• 제목/요약/키워드: Gas-phase Analysis

검색결과 878건 처리시간 0.027초

기액이상류의 압력손실과 가스상의 체적분율에 관한 이론적 해석 (A Theoretical Analysis on Pressure Loss and Gas Volumetric Fraction of Gas-Liquid Two-Phase Flow)

  • 최부홍
    • 해양환경안전학회지
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    • 제15권1호
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    • pp.63-69
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    • 2009
  • 가스상의 체적분율과 압력강하는 기액이상류에 대한 이해와 예측에 있어서 매우 중요한 인자이다. 또한 그것들은 산업용 대용량의 열교환시스템 및 선박에 설치되는 보일러 및 냉동시스템의 설계에 있어서 필수적인 항목이다. 따라서 본 논문에서는 파이프의 모든 경사각도에서 기액이상류 가스상의 체적분율과 압력손실을 예측할 수 있는 이론적 해석 방법을 제시한다. 여기서의 이론적 해석은 2유체 층상류 모델을 기초로 하고 있다. 또한 이론적 해석결과와 기존의 실험결과와 비교한 결과에 대해서도 제시한다.

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A Study on the Mixture Formation Process of Diesel Fuel Spray in Unsteady and Evaporative Field

  • Yeom, Jeong-Kuk;Park, Jong-Sang;Chung, Sung-Sik
    • Journal of Mechanical Science and Technology
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    • 제19권12호
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    • pp.2253-2262
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    • 2005
  • The focus of this work is placed on the analysis of the mixture formation mechanism under the evaporative diesel spray of impinging and free conditions. As an experimental parameter, ambient gas density was selected. Effects of density variation of ambient gas on liquid and vapor-phase inside structure of evaporation diesel spray were investigated. Ambient gas density was changed between ${\rho}a=5.0\;kg/m^3$ and $12.3\;kg/m^3$. In the case of impinging spray, the spray spreading to the radial direction is larger due to the decrease of drag force of ambient gas in the case of the low density than that of the high density. On the other hand, in the case of free spray, in accordance with the increase in the ambient gas density, the liquid-phase length is getting short due to the increase in drag force of ambient gas. In order to examine the homogeneity of mixture consisted of vapor-phase fuel and ambient gas in the spray, image analysis was conducted with statistical thermodynamics based on the non-dimensional entropy (S) method. In the case of application of entropy analysis to diesel spray, the entropy value always increases. The entropy of higher ambient density is higher than that of lower ambient gas density during initial injection period.

복사효과를 고려한 기체-입자 직접접촉식 열교환기 해석 (Analysis of a gas-particle direct-contact heat exchanger with two-phase radiation effect)

  • 박재현;백승욱;권세진
    • 대한기계학회논문집B
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    • 제22권4호
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    • pp.542-550
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    • 1998
  • A direct contact heat exchanger using particle-suspended gas as a heat transfer medium is analyzed with an extended emphasis on the radiation, i. e., considering the radiation by both gas and particles. While the Runge-Kutta method is used for a numerical analysis of the momentum and energy equations, the finite volume method is utilized to solve the radiative transfer equation. Present study shows a notable effect by the gas radiation in addition to the particle radiation, especially when changing the chamber length as well as the gas and particle mass flow rate. When the gas and particle mass flow rate is raised, the gas temperature in the particle heater still increases as the gas absorption coefficient increases, which is different from the results for the small scale heat exchanger.

서울 대기 중 기체 및 입자상 다환방향족탄화수소 (PAHs)의 낮·밤 분포 특성 (Day and Night Distribution of Gas and Particle Phases Polycyclic Aromatic Hydrocarbons (PAHs) Concentrations in the Atmosphere of Seoul)

  • 임형배;김용표;이지이
    • 한국대기환경학회지
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    • 제32권4호
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    • pp.408-421
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    • 2016
  • Day and night sampling for gas and particle phases PAHs were carried out in Seoul to characterize gas and particle phases PAHs concentrations in day and night times. There was no significant difference between day and night time for particle phase PAHs concentrations and phase distribution of PAHs, while, gas phase PAHs concentrations in daytime were about 1/2 of nighttime concentrations in both summer and winter due to photochemical reaction of gas phase PAHs during daytime. A high fraction of cancer risk for PAHs was attributed to particle phase PAHs and the excess cancer risk in winter was higher than in summer. The excess cancer risk level of total(gas+particle) PAHs in summer was partially observed when both gas and particle phase PAHs concentrations were considered as risk assessment. Based on the diagnostic ratios and factor analysis of PAHs concentrations, combustion(coal and natural gas) and vehicular emission might be the most significant contributors of PAHs and major factors for determining of PAHs concentration were different between day and night times.

Calculation of Temperature Rise in Gas Insulated Busbar by Coupled Magneto-Thermal-Fluid Analysis

  • Kim, Hong-Kyu;Oh, Yeon-Ho;Lee, Se-Hee
    • Journal of Electrical Engineering and Technology
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    • 제4권4호
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    • pp.510-514
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    • 2009
  • This paper presents the coupled analysis method to calculate the temperature rise in a gas insulated busbar (GIB). Harmonic eddy current analysis is carried out and the power losses are calculated in the conductor and enclosure tank. Two methods are presented to analyze the temperature distribution in the conductor and tank. One is to solve the thermal conduction problem with the equivalent natural convection coefficient and is applied to a single phase GIB. The other is to employ the computational fluid dynamics (CFD) tool which directly solves the thermal-fluid equations and is applied to a three-phase GIB. The accuracy of both methods is verified by the comparison of the measured and calculated temperature in a single phase and three-phase GIB.

GITr(Gas Insulated Transformer) 내부에 발생되는 PD 신호의 패턴분석을 위한 PRPD와 CAPD 적용결과 비교 (A Comparative Study of The PD Pattern Analysis Based on PRPD and CAPD for The Diagnosis of Gas Insulated Transformer)

  • 정승용;구자윤
    • 대한전기학회논문지:전기물성ㆍ응용부문C
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    • 제55권6호
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    • pp.308-312
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    • 2006
  • Partial Discharge (PD) phenomena occurred by different nature of insulating defects has been regarded as a random process by which Phase Resolved Partial Discharge Analysis(PRPDA) has been proposed and then commercially accepted for the diagnosis of the power apparatus since more than three decades. Moreover, for the same purpose, a novel approach based on the Chaotic Analysis(CAPD) has been proposed since 2000, in which Partial Discharge(PD) phenomena is suggested to be considered as a deterministic dynamical process. In this work, for the diagnosis of Gas Insulated Transformer(GITr), four different types of specimen were fabricated as a model of the possible defects that might possibly cause its sudden failures such as turn to turn insulation, inter coil insulation, free moving particle and protrusion. For this purpose, these defects are introduced into the Gas Insulated Transformer(GITr) mock-up and experimental investigations have been carried out in order to analyze the related Partial Discharge(PD) patterns by means of both Phase Resolved Partial Discharge Analysis(PRPDA) and Chaotic Analysis(CAPD) respectively and then their comparisons are made systematically.

다상 유동 해석을 위한 압축성 실제기체 해법 (A REAL GAS SOLUTION ALGORITHMS FOR MULTI-PHASE FLOW ANALYSIS)

  • 한상훈;최정열
    • 한국전산유체공학회:학술대회논문집
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    • 한국전산유체공학회 2005년도 추계 학술대회논문집
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    • pp.187-194
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    • 2005
  • For the analysis of compressible multi-phase and real gas flows, characteristic form of Roe's Riemann solver was derived using real gas equation of state. It was extended to multi component reactive system considering variable specific heat. From this study, it is known that some correction should be made for the use of existing numerical algorithm. 1) Sonic speed and characteristic variable should be corrected with real gas effect. 2) Roe's average was applicable only with the assumption of constant properties. 3) Artificial damping term and characteristic variables should be corrected but their influences may not be significant.

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Review on Gas-Voiding Models for HCDA(Hypothetical Core Disruptive Accident) Initiating Phase in LMR Analysis (I)

  • Chang, W.P.;Kwon, Y.M.;Hahn, D.H.;Suk, S.D.
    • Nuclear Engineering and Technology
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    • 제31권6호
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    • pp.51-65
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    • 1999
  • The present review report introduces the existing analysis codes and physical modeling of two-phase flow associated with initiating event of HCDA in Liquid Metal Reactors for the effective study in the future, because the related research has not been systematically carried out in Korea compared with other areas. The description in this report is specifically addressed to the results yielded from careful review of the technical concepts on the two-phase flow modeling in the SAS2A code which was developed in ANL. The report is prepared in 2 parts based on the definite physical phenomena. The liquid slug and gas behavior models are main representations in the part (I) and (II), respectively. In this regard, it is expected that this report provide a fundamental knowledge on the two-phase flow model in LMR and, thus, contribute to establishment of the necessary HCDA analysis technology concerned with the LMR development in Korea.

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Application of Preconditioning Method to Cavitating Flow Computation

  • Shin, Byeong-Rog
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2004년도 춘계학술대회
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    • pp.1903-1908
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    • 2004
  • A preconditioned numerical method for gas-liquid two-phase flows is applied to solve cavitating flow. The present method employs a finite-difference dual time-stepping integration procedure and the MUSCLTVD scheme. A homogeneous equilibrium cavitation model is used. The present density-based numerical method permits simple treatment of the whole gas-liquid two-phase flow field, including wave propagation, large density changes and incompressible flow characteristics at low Mach number. Some internal flows such as convergent-divergent nozzles are computed using this method. Comparisons of predicted and experimental results are provided and discussed.

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