCF calculations with STO-3G, 3-21G, and 4-31G basis sets and several features have been discussed. Energy minima for a formamide dimer and its tautomer are varied with basis sets. But the general features of the potential energy surfaces are similar among them.

• 에너지공학
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• 제24권3호
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• pp.128-134
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• 2015

본 연구는 연성체와 강체로 구성된 다물체 시스템을 분석한 것이다. 이송용 로봇은 주로 빠른 속도와 넓은 범위의 이동거리의 장점으로 무거운 부품으로 구성된 자동화산업에 사용된다. 주로 3축으로 구성되어 사용되는 이송용 로봇은 커다란 부하를 담당하기 위해 최근에 강도와 강성을 고려하여 개발되어진다. 따라서, 이러한 목적으로 과도모드가 적용된 동적해석을 수행하여 어느 시간과 위치에서 항복되는지 찾기 위해 수행되었다. 이러한 연구의 결과로 로봇의 응력과 변형량을 분석할 수 있었다.

• 한국환경과학회지
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• 제6권4호
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• pp.391-397
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• 1997

The study was carried out to demonstrate the superiority of used packing in view of energy saving and efficiency of mass transfer, comparing with conventional packing. The results are as follows : 1. Owing to low Pressure drop under high load. 25mm NSW-ring, pp. can cause energy saving 2. The unique magnitudes of used packing are as follows $C_G$=5.78, m=0.67, n=0.46 3. Used packing can make high efficiency including energy saving because of low pres sure drop per the number of transfer unit. To rate the characteristic of packing, It should be carried out that the measurement of pressure drop per packing height and per the number of transfer unfit. This study demonstrated the superiority of used packing by carring out above experiment and could be used as basic reference for design and predicting efficiency of packing tower which is tilled with same packing.

• Journal of Magnetics
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• 제18권2호
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• pp.105-110
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• 2013

The design model and key parameters of the material design for the control of induced magnetic flux at the near-field and efficient power transfer in a modified wireless power transfer (WPT) system with a large air gap of wireless electric vehicles were investigated through analytical simulations for magnetic vector and time-domain transient analysis. Higher saturation magnetic core with low core loss induced a stronger vertical magnetic field by the W-type primary coil in the WPT system with a gap of 20 cm at 20 kHz, which is shown from the vector potentials of the magnetic induction. The transient analysis shows that the higher magnetic fluxes through the pick-up cores lead to a linear increment of the alternating voltage with a sinusoidal waveform in the non-contact energy transfer system.

• 대한기계학회논문집
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• 제18권12호
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• pp.3305-3314
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• 1994

In this study, the influence of a frost formed on the vertical plate for different operating conditions(the temperature of the air, the humidity of the air, the velocity of the air, and the temperature of the cooling plate) is investigated. The performance of the heat exchanger is examined by introducing a parameter such as the energy transfer resistance. Correlations which relate frost density, frost thickness and energy transfer resistance to Reynolds number, air temperature and humidity, and cooling plate temperature are developed. Static pressure drop and air flow rate are expressed as a function of free flow area of air.

• 한국태양에너지학회 논문집
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• 제21권3호
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• pp.43-50
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• 2001

A horizontal mantle heat exchanger for a thermosyphon-driven SDHW(solar domestic hot water) was numerically simulated and fluid flow and heat transfer in the annulus of the mantle heat exchanger were quantitatively investigated. The Reynolds number, the location of the inlet, and the gap of the annulus were selected as the important design variables. The effects of the design variables on the heat transfer characteristics were thoroughly studied. Based on the numerical results, a correlation for predicting the heat transfer coefficient was suggested as the conclusion of this study.

• Bulletin of the Korean Chemical Society
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• 제23권8호
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• pp.1111-1115
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• 2002

The photoluminescence of calixarene crystals has been studied as functions of temperature, time, and concentration. The vibronic bands shift to longer wavelength and become significantly sharper as temperature decreases. The experimental results r eveal that the structural transformation occur during the annealing process. Time-resolved spectra of calixarene at 12 K are monitored. Spectral features, which demonstrate characteristic of energy transfer processes, are not observed. The depopulation of excited state density is mainly controlled by unimolecular decay process dominating other decay processes. The lifetime was found to be 2.6 $\pm$ 0.1 ns. For the case of calixarene mixed with naphthalene, the fluorescence spectrum shows that the band centered at 340 nm lies 2840 $cm^{-1}$ below the relatively broad 310 nm band found for calixarene crystals. The spectra also exhibit that the emission intensity increases with increasing calixarene concentration. The results are evident that the calixarene emission is quenched by the naphthalene. Phosphorescence of calixarene mixed with naphthalene crystals is observed to determine whether the emission is due to naphthalene. The phosphorescence peaks were compared with the ground-state vibrational frequencies of naphthalene and found to be in good agreement. The results indicate that inter-molecular energy transfer occurs between calixarene and naphthalene.

• Bulletin of the Korean Chemical Society
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• 제19권10호
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• pp.1063-1068
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• 1998

The nature of F electronic excitation energy transfer to OH- vibrational levels in KCl crystals is the exchange interaction, although the transfer process exhibits three temporally distinguishable components depending on the distance between excited F center and OH-. The critical distance as well as rate of the major energy transfer process in randomly distributed samples increases rapidly as OH- librational motions become active with temperature rise. The excited state character introduced into the OH- ground electronic state by perturbation is essential for the exchange interaction. The perturbation is brought about by the expanded electron cloud of excited F center for OH- associated to F center, whereas by librations and lattice vibrations perpendicular to the bond axis for isolated OH- . F excitation quenching efficiency by OH- is dependent on the variation of the critical distance rather than the rate as the rate is much faster than the normal F bleach recovery rate.