• 제목/요약/키워드: Heat Balance

검색결과 657건 처리시간 0.031초

$C_2H_4$/Air 비예혼합 난류화염의 매연생성 모델링 (Numerical Modeling of Soot Formation in $C_2H_4$/Air Turbulent Non-premixed Flames)

  • 김태훈;우민호;김용모
    • 한국연소학회지
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    • 제15권4호
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    • pp.22-28
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    • 2010
  • The Direct Quadrature Method of Moments (DQMOM) has been presented for the solution of population balance equation in the wide range of the multi-phase flows. This method has the inherently interesting features which can be easily applied to the multi-inner variable equation. In addition, DQMOM is capable of easily coupling the gas phase with the discrete phases while it requires the relatively low computational cost. Soot inception, subsequent aggregation, surface growth and oxidation are described through a population balance model solved with the DQMOM for soot formation. This approach is also able to represent the evolution of the soot particle size distribution. The turbulence-chemistry interaction is represented by the laminar flamelet model together with the presumed PDF approach and the spherical harmonic P-1 approximation is adopted to account for the radiative heat transfer.

틸팅패드 스러스트베어링의 모멘트평형에 대한 고찰 (On Moment Balance of Tilting-Pad Thrust Bearings)

  • 김호종;최성필;하현천
    • 한국윤활학회:학술대회논문집
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    • 한국윤활학회 2003년도 학술대회지
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    • pp.261-266
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    • 2003
  • The present paper theoretically investigates characteristics of moment balance of a tilting-pad thrust bearing. Pressure of lubricant film of the bearing was computed using tile finite element method, and average film temperature was estimated from the heat balance over a pad. From the investigation, it has been found that different two sets of tilt angles satisfy moment equilibrium of the pad about tile pivot for a given pivot location. The tilt angles converged depend upon initial tilt angles assumed. Quite different bearing performance, including load capacity, film thickness, and temperature, is shown to be obtained based on choice of the initial tilt angles.

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폐주물사의 용융공정에서의 물질 및 에너지 수지의 해석 (Analysis of Energy and Material Balance in Smelting Process of Waste Sand)

  • 정원섭;민동준;윤수종
    • 한국주조공학회지
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    • 제15권5호
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    • pp.477-482
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    • 1995
  • A computer simulation model of various smelting process for melting waste sand was developed by using energy and material balance concept. This model can predict the coal, flux and oxygen consumption and the volume and temperature of off-gas. The major critical variables for smelting process can be explained by using the analysis of energy and material balance. The major conclusions were as follows; 1. The most important variables for smelting process were high post-combustion ratio, high heat transfer efficiency and refractory protection technology. 2. For saving energy in this smelting process, selection of raw materials i.e coal, flux are very important, espacially using of low volatile coal is very profitable. 3. The treatment cost of waste sand is high and environmental restriction is severe, in this reason we must be concerned in the treatment of waste sand by smelting process.

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틸팅패드 스러스트베어링의 모멘트평형에 대한 고찰 (On Moment Balance of Tilting-Pad Thrust Bearings)

  • 김호종;최성필;하현천
    • Tribology and Lubricants
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    • 제20권3호
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    • pp.152-156
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    • 2004
  • The present paper theoretically investigates characteristics of moment balance of a tilting-pad thrust bearing. Pressure of lubricant film of the bearing was computed using the finite element method, and average film temperature was estimated from the heat balance over a pad. From the investigation, it has been found that different two sets of tilt angles satisfy moment equilibrium of the pad about the pivot for a given pivot location. The tilt angles converged depend upon initial tilt angles assumed. Quite different bearing performance, including load capacity, film thickness, and temperature, is shown to be obtained based on choice of the initial tilt angles.

토양 및 지하수 조건이 지열공조시스템의 성능에 미치는 영향에 관한 수치 해석적 연구 (Numerical Analysis for the Effect of Ground and Groundwater Conditions on the Performance of Ground Source Heat Pump Systems)

  • 남유진
    • 설비공학논문집
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    • 제23권5호
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    • pp.321-326
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    • 2011
  • Recently, ground source heat pump (GSHP) systems have been introduced in many modem buildings which use the annually stable characteristic of underground temperature as one of the renewable energy uses. However, all of GSHP systems cannot achieve high level of energy efficiency and energy-saving, because their performance significantly depends on thermal properties of soil, the condition of groundwater, building loads, etc. In this research, the effect of thermal properties of soil on the performance of GSHP systems has been estimated by a numerical simulation which is coupled with ground heat and water transfer model, ground heat exchanger model and surface heat balance model. The thermal conductivity of soil, the type of soil and the velocity of groundwater flow were used as the calculation parameter in the simulation. A numerical model with a ground heat exchanger was used in the calculation and, their effect on the system performance was estimated through the sensitivity analysis with the developed simulation tool. In the result of simulation, it founds that the faster groundwater flow and the higher heat conductivity the ground has, the more heat exchange rate the system in the site can achieve.

수평원관 내 이산화탄소의 증발열전달 특성 연구 (A Study on the Characteristics of Evaporative Heat Transfer for Carbon Dioxide in a Horizontal Tube)

  • 조은석;윤석호;김민수
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2000년도 춘계학술대회논문집B
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    • pp.104-107
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    • 2000
  • Evaporative heat transfer characteristics of carbon dioxide has been investigated. Experiment has been carried out for seamless stainless steel tube with outer diameter of 9.55 mm and inner diameter of 7.75 mm. Direct heating method is used for supplying heat to the refrigerant was uniformly heated by electric current which was applied to the tube wall. The saturation temperature of refrigerant is calculated from the measured saturation pressure by using an equation of state. Inner wall temperature was calculated from measured outer wall temperature, accounting for heat generation in the tube and heat conduction through the tube wall. Mass Quality of refrigerant was calculated by considering energy balance in the preheater and the test section. Heat fluxes were set at 12, 16, 20, 23, and $27kW/m^2$, mass fluxes were controlled at 212, 318, 424, and $530 kg/m^2s$, and saturation temperature of refrigerant were adjusted at 0, 3.4, 6.7 and $10.5^{\circ}C$. From this study, heat transfer coefficients of carbon dioxide have been provided with respect to quality for several mass fluxes, heat fluxes. Finally, the experimental results in this study are compared with the correaltion by Gungor and Winterton(1987).

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PEMFC 시스템 효율 향상을 위한 열 관리 설비 개발 및 연구 (Development and Research of Thermal Management Equipment for Efficiency Enhancement of PEMFC Systems)

  • 김재환;이지승;강인석;주현철
    • 한국수소및신에너지학회논문집
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    • 제35권2호
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    • pp.205-215
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    • 2024
  • This study introduced a direct contact heat exchanger to enhance the efficiency of polymer electrolyte membrane fuel cells (PEMFCs) systems. According to previous research, 28% of the operating costs of fuel cell systems are attributed to heat exchanger devices, prompting the design of a direct contact heat exchanger to address this issue. Optimal configurations were determined through computational fluid dynamics analysis and experimental device fabrication, and the enhanced heat exchange performance of the heat exchanger was experimentally confirmed. Through this, the contribution of the direct contact heat exchanger to the heat management and efficiency enhancement of PEMFC systems was established.

온실의 냉방부하 및 포그시스템의 증발효율 실험분석 (Empirical Analysis on the Cooling Load and Evaporation Efficiency of Fogging System in Greenhouses)

  • 남상운;서동욱;신현호
    • 생물환경조절학회지
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    • 제24권3호
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    • pp.147-152
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    • 2015
  • 온실의 냉방부하 산정방법 개발을 위하여 열수지 방법에 기초한 냉방부하 산정식을 구성하고, 포그냉방 온실에서 냉방부하를 실측하여 검증하였다. 포그냉방 온실의 냉각열량은 포그분사에 의한 증발수량에 물의 증발잠열을 곱하여 구할 수 있다. 여기서, 증발수량은 포그 분사량에 증발효율을 곱하면 구할 수 있으며, 즉 분무수량을 계측하고 포그시스템의 증발효율을 알면 온실의 냉방부하를 실측할 수 있다. 따라서 온실의 냉방부하 실측을 위하여 실험온실에서 포그시스템의 증발효율을 실험하고, 실험온실의 열환경 계측과 더불어 포그 분사량을 계측하여 냉방부하 산정방법을 검토하였다. 먼저 냉방부하 산정식의 환기전열량을 검토하기 위하여 냉방을 실시하지 않은 상태에서 환기량 실측 실험을 통해 비교한 결과 열수지식을 이용한 환기전열량 예측은 비교적 양호한 결과를 보이는 것으로 나타났다. 이류체 포그시스템의 증발효율은 0.3~0.94의 범위를 보였으며 평균 0.67로 나타났고, 환기율이 증가함에 따라 커지는 것으로 나타났다. 포그냉방을 실시하면서 온실의 환경을 계측하여 열수지식으로 냉방부하를 계산하고, 분무량 실측치로부터 증발 냉각열량을 구하여 비교한 결과 냉방부하 계산치와 실측치는 대체로 유사한 경향을 보이는 것으로 나타났다. 냉방부하가 낮은 경우에는 실측치에 비하여 약간 크게 예측되었고, 냉방부하가 높은 경우에는 실측치보다 작게 예측되었다. 온실의 냉방시스템 설계 시에는 최대냉방부하를 이용하여 냉방설비의 용량을 결정하게 된다. 따라서 냉방부하가 큰 쪽에서 실측치보다 작게 예측되는 부분은 검토가 필요하지만 설비용량 산정시의 안전계수를 고려하면 본 연구에서 제시한 냉방부하 산정방법은 온실의 환경설계에 적용할 수 있는 것으로 판단된다.

동적 에너지 시뮬레이션을 이용한 PCM보드의 설계변수 분석에 관한 연구 (Analysis of PCM Wallboards Design Parameters using Dynamic Energy Simulation)

  • 이진욱;안상민;김태연;이승복
    • KIEAE Journal
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    • 제12권4호
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    • pp.97-104
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    • 2012
  • A phase-change material is a substance with a high heat of fusion which, melting and freezing at a certain temperature, is capable of storing and releasing large amounts of energy. Heat is absorbed or released when the material changes from solid to liquid. Therefore, PCMs are classified as latent heat storage (LHS) units. The purpose of this study is to analyze PCM wallboard design parameters using dynamic energy simulation. Among the factors of PCM, melting temperature, latent heat, phase change range, thermal conductivity are very important element to maximize thermal energy storage. In order to analyze these factors, EnergyPlus which is building energy simulation provided by department of energy from the U.S is used. heat balance algorithm of energy simulation is conduction finite difference and enthalpy-temperature function is used for analyzing latent heat of PCM. The results show that in the case of melting temperature, the thermal energy storage could be improved when the melting temperature is equal to indoor surface temperature. It seems that when the phase change range is wide, PCM can store heat at a wide temperature, but the performance of heat storage is languished.

음장이 등온원통으로부터의 강제대류 열전달에 미치는 영향 (Effect of Sound Field on the Forced Convection Heat Transfer from an Isothermal Cylinder)

  • 권영필
    • 대한기계학회논문집
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    • 제12권2호
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    • pp.373-380
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    • 1988
  • 본 연구의 목적은 음장의 입자속도가 기류의 평균속도와 비슷한 크기인 경우에 원통으로부터 열전달의 동특성과 한 사이클의 평균값인 평균열전달이 음장에 의하여 어떠한 영향을 받는가를 구하기 위한 것이다.