• Title/Summary/Keyword: Energy Transfer

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Study on Heat Transfer and Fouling of Flow Boiling Systems using Oxidized Graphene Nanofluid (유동 비등 시스템에서 산화 그래핀 나노유체의 열전달 및 파울링에 대한 연구)

  • Kim, Woo-Joong;Kim, Nam-Jin
    • Journal of the Korean Solar Energy Society
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    • v.36 no.3
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    • pp.63-74
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    • 2016
  • The nanofluids are the fluids with excellent thermal property, it is expected as a working fluid of the next generation. The nanofluids are well known that if it is used in the boiling heat transfer system, the critical heat flux is enhanced up to 200%, and the thermal conductivity is increased up to from 10 to 160%. However, the fouling phenomenon can be occurred that nanoparticles of nanofluids are deposited on the heat transfer surface. Therefore, to investigate relation between nanofluid and fouling, this study is carried out using oxidized graphene nanofluid. Also it compared and analyzed the critical heat flux and the boiling heat transfer coefficient. As the result, in case of oxidized graphene deposition for fouling, the critical heat flux is increased up to 20% more than oxdized graphene nanofluid. However, the boiling heat transfer coefficient is decreased down to about $6kW/m^2K$ at $1,000kW/m^2$ more than pure water.

Development of Optimal Thermal Transfer Calculation Algorithm by Composition of Thermal Transfer Mechanism among Integrated Energy Operators (집단에너지 사업자간의 열연계 메커니즘 구성에 의한 최적 열연계 산정 알고리즘 개발)

  • Kim, Yongha;Kim, Seunghee;Hyeon, Seungyeon
    • Journal of Energy Engineering
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    • v.26 no.4
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    • pp.57-66
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    • 2017
  • Since the heat is not as fast as the electric power and the loss is relatively large compared to the electric power, it is not realistic to operate the thermal transfer system with on operation center like electric power trading. In the case of the Korea District Heating Corporation, where all the thermal transfer are currently being made, only two or four adjacent heat-generating power plants are being the heat trading. Therefore, In this paper, we concluded that it is appropriate to divide the integrated operation center for heat trading into several regions, to operate the hub integrated operation power plant in each region to reflect the characteristics of the heat medium and proposed the thermal transfer mechanism among integrated energy operators. Then, we have developed an algorithm that can optimize the heat transaction for the proposed mechanism and applied it to the actual operators to verify the usefulness of the proposed algorithm.

Effect of Radiation Heat Transfer on the Control of Temperature Gradient in the Induction Heating Furnace for Growing Single Crystals (전자기 유도가열식 단결정 성장로의 온도 구배제어에 있어 복사열 전달의 효과)

  • Park, Tae-Yong;Shin, Yun-Ji;Ha, Minh-Tan;Bae, Si-Young;Lim, Young-Soo;Jeong, Seong-Min
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.32 no.6
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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.

Ab initio SCF Calculations of Potential Energy Surfaces for the Proton Transfer in a Formamide Dimer

  • Kong, Young-Shik;Jhon, Mu-Shik
    • Bulletin of the Korean Chemical Society
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    • v.12 no.1
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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.

Dynamic Analysis of a Three-Axis Mechanism for Transfer Robots (3축 이송용 로봇의 동적 해석)

  • Lee, Suk Young
    • Journal of Energy Engineering
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    • v.24 no.3
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    • pp.128-134
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    • 2015
  • This research is that analyze multi-body system that have flexible and rigid body. Transfer robots are widely used mainly in automobile industry owing to its capability to handle heavy parts with high speed in wide range of movement. For the transfer robots to widen the application area, a new three-axis mechanism with heavy payload has been recently developed in consideration of the strength and stiffness. For the purpose, transient dynamic analysis is carried out to find the component position yielding a certain time. Though this research, we can analysis stress distribution and deformation of robot component.

A Study on Charateristic of Modern Packing, 25mm NSW-ring, ppm by Absorption of NH3 gas (25mm NSW-ring, pp.를 충진한 충진탑에서 암모니아 흡수에 의한 유해가스 처리시 충진물의 특성연구)

  • 신은재;박진식
    • Journal of Environmental Science International
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    • v.6 no.4
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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.

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Estimation of Output Voltage and Magnetic Flux Density for a Wireless Charging System with Different Magnetic Core Properties

  • Park, Ji Hea;Kim, Sang Woo
    • Journal of Magnetics
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    • v.18 no.2
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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.

The Effect of Operating Conditions on the Frost Formation in a Vertical Plate at a Low Temperature (저온 수직평판에서 착상에 대한 운전조건의 영향)

  • 이관수;이태희;김우승
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.12
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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.

Heat Transfer in a Horizontal Mantle Heat Exchanger for a Thermosyphon-driven Flat Plate Collector (자연대류형 태양열 온수기용 맨틀 축열조의 열전달 현상에 관한 연구)

  • Cho, H.J.;Seo, T.B.;Kang, Y.H.
    • Journal of the Korean Solar Energy Society
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    • v.21 no.3
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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.

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Energy Transfer between Calixarene and Naphthalene

  • Kook, Seong-Keun
    • Bulletin of the Korean Chemical Society
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    • v.23 no.8
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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.