• Title/Summary/Keyword: Water Exit Temperature

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Subscale high altitude simulation test using solid propellant gas generator (고체추진제 가스발생기를 이용한 축소형 고공환경모사 시험)

  • Kim, Yong-Wook;Lee, Jung-Ho;Yu, Byung-Il;Cho, Sang-Yeon;Oh, Seung-Hyub
    • Aerospace Engineering and Technology
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    • v.7 no.1
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    • pp.136-141
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    • 2008
  • Cylindrical supersonic exhaust diffuser, which utilizes the momentum of high temperature gas exhausted from nozzle, provides simple methods for obtaining stable and low pressure around the propulsion system. Hot zone on which exhausted gas from nozzle exit impinges directly should be cooled to avoid melting of diffuser. This paper describes method and result of subscale high altitude simulation test with water cooling. Subscale gas generator with solid propellant was used for hot gas source and tap water for coolant.

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Development of Simulation Model for Diffusion of Oil Spill in the Ocean 1 -Three Dimensional Characteristics of the Circulation in the Nearly Closed Bay- (해양유출기름의 확산 시뮬레이션 모델 개발I- 폐쇄만에서의 3차원 흐름특성분석 -)

  • Lee, J.W.;Kim, K.C.;Kang, S.Y.;Doh, D.H.
    • Journal of Korean Port Research
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    • v.11 no.2
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    • pp.241-255
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    • 1997
  • Three dimensional numerical model is used to simulate the circulation patterns in the Gamcheon Bay located in Pusan, Korea and compared with the observed data. The model is forced by winds, tidal elevation at open boundaries, and warm water discharged from the outfall of power plant, Turbulence mixing coefficients are calculated according to a ${\kippa}-{\varepsilon}$ turbulence closure submodel. Temperature, salinty and current are measuted extensively and these measuted data are compared with the simulation results. Eddy-like features exist both in observed data dna simulation results. These eddies are the results of interaction with the weak tidal current, wind driven current and warm water discharges. Compensational deeects are also found to exit such that while surface current is strong, bottom current tends to weaken and vice versa.

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CFD ANALYSIS OF TURBULENT JET BEHAVIOR INDUCED BY A STEAM JET DISCHARGED THROUGH A VERTICAL UPWARD SINGLE HOLE IN A SUBCOOLED WATER POOL

  • Kang, Hyung-Seok;Song, Chul-Hwa
    • Nuclear Engineering and Technology
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    • v.42 no.4
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    • pp.382-393
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    • 2010
  • Thermal mixing by steam jets in a pool is dominantly influenced by a turbulent water jet generated by the condensing steam jets, and the proper prediction of this turbulent jet behavior is critical for the pool mixing analysis. A turbulent jet flow induced by a steam jet discharged through a vertical upward single hole into a subcooled water pool was subjected to computational fluid dynamics (CFD) analysis. Based on the small-scale test data derived under a horizontal steam discharging condition, this analysis was performed to validate a CFD method of analysis previously developed for condensing jet-induced pool mixing phenomena. In previous validation work, the CFD results and the test data for a limited range of radial and axial directions were compared in terms of profiles of the turbulent jet velocity and temperature. Furthermore, the behavior of the turbulent jet induced by the steam jet through a horizontal single hole in a subcooled water pool failed to show the exact axisymmetric flow pattern with regards to an overall pool mixing, whereas the CFD analysis was done with an axisymmetric grid model. Therefore, another new small-scale test was conducted under a vertical upward steam discharging condition. The purpose of this test was to generate the velocity and temperature profiles of the turbulent jet by expanding the measurement ranges from the jet center to a location at about 5% of $U_m$ and 10 cm to 30 cm from the exit of the discharge nozzle. The results of the new CFD analysis show that the recommended CFD model of the high turbulent intensity of 40% for the turbulent jet and the fine mesh grid model can accurately predict the test results within an error rate of about 10%. In this work, the turbulent jet model, which is used to simply predict the temperature and velocity profiles along the axial and radial directions by means of the empirical correlations and Tollmien's theory was improved on the basis of the new test data. The results validate the CFD model of analysis. Furthermore, the turbulent jet model developed in this study can be used to analyze pool thermal mixing when an ellipsoidal steam jet is discharged under a high steam mass flux in a subcooled water pool.

The Effect of Nozzle Collar on Single Phase and Boiling Heat Transfer by Planar Impinging Jet (평면 충돌제트에서 노즐 깃이 단상 및 비등 열전달에 미치는 영향)

  • Shin Chang Hwan;Yim Seong Hwan;Wu Seong Je;Cho Hyung Hee
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.29 no.7 s.238
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    • pp.878-885
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    • 2005
  • The water jet impingement cooling is one of the techniques to remove the heat from high heat flux equipments. Local heat transfer of the confined water impinging jet and the effect of nozzle collar to enhance the heat transfer are investigated in the fee surface jet and submerged jet. Boiling is initiated from the farthest downstream and increase of the wall temperature is reduced with developing boiling, forming the flat temperature distributions. The reduction in the nozzle-to-surface distance fur H/W$\le$1 causes significant increases and distribution changes of heat transfer. Developed boiling reduces the differences of heat transfer for various conditions. The nozzle collar is employed at the nozzle exit. The distances from heated surface to nozzle collar, Hc are 0.25W, 0.5W and 1.0W. The liquid film thickness is reduced and the velocity of wall jet increases as decreased spacing of collar to heated surface. Heat transfer is enhanced fur region from the stagnation to x/W$\~$8 in the free surface jet and to x/W$\~$5 in the submerged jet. For nucleate boiling region of further downstream, the heat transfer by the nozzle collar is decreased in submerged jet comparing with higher velocity condition. It is because the increased velocity by collar is de-accelerated downstream.

The Effect of Nozzle Collar on Single Phase and Boiling Heat Transfer by Planar Impinging Jet (평면 충돌제트에서 노즐 깃이 단상 및 비등 열전달에 미치는 영향)

  • Shin, Chang-Hwan;Yim, Seong-Hwan;Wu, Seong-Je;Cho, Hyung-Hee
    • Proceedings of the KSME Conference
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    • 2004.04a
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    • pp.1452-1457
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    • 2004
  • The water jet impingement cooling is one of the techniques to remove heat from high heat flux equipments. We investigate the local heat transfer of the confined water impinging jet and the effect of nozzle collar to enhance the heat transfer in the free surface jet and submerged jet. Boiling is initiated from the furthest downstream and the wall temperature increase is reduced with developing boiling, forming the flat temperature distributions. The reduction in the nozzle-to-surface distance for $H/W{\leq}1$ causes the significant increases and distribution changes in heat transfer. Developed boiling reduces the differences in heat transfer for various conditions. The nozzle collar is employed at the nozzle exit. The distances from heated surface to guide plate, $H_c$ are 0.25W, 0.5W and 1.0W. The liquid film thickness is reduced and the velocity of wall jet increase as decreased spacing of collar to heated surface. Heat transfer is enhanced for region from the stagnation to $x/W{\sim}8$ in the free surface jet and to $x/W{\sim}5$ in the submerged jet. For nucleate boiling region of further downstream, the heat transfer by the nozzle collar is decreased in submerged jet compare with higher velocity condition. It is because the increased velocity by collar is de-accelerated at downstream.

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Heat Flux Measurements in High Velocity Oxygen-Fuel Torch Flow for Testing High Thermal Materials (고온 재료 테스트를 위한 고속 산소 연료 토치 흐름에서의 열유속 측정)

  • Chinnaraj, Rajesh Kumar;Choi, Seong Man;Hong, Seong Min
    • Journal of the Korean Society of Propulsion Engineers
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    • v.25 no.2
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    • pp.34-41
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    • 2021
  • A commercial HVOF torch (originally designed for coating applications) has been modified as a high temperature flow source for material testing. In this study, a water cooled commercial Gardon gauge was used to measure heat fluxes at four locations away from the nozzle exit. The cooling water temperature data were used to calculate calorimetric heat fluxes at the same locations. The heat fluxes from both methods were compared and the calorimetric heat fluxes were found to be many times higher than the Gardon gauge heat fluxes. A hypothesis is applied to the calorimetric method to understand the discrepancy seen between the methods. The Gardon gauge heat fluxes are seen to be in the range of the hypothesized calorimetric calculations. This can be considered as a considerable validation for the hypothesis, but further refinement needed using appropriate numerical models.

Numerical Study on the Thermal NOx Reduction by Addition of Moisture in LNG Flame (가습 공기의 LNG 화염 Thermal NOx 저감의 수치 해석적 연구)

  • Shin, Mi-Soo;Park, Mi-Sun;Jang, Dong-Soon
    • Journal of Korean Society of Environmental Engineers
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    • v.36 no.12
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    • pp.837-842
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    • 2014
  • A computer program is developed for the prediction of NO generation by the addition of water moisture and water electrolysis gas in LNG-fired turbulent reacting flow. This study is the first part to deal with the moisture effect on NO generation. In this study, parametric investigation has been made in order to see the reduction of thermal NO as a function of amount of moisture content in a LNG-fired flame together with the swirl and radiation effect. First of all, calculation results show that the flame separation together with the NO concentration separation are observed by the typical flow separation due to strong swirl flow. With a fixed amount of air, the increased amount of water moisture from 0 to 10% by 2% interval shows the decrease of NO concentration and flame temperature at exit are from $973^{\circ}C$ and 139 ppm to $852^{\circ}C$ and 71 ppm. The radiation effects on the generation on NO appears more dominant than swirl strength over the range employed in this study. However, for the strong swirl flow employed in this study, the flow separation cause the relatively high NO concentration observed near exit after peak concentration in the front side of the combustor.

Conceptual Design of Underwater Jet Propulsion System using Catalytic Decomposition of Hydrogen Peroxide (과산화수소의 촉매 분해를 활용한 수중 제트 추진 시스템 개념 설계)

  • Baek, Seungkwan;Kang, Hongjae;Ahn, Byeonguk;Yun, Yongtae;Lee, Jaeho;Kwon, Sejin
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2017.05a
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    • pp.120-127
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    • 2017
  • High temperature oxygen and water vapor was generated from catalytic decomposition of rocket grade highly concentrated hydrogen peroxide, and monopropellant thruster system was developed and applied into space propulsion system. In this research, background research and conceptual design of underwater propulsion system using catalytic decomposition of hydrogen peroxide was progressed. Two types of system was designed with different steam injection methods. Propulsion system that has ring-type steam injector was manufactured and performance estimation of system was performed with different nozzle exit area. Performance evaluation with central steam injection type jet engine will be progressed in the future.

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Thermally Stratified Hot Water Storage (태양열의 성층축열과 주택이용에 관한 연구(성층축열))

  • Pak, Ee-Tong
    • Solar Energy
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    • v.10 no.3
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    • pp.3-12
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    • 1990
  • This paper deals with experimental research to increase thermal storage efficiency of hot water stored in an actual storage tank for solar application. The effect of increased energy input rate due to stratification has been discussed and illustrated through experimental data, which was taken by changing dynamic and geometric parameters. Ranges of the parameters were defined for flow rate, the ratio of diameter to height of the tank and inlet-exit water temperature difference. During the heat storage, when the flow was lower, the temperature difference was larger and the ratio of diameter to height of the tank was higher, the momentum exchange decreased. As for this experiment, when the flow rate was 8 liter/min, the temperature difference was $30^{\circ}C$ and the ratio of diameter to height of the tank was 3, the momentum exchange was minimized resulting in a good thermocline and a stable stratification. In the case of using inlet ports, if the modified Richardson number was less than 0.004, full mixing occured and so unstable stratification occured, which mean that this could not be recommended as storage through thermal stratification. Using a distributor was better than using inlet ports to form a sharp thermocline and to enhance the stratification. It was possible to get storage efficiency of 95% by using the distributor, which was higher than a storage efficiency of 85% obtained by using inlet ports in same operation condition. Furthermore, if the distributor was manufactured so that the mainpipe decreases in diameter toward the dead end to maintain constant static pressure, it might be predicted that further stable stratification and higher storage efficiency are obtainable(ie:more than 95%).

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Rigorous Modeling and Simulation of Multi-tubular Reactor for Water Gas Shift Reaction (Water Gas Shift Reaction을 위한 Multi-tubular Reactor 모델링 및 모사)

  • Park, Junyong;Choi, Youngjae;Kim, Kihyun;Oh, Min
    • Korean Chemical Engineering Research
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    • v.46 no.5
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    • pp.931-937
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    • 2008
  • Rigorous multiscale modelling and simulation of the MTR for WGSR was carried out to accurately predict the behavior of process variables and the reactor performance. The MTR consists of 4 fixed bed tube reactors packed with heterogeneous catalysts, as well as surrounding shell part for the cooling purpose. Considering that fluid flow field and reaction kinetics give a great influence on the reactor performance, employing multiscale methodology encompassing Computational Fluid Dynamics (CFD) and process modeling was natural and, in a sense, inevitable conclusion. Inlet and outlet temperature of the reactant fluid at the tube side was $345^{\circ}C$ and $390^{\circ}C$, respectively and the CO conversion at the exit of the tube side with these conditions approached to about 0.89. At the shell side, the inlet and outlet temperature of the cooling fluid, which flows counter-currently to tube flow, was $190^{\circ}C$ and $240^{\circ}C$. From this heat exchange, the energy saving was achieved for the flow at shell side and temperature of the tube side was properly controlled to obtain high CO conversion. The simulation results from this research were accurately comparable to the experimental data from various papers.