• 제목/요약/키워드: Heat Generation

검색결과 1,805건 처리시간 0.022초

액화천연가스 냉열을 이용한 단일팽창과 이단팽창 사이의 비교 연구 (Comparative Study between Single-stage and Two-stage Expansion Using LNG Cold Heat)

  • 노상균
    • 한국수소및신에너지학회논문집
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    • 제30권2호
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    • pp.188-192
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    • 2019
  • Comparative studies between single- and two-stage expansion process using LNG cold heat have been performed for a closed Rankine power generation cycle. PRO/II with PROVISION release 10.0 from Schneider Electric Company was used, and the Peng-Robinson equation of state model with Twu's alpha function was selected for the modeling and optimization of the power generation cycle using LNG cold heat. In two-stage power generation cycle, 6.7% more power was obtained compared to that of single-stage power generation cycle through the optimization works.

공기저어널 베어링에서 저어널의 고속회전시 공기유막내의 열발생에 관한 연구 (A study on the heat generation into air film as rotating of high speed journal in the air journal bearing)

  • 이종열;성승학;이득우;박보선;김태영
    • 한국공작기계학회:학술대회논문집
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    • 한국공작기계학회 2002년도 춘계학술대회 논문집
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    • pp.82-86
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    • 2002
  • The thermal characteristics of high-speed air spindle system with built-in motor are studied. Experiment and finite difference method analysis obtain temperature rise and temperature distribution of housing. For the analysis, air fluid film model is built and temperature rise and distribution in thermal steady state are computed for each rotational speed. Generally, it is said that the heat generation of air bearing is negligible. But the heat generation in air film by heat dissipation can not be negligible especially into high-speed region of the journal. In case that the heat generation of air spindle system is high, natural frequency of the spindle system becomes lower when the thermal state is in steady-state and it means the changes of air bearing stiffness due to the change of bearing clearance. It is shown that the temperature rise of air spindle system causes thermal expansion and induces the variation of bearing clearance. In consequence the stiffness of air bearing becomes smaller.

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Heat Generation of Angular Contact Ball Bearings

  • Rhim, Yoon-Chul;Na, Hee-Hyeong
    • Tribology and Lubricants
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    • 제11권5호
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    • pp.122-127
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    • 1995
  • The heat generations of angular contact ball bearings are studied experimentally with numerical simulations. The temperature variations of inner and outer races and the temperature increase distributions are measured by using thermocouples for the spindle rotational speeds, preloads, viscosity of oils, and lubrication methods. The measured values from experiments are used to estimate the heat generation rates. The heat generation is focused mainly on the dominant sources which are robbings due to spin and gyro-moments of bearing balls, applied load and viscous friction. Oil-jet and oil-air lubrication methods are adopted using oils with different viscosities.

MHD발전용 작동 플라즈마를 고온가열하기 위한 효율적 방안에 관한 연구 (Studies on a Effective Scheme to Obtain High Temperature Working Plasma for MHD Power Generation)

  • 김윤식;노창주;김영길;공영경;최춘성
    • 대한기계학회논문집
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    • 제17권1호
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    • pp.153-161
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    • 1993
  • 본 연구에서는 각 운전모드별 열특성을 전체적으로 고려하여 양질의 MHD발전 용 작동플라즈마를 얻기 위하여 필요한 효과적인 방책에 관하여 집중적으로 고찰하고 자 한다.

히트펌프를 이용한 PEMFC 기반 열병합 발전 시스템 (PEMFC Based Cogeneration System Using Heat Pump)

  • 뚜안앵;김영상;이동근;안국영
    • 한국수소및신에너지학회논문집
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    • 제32권5호
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    • pp.324-330
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    • 2021
  • In recent years, polymer electrolyte membrane fuel cell (PEMFC) based cogeneration system has received more and more attention from energy researchers because beside electricity, the system also meets the residential thermal demand. However, the low-quality heat exited from PEMFC should be increased temperature before direct use or storage. This study proposes a method to utilize the heat exhausted from a 10 kW PEMFC by coupling a heat pump. Two different configuration using heat pump and a reference layout with heater are analyzed in term of thermal and total efficiency. The system coefficient of performance (COP) increases from 0.87 in layout with heaters to 1.26 and 1.29 in configuration with heat pump and cascade heat pump, respectively. Lastly, based on system performance result, another study in economics point of view is proposed.

발열 전도체를 가지는 밀폐계 내부의 자연대류 현상에 대한 수치적 연구 (Numerical Study of Thermal Convection in Horizontal Enclosure with Heat Generating Conducting Body)

  • 이재룡;하만영
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2004년도 추계학술대회
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    • pp.1080-1085
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    • 2004
  • The physical model considered here is a horizontal layer of fluid heated below and cold above with heat-generating conducting body placed at the center of the layer. The dimensionless thermal conductivities of body considered in the present study are 0.01, 1 and 150. The dimensionless temperature difference ratios considered are 0.25, 2.5 and 25. Two-dimensional solution for unsteady natural convection is obtained using an accurate and efficient Chebyshev spectral methodology for variety of Rayleigh number from $10^{3}$ to $10^{6}$. Multi-domain technique is used to handle square-shaped heat-generating conducting body. The results for the case of conducting body with heat generation are also compared to those without heat generation.

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온도측정에 의한 히트파이프의 수명예측 (Prediction of Life of Heat Pipes by Measuring Temperature Distribution)

  • 신흥태;;이윤표
    • 대한기계학회논문집B
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    • 제23권7호
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    • pp.856-863
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    • 1999
  • The thermal performance degradation of heat pipes is caused by the non-condensable gas generation mainly due to the electrochemical corrosion which results from the reaction of working fluids with tube materials. In this study, a simplified method described below was proposed to estimate the life of heat pipes concerning the non-condensable gas generation. The temperature distributions at the outer surface of heat pipes was measured, and based on them the amount of non-condensable gas of hydrogen was estimated. Applying it to the Arrhenius model, the mass generation of hydrogen and the volume occupied by the gas In heat pipes could be estimated for an operating temperature and time. Moreover, this simplified method was applied to the accelerated life test of nine methanol-stainless steel heat pipe samples.

발열 전도체가 존재하는 밀폐계 내부의 자연대류 현상에 대한 수치적 연구 (Numerical Simulation of Natural Convection in Horizontal Enclosure with Heat-Generating Conducting Body)

  • 이재룡;하만영
    • 대한기계학회논문집B
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    • 제29권4호
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    • pp.441-452
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    • 2005
  • The physical model considered here is a horizontal layer of fluid heated below and cold above with heat-generating conducting body placed at the center of the layer. The dimensionless thermal conductivities of body considered in the present study are 0.01, 1 and 150. The dimensionless temperature difference ratios considered are 0.25, 2.5 and 25. Two-dimensional solution for unsteady natural convection is obtained using an accurate and efficient Chebyshev spectral methodology for variety of Rayleigh number from $10^{3}\;to\;10^{6}.$ Multi-domain technique is used to handle square- shaped heat-generating conducting body. The results for the case of conducting body with heat generation are also compared to those without heat generation.

산화철 나노 입자의 발열 효과의 제어 (Controlling the Heat Generation Capability of Iron Oxide-Base Nanoparticles)

  • 최진실
    • 한국분말재료학회지
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    • 제28권6호
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    • pp.518-526
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    • 2021
  • This review summarizes the recent progress in iron-oxide-based heat generators. Cancer treatment using magnetic nanoparticles as a heat generator, termed magnetic fluid hyperthermia, is a promising noninvasive approach that has gained significant interest. Most previous studies on improving the hyperthermia effect have focused on the construction of dopant-containing iron oxides. However, their applications in a clinical application can be limited due to extra dopants, and pure iron oxide is the only inorganic material approved by the Food and Drug Administration (FDA). Several factors that influence the heat generation capability of iron-oxide-based nanoparticles are summarized by reviewing recent studies on hyperthermia agents. Thus, our paper will provide the guideline for developing pure iron oxide-based heat generators with high heat dissipation capabilities.

Second law thermodynamic analysis of nanofluid turbulent flow in heat exchanger

  • K. Manjunath
    • Advances in Energy Research
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    • 제8권3호
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    • pp.125-136
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    • 2022
  • Entropy generation along with exergetic analysis is carried out using turbulent nanofluid flow in the heat exchanger. To obtain the optimized percentage constituent of nanofluid, the nanofluid volume concentrations is varied for the given input conditions. For different Reynolds number of the fluid and heat capacity rate ratio between the streams, the heat transfer improvements are studied in terms of nano particles diameter. Parametric analysis is carried out for a counterflow heat exchanger using turbulent nanofluid flow with exergetic efficiency along with entropy generation number as performance parameters. The exergetic efficiency provides realistic approach in the design of nanofluid applications in heat exchanger leading to conservation of energy.