• Title/Summary/Keyword: gas transfer

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Decarbonization Kinetics of Molten Iron by Ar+O2 Gas Bubbling (Ar+O2 혼합가스 취입에 의한 용철의 탈탄 반응속도)

  • Sohn, Ho-Sang;Jung, Kwang-Hyun
    • Korean Journal of Metals and Materials
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    • v.47 no.2
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    • pp.107-113
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    • 2009
  • Molten iron with 2 mass % carbon content was decarbonized at 1823 K~1923 K by bubbling $Ar+O_2$ gas through a submerged nozzle. The reaction rate was significantly influenced by the oxygen partial pressure and the gas flow rate. Little evolution of CO gas was observed in the initial 5 seconds of the oxidation; however, this was followed by a period of high evolution rate of CO gas. The partial pressure of CO gas decreased with further progress of the decarbonization. The overall reaction is decomposed to two elementary reactions: the decarbonization and the dissolution rate of oxygen. The assumptions were made that these reactions are at equilibrium and that the reaction rates are controlled by mass transfer rates within and around the gas bubble. The time variations of carbon and oxygen contents in the melt and the CO partial pressure in the off-gas under various bubbling conditions were well explained by the mathematical model. Based on the present model, it was explained that the decarbonization rate of molten iron was controlled by gas-phase mass transfer at the first stage of reaction, but the rate controlling step was transferred to liquid-phase mass transfer from one third of reaction time.

Evaluation of Operating Conditions for the Natural Gas Transmission Pipeline in the Arctic Environment (극한지 장거리 천연가스 배관의 운전조건 평가)

  • Kim, Young-Pyo;Kim, Ho-Yeon;Kim, Woo-Sik
    • Journal of the Korean Institute of Gas
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    • v.21 no.1
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    • pp.72-79
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    • 2017
  • The operating temperature range of the natural gas pipeline in Arctic environment would be controlled primarily to optimize gas throughput and to minimize the environmental impact resulting from operation of such pipelines. The temperature of the gas as it flows through the pipeline is a function of both the Joule-Thomson effect and the pipe to soil heat transfer. Therefore, the heat transfer and Joule-Thomson effect of the buried natural gas pipeline in this study were carefully considered. Soil temperatures and overall heat transfer coefficients were assumed to be $0{\sim}-20^{\circ}C$ and $0{\sim}5.5W/m^2K$, respectively. The gas temperature and pressure calculations along a pipeline were performed simultaneously at different soil temperatures and overall heat transfer coefficients. Also, this study predicted the phase change and hydrate formation for different soil temperatures and overall heat transfer coefficients using HYSYS simulation package.

Measurement of Heat Transfer and Pressure Distributions on a Gas Turbine Vane Endwall (가스터빈 베인 끝벽의 열전달 특성 및 정압분포 측정)

  • Lee, Yong-Jin;Shin, So-Min;Kwak, Jae-Su
    • Journal of the Korean Society for Aviation and Aeronautics
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    • v.14 no.2
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    • pp.33-38
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    • 2006
  • Heat transfer coefficients and static pressure distributions on a gas turbine vane endwall were experimentally investigated in a 5 bladed linear cascade. The Reynolds number based on an axial chord length and the cascade exit velocity was 500,000. Both heat transfer and pressure measurements on the vane endwall were made at the two different turbulence intensity levels of 6.8% and 10.8%. Detailed heat transfer coefficient distributions on the vane endwall region were measured using a hue detection based transient liquid crystals technique. Results show various regions of high and low heat transfer coefficients on the vane endwall surface due to several types of secondary flows and vortices. Heat transfer coefficient and endwall static pressure distributions showed similar trends for both turbulence intensity, however, the averaged heat transfer coefficients for higher turbulence intensity case was higher than the lower turbulence intensity case by 15%.

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GMA Torch Configuration for Efficient Use of Argon Gas Part 2 : Comparison between AMAG DMAG Process (아르곤 가스를 효율적으로 사용하기 위한 GMA 용접 토치 구조 Part 2 : AMAG와 DMAG 공정의 비교)

  • 문명철;고성훈;유중돈
    • Journal of Welding and Joining
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    • v.17 no.6
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    • pp.46-52
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    • 1999
  • The auxiliary gas-shielded MAG (AMAG) process, which was devised to provide an argon-rich shielding environment using small amount of argon gas, was investigated experimentally to figure out its effects on metal transfer and weld quality. Proper conditions for the AMAG process including the argon gas ratio, position and direction of the auxiliary nozzle were determined experimentally. Performance of the AMAG process was compared with that of the double gas-shielded MAG(DMAG) and MAG processes by monitoring the bead profile, current and voltage waveforms. The AMAG process was found to provide better bead profile, more stable arc and wider operating range of spray transfer mode compared with the DMAG process. In general, performance of the AMAG process using the argon ratio of 30% was comparable to that of the MAG process using 80% argon and 20% CO₂ gas.

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Heat Transfer Analysis of a Coil-Typed LPG Vaporizer with an Electrically Heating Water Bath (전열온수식 LPG 기화기의 열전달 해석)

  • Choi, Sung-Joon;Kwon, Jeong-Rock;Kim, Kwang-Seok;Kim, Hyo
    • Journal of the Korean Institute of Gas
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    • v.11 no.3
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    • pp.19-25
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    • 2007
  • The heat transfer phenomena in a coil-typed LPG vaporizer with a hot water bath employed an electrical heating system were experimentally analyzed. The heat energy is initially used to sensible heat region to heat LPG and then is done to latent heat region to vaporize LPG and to heat up the vaporized gas. A two-phase flow region could be found from periodic temperature fluctuations, and only sensible heat effect was found after passing through the region. The overall heat capacity was defined as multiplying the overall heat transfer coefficient by the heat transfer area and we found a correlation employing the heating water temperature and LPG flow rate. The results of this work can effectively be applied for the design of field scale LPG vaporizers in the near future because they can predict the features of heat transfer on a kind of coil type LPG vaporizer.

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Mass Transfer of Gas-Liquid in Agitated Vessel Using Wire Gauge Impeller (금망임펠러를 이용한 교반조에서의 기-액 물질이동)

  • Lee, Young-Sei
    • Journal of the Korean Society of Industry Convergence
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    • v.11 no.1
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    • pp.19-26
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    • 2008
  • The gas-liquid mass transfer volumetric coefficients in gas-liquid agitated vessels with wire gauge impellers were measured to be compared with those in vessels with disk turbine and paddle impellers. Also mass transfer volumetric coefficients for disk turbine, paddle impeller and wire gauge impeller in cylindrical agitated vessel was measured over a wide range of Reynolds number from turbulent flow to transition regions. The effect of geometries on $k_La$ is clarified experimentally. Mass transfer volumetric coefficients $k_La$ depends only on the power consumption ($P_{gv}+P_{av}$) per unit volume.

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Numerical Investigation of Flow and Heat Transfer Characteristics on the Gas Turbine Blade with a Squealer Tip (스퀼러팁을 이용한 가스터빈 내에서의 3차원 유동 및 열전달 특성에 관한 연구)

  • Jung, Jong-Hun;Moon, Young-J.;Kim, Jin-Young
    • 한국전산유체공학회:학술대회논문집
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    • 2008.03b
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    • pp.159-162
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    • 2008
  • In this paper, a numerical simulation of three-dimensional flow field and heat transfer coefficient distribution are conducted for two types of gas turbine blade with plane and squealer tips. The numerical results show that gas turbine blade with squealer tip considerably changes the flow structures near the tip regions of pressure and suction sides, so the overall heat transfer coefficients on the tip and shroud with squealer tip are lower than those with the plane tip blade. Finally, the effect of tip gap clearance on the flow field and heat transfer characteristics are investigated.

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Heat Transfer and Pressure Drop of $CO_2$ Gas Cooler in a Helically Coiled Tube (헬리컬코일형 $CO_2$ 가스쿨러의 열전달과 압력강하)

  • Kyoung, Nam-Soo;Yu, Tae-Guen;Son, Chan-Hyo;Oh, Hoo-Kyu
    • Proceedings of the Korean Society of Marine Engineers Conference
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    • 2005.11a
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    • pp.246-247
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    • 2005
  • The paper presents the heat transfer characteristics during cooling process of carbon dioxide($CO_2$) in a helically coiled tube. The main components of the apparatus consist of a receiver, a variable speed pump, a mass flowmeter, a pre-heater, a gas cooler(test section) and an isothermal tank. The test section with the inner diameter 4.55 [mm] is a tube in tube type heat exchanger with refrigerant flowing in the inner tube and water flowing in the annulus. The main results were summarized as follows : The heat transfer coefficient increases with respect to the decrease of the gas cooler pressure in a supercritical region and the increase of the refrigerant mass flux. The pressure drop decreases in increases of the gas cooler pressure and increases with respect to increases the refrigerant mass flux.

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A Combustion Instability Analysis of a Model Gas Turbine Combustor by the Transfer Matrix Method

  • Cha, Dong-Jin;Kim, Jay-H.;Joo, Yong-Jin
    • Proceedings of the KSME Conference
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    • 2008.11b
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    • pp.2946-2951
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    • 2008
  • Combustion instability is a major issue in design of gas turbine combustors for efficient operation with low emissions. Combustion instability is induced by the interaction of the unsteady heat release of the combustion process and the change in the acoustic pressure in the combustion chamber. In an effort to develop a technique to predict self-excited combustion instability of gas turbine combustors, a new stability analysis method based on the transfer matrix method is developed. The method views the combustion system as a one-dimensional acoustic system with a side branch and describes the heat source as the input to the system. This approach makes it possible to use the advantages of not only the transfer matrix method but also well-established classic control theories. The approach is applied to a simple gas turbine combustion system to demonstrate the validity and effectiveness of the approach.

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Two-phase flow and heat transfer characteristics in a submerged gas injection system (잠겨진 가스분사장치에서의 2상 유동 및 열전달 특성)

  • 최청렬;김창녕
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.11 no.6
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    • pp.824-834
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    • 1999
  • Characteristics of two-phase flow and heat transfer were numerically investigated in a submerged gas injection system when temperature of the injected gas was different from that of the liquid. The Eulerian approach was used for both the continuous and dispersed phases. The turbulence in the liquid phase was modeled using the standard $k-\varepsilon$$\varepsilon$ turbulence model. The interphase friction and heat transfer coefficient were calculated from the correlations available in the literature. The turbulent dispersion of the phases was modeled by a "dispersion Prandtl number". In the case with heat transfer where the temperature of the injected gas is higher than the mean liquid temperature, the axial and the radial velocities are lower in comparison with the case of homogeneous temperatures. The results in the present research are of interest in the design and operation of a wide variety of material and chemical processes.

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