• Title/Summary/Keyword: Flow Condensation

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Effect of Condensation on Spray Characteristics of Simplex Swirl Nozzle (응축이 심플렉스 와류 노즐의 분무 특성에 미치는 영향)

  • Koh, Kwang-Uoong;Lee, Sang-Yong
    • Proceedings of the KSME Conference
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    • 2001.06e
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    • pp.107-112
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    • 2001
  • The effect of ambient gas (steam) condensation on swirl spray characteristics were studied experimentally for low subcooling condition of the liquid. The configuration of the liquid(water) sheet and the breakup modes were examined. Also variation of the discharge coefficient, breakup length, local and the cross-sectional area-averaged SMD of droplets with the liquid flow(injection) rate were obtained. The perforation breakup mode appears dominant with condensation while the aerodynamic wave breakup mode is dominant without condensation(in the air environment). The discharge coefficient, breakup length and the mean drop sizes decrease in a same manner with increasing of the liquid flow rate for both cases(with and without condensation). The condensation effects are insignificant with the discharge coefficient. However, the local and cross-sectional area-averaged SMD are larger and the breakup length becomes shorter in the steam environment. The spray angle predicted from the volumetric flux distribution along the radial direction of the sprays in the steam environment becomes larger with condensation.

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Film Flow Analysis for a Vertical Evaporating Tube with Inner Evaporation and Outer Condensation (내부와 외부에서 증발과 응축이 발생하는 수직관에 대한 유동 해석)

  • Park, Il-Seouk
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.32 no.8
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    • pp.621-628
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    • 2008
  • A numerical study for the flow, heat and mass transfer characteristics of the evaporating tube with the films flowing down on both the inside and outside tube walls has been carried out. The condensation occurs along the outside wall while the evaporation occurs at the free surface of the inside film. The transport equations for momentum and energy are parabolized by the boundary-layer approximation and solved by using the marching technique. The calculation domain of 2 film flow regions (evaporating and condensation films at the inside and outside tube wall respectively) and tube wall is solved simultaneously. The coupling technique for the problem with the 3 different regions and the 2 interfaces of them has been developed to calculate the temperature field. The velocity and temperature fields and the amount of the condensed and evaporated mass as well as the position where the evaporating film is completely dried out are successfully predicted for various inside pressures and inside film inlet flow rates.

Visualization of cross-sectional two-phase flow structure during in-tube condensation (관내 응축 시 2상유동 단면구조의 가시화)

  • Pusey, Andree;Kim, Hyungdae
    • Journal of the Korean Society of Visualization
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    • v.14 no.2
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    • pp.18-24
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    • 2016
  • This paper presents an experimental investigation to visualize cross-sectional two-phase flow structure and identify liquid-gas interface for condensation of steam at a low mass flux in a slightly inclined tube using the axial-viewing technique, which permits to look directly into flow during condensation of steam. In this technique, two-phase flow is viewed along the axis of a pipe by locating a high-speed video camera in front of a viewer that is fitted at the outlet of the pipe. A short section of the pipe is illuminated and is recorded through the viewer, which is kept free of liquid by mildly introducing air. Experiments were conducted in a pipe of 19.05 mm in inner diameter at atmospheric pressure. Cross-sectional two-phase flow structure is obtained at a steam mass flux of $2.62kg/m^2s$ as a function of steam quality in the range from 0.5 to 0.9. The results show that stratified-wavy flow is a unique flow pattern observed in the scope of the present study. Condensate film thickness, stratification angle and void fraction were measured from the obtained flow structure images. Finally, heat transfer coefficient was calculated using the measurement data and discussed in comparison with existing correlations.

Interfacial Condensation Heat Transfer for Countercurrent Steam-Water Stratified Flow in a Circular Pipe

  • Chu, In-Cheol;Chung, Moon-Ki;Yu, Seon-Oh;Chun, Moon-Hyun
    • Nuclear Engineering and Technology
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    • v.32 no.2
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    • pp.142-156
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    • 2000
  • An experimental study of steam condensation on a subcooled thick water layer (0.018 ~0.032 m) in a countercurrent stratified flow has been performed using a nearly horizontal circular pipe. A total of 103 average interfacial condensation heat transfer coefficients were obtained and parametric effects of steam and water flow rates and the degree of subcooling on condensation heat transfer were examined. The measured local temperature and velocity distributions in the thick water layer revealed that there was a thermal stratification due to the lack of full turbulent thermal mixing in the lower region of the water layer Two empirical Nusselt number correlations, one in terms of average steam and water Reynolds numbers, and the water Prandtl number, and the other in terms of the Jakob number in place of the Prandtl number, which agree with most of the data within $\pm$ 25%, were developed based on the bulk flow properties. Comparisons of the present data with existing correlations showed that the present data were significantly lower than the values predicted by existing correlations.

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Flow Condensation Inside Mini-Channels (II) -Experimental Study of the Circular and Rectangular Channels- (작은 유로 내에서의 흐름응축 열전달 (II) -원형 및 사각유로에서의 실험적 연구-)

  • Shin, Jeong-Seob;Kim, Moo-Hwan
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.28 no.11
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    • pp.1432-1439
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    • 2004
  • By using unique experimental techniques and careful construction of the experimental apparatus, the characteristics of the local heat transfer were investigated using the condensing R134a two-phase flow, in horizontal single mini-channels. The circular channels (D$_{h}$=0.493, 0.691, and 1.067 mm) and rectangular channels (Aspect Ratio=1.0, D$_{h}$=0.494, 0.658, and 0.972 mm) were tested and compared. Tests were performed for a mass flux of 100, 200, 400, and 600 kg/$m^2$s, a heat flux of 5 to 20 ㎾/$m^2$, and a saturation temperature of 4$0^{\circ}C$. In this study, effect of heat flux, mass flux, vapor qualities, hydraulic diameter, and channel geometry on flow condensation are investigated and the experimental local condensation heat transfer coefficients are shown. The experimental data of condensation Nusselt number are compared with existing correlations.ons.

A Study on the Control of Water Flow and Water Temperature in the Radiant Cooling System through Simulations (시뮬레이션을 통한 바닥복사냉방 시스템의 공급유량 및 냉수온도 제어에 관한 연구)

  • 김용이;윤혜림;여명석
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.13 no.6
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    • pp.532-540
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    • 2001
  • The objectives of this study are to analyze the control variables according to condensation occurrence, to find the range in floor surface temperature and frequency of condensation, and to evaluate the control methods through simulations when the radiant heating system is used for cooling. Through the simulation analysis the control methods such as on/off control, variable flow control and outdoor reset with indoor temperature feedback control are evaluated and compared. The results show that the lowest floor surface temperature is around $23^{\circ}C$, the surface condensation can be prevented by controlling indoor humidity within 20g/kg(DA0, and that outdoor reset with indoor temperature feedback control is more appropriate than on/off control and variable flow control with regard to prevention of the condensation and thermal comfort.

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Experimental Study on Stream Turbine Cascade Flow (증기터빈 익렬유동에 관한 실험적 연구)

  • 권순범;윤의수;김병지
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.8
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    • pp.2177-2183
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    • 1994
  • The rapid expansion or condensible gas such as moist air of steam gives rise to nonequilibrium condensation. As a result of irreversibility of condensation process in the supersonic cascade flow of low pressure steam turbine, the entropy of the flow is increased, and the efficiency of the turbine is decreased. In the present study, to investigate the flow of moist air in 2-dimensional cascade made as the configuration of the tip section of the last actual steam turbine moving blade, the static pressure at both sides of pressure and suction of blade are measured by static pressure taps and the distribution of Mach number on both surfaces of the blade are obtained by using the measured static pressure. Also, the flow field is visualized by a schlieren system. From the experimental results, the effects of the stagnation temperature and specific humidity on the flow properties in a 2-dimensional stationary cascade of a practical steam turbine blade are clearly identified.

Thw Characteristic of Supersonic Flow with Condensation along a Wavy Wall of Small Amplitute in Channel (미소진폭 파형벽을 가진 유로내에서 凝縮을 수반하는 超音速 유동의 特性 - 수치해석 결과)

  • 김병지;권순범
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.16 no.10
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    • pp.1990-1997
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    • 1992
  • The characteristic of supersonic flow with condensation along a wavy wall of small amplitude in channel is investigated through the direct marching method of characteristics. The very complex problem that may appear where the overlapping of the same family characteristics occurs, can be satisfactorily solved by means of the modified method suggested by Zucrow. In the present study for the case of supersonic moist air flow, the dependency of location of formation and reflection of oblique shock wave generated by the wavy wall, and the distributions of flow properties, on the relative humidity and temperature at the entrance of wavy wall is clarified by plots of streamline, ios-Mach umber and ios-flow properties. Also, it is confirmed that the wavy wall plays an important key role in the formation of oblique shock wave, and that the effect of condensation on the flow field appears apparently.

The Study of Supersonic Flow with Condensation Along a Wavy Wall in a Channel (波形壁 流路내에서 凝縮이 수반되는 超音速유동에 대한 硏究)

  • 권순범;김병지;김흥균
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.2
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    • pp.424-431
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    • 1994
  • The characteristics of supersonic flow with condensation along a wavy wall of a small Smplitude in a channel is investigated experimentally and numerically. In the present study for the case of supersonic moist air flow, the dependency of location of reflection of oblique shock wave generated by the wavy wall, and the distributions of flow properties in the flow field, on the stagnation relative humidity and temperature is clarified by the plots of streamline, iso-Mach number and iso-flow properties of numerical result and the schlieren photographs of experiment. And. experimental and numerical results are in good agreement.

A Study on the Onset of Condensation in a Supersonic Nozzle of Constant Expansion Rate (팽창율이 일정한 초음속 노즐흐름의 응축개시에 관한 연구)

  • 김병지;권순범;이은수
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.14 no.2
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    • pp.463-469
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    • 1990
  • A rapid expansion of moist air of condensible gas through a supersonic nozzle gives rise to condensation of nonequilibrium and equilibrium processes. Because most of the effects of condensation on the flow are caused by process of nonequilibrium condensation, it is very important to know the onset. condition of nonequilibrium condensation. In the present study, the relation between the initial relative stagnation humidity and the onset Mach number, for the case of the similarity law suggested by Zierep and Lin. Furthermore, the present theoretical result number is compared with the experimental, numerical and other results.