• Title/Summary/Keyword: Vertical upward flow

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Flow Analysis of Bubble and Liquid Phase by Vertical Upward Gas Injection (수직상향 기체 주입에 따른 기포 및 액상의 유동분석)

  • 서동표;오율권
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.15 no.9
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    • pp.727-732
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    • 2003
  • In the present study, a PIV measurement and image processing technique were applied in order to investigate the flow characteristics in the gas injected liquid bath. The circulation of liquid was induced by upward bubble flow. Due to the centrifugal force, the flow was well developed near both wall sides than in the center of a bath. The vortex flow irregularly repeated generation and disappearance which helped to accelerate the mixing process. The bubble rise velocity in the bottom region was relatively lower than in the upper region because the energy generated by bubbles' behavior in the region near the nozzle was almost converted into kinetic energy But bubble rise velocity increases with the increase of the axial distance since kinetic energy of rising bubbles is added to buoyancy force. In conclusion, the flow increased bubble rise velocity and the flow of the bottom region became more active.

An Experimental Study on the Heat Transfer Characteristics during the Freezing Process of Water in the Vertical Multi Tube Type Ice Storage Tank (수직다발관형 빙축열 탱크내 물의 응고과정시 열전달특성에 관한 연구)

  • Kim, Y.K.;Yim, C.S.
    • Solar Energy
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    • v.18 no.3
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    • pp.95-105
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    • 1998
  • In this study, basic design data which were required for development of highly efficient ice storage system with low temperature latent heat were experimentally obtained. The ice storage system considered in this study was the one that has been widly used in the developed country and called the ice-on-coil type. Using the system, the ice storage performance for various design parameters which were the flow direction and the inlet temperature of the secondary fluid was tested. In addition, the timewise variation of the interface profiles between the solid and the liquid were visualized, and the heat transfer characteristics of the Phase Change Material(PCM) in the ice storage tank were Investigated. During the freezing processes in the ice storage tank with several vertical tubes, decrease of the heat transfer area and the heat resistance of the ice layer made the increasing rate of ice packing factor(IPF) less. The total freezing energy for the upward flow of the secondary fluid was higher than that for the downward flow. The average ice storage efficiency for the upward flow of the secondary fluid was higher than that for the downward flow.

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A study on the characteristics of evaporation heat transfer of carbon dioxide flowing upward in a vertical smooth tube (이산화탄소의 수직원관 내 상향유동 증발열전달 특성에 관한 연구)

  • Kim, Yong-Jin;Cho, Jin-Min;Kim, Min-Soo
    • Proceedings of the KSME Conference
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    • 2007.05b
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    • pp.2217-2221
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    • 2007
  • Because of the ozone layer depletion and global warming, new alternative refrigerants are being developed. In this study, evaporation heat transfer characteristics of carbon dioxide flowing upward in a vertical tube have been investigated by experiment. Before the test section, a pre-heater is installed to adjust the inlet quality of the refrigerant to a desired value. A smooth tube with outer diameter of 5 mm and length of 1.44 m was selected as a test tube. The test was conducted at mass fluxes of 212 to 530 kg/$m^2s$, saturation temperature of -5 to 20$^{\circ}C$, and heat fluxes of 20 to 45 kW/$m^2$. As the vapor quality and mass fluxes increase, the heat transfer coefficients of carbon dioxide are decreased, and the heat transfer coefficients increase when the heat fluxes and saturation temperatures increase.

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An experimental study on heat transfer characteristics in a vertical micro-fin tube during evaporation process of carbon dioxide flowing upward (이산화탄소의 마이크로 핀관 내 상향유동 증발열전달 특성에 관한 연구)

  • Kim, Yong-Jin;Cho, Jin-Min;Kim, Min-Soo
    • Proceedings of the SAREK Conference
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    • 2007.11a
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    • pp.247-251
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    • 2007
  • Because of the ozone layer depletion and global warming, new alternative refrigerants are being developed. In this study, evaporation heat transfer characteristics of carbon dioxide flowing upward in a vertical micro-fin tube have been investigated by experiment. Before a test section, a pre-heater is installed to adjust the inlet quality of the refrigerant to a desired value. The micro-fin tube with outer diameter of 5 mm and length of 1.44 m was selected as the test section. The test was conducted at mass fluxes of 318 to $530\;kg/m^2s$, saturation temperature of -5 to $5^{\circ}C$, and heat fluxes of 15 to $30\;kW/m^2$. As the vapor quality increases, the heat transfer coefficients of carbon dioxide are increased, and the heat transfer coefficients increase when the heat fluxes and saturation temperatures increase, and there was not much of influence of mass flux on the heat transfer coefficients.

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A Study on the Drag Reduction of Shear Thinning Fluid with Vertical upward Turbulent Flow (전단박화유체의 수직상향 난류유동시 저항감소에 관한 연구)

  • Cha, Kyong-Ok;Kim, Bong-gag;Kim, Jea-Geun
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.22 no.12
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    • pp.1647-1656
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    • 1998
  • The drag reduction is the phenomenon that occurs only when the shear stress from the wall of pipe is beyond the critical point. The drag reduction increase as the molecular weight, concentration of the polymer and Reynolds number increase, but it is limited by Virk's maximum drag reduction asymptote. Because of the strong shear force for the polymer on the turbulent flow, the molecular weight and the drag reduction do not decrease. Such mechanical degradation of the polymer occurs in all polymer solvent systems. This paper is to identify and develop high performance polymer additives for fluid transportations with the benefits of turbulent drag reduction. In addition, drag reduction in vertical flow by measuring the pressure drop and local void fraction on vertical-up flow of close system is evaluated.

Modeling and simulation of air-water upward annular flow characteristics in a vertical tube using CFD

  • Anadi Mondal;Subash L Sharma
    • Nuclear Engineering and Technology
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    • v.56 no.7
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    • pp.2881-2892
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    • 2024
  • Annular flow refers to a special type of two-phase flow pattern in which liquid flows as a thin film at the periphery of a pipe, tube, or conduit, and gas with relatively high velocity flows at the center of the flow section. This gas also includes dispersed liquid droplets. The liquid film flow rate continuously changes inside the tube due to two processes-entrainment and deposition. To determine the liquid holdup, pressure drop, the onset of dryout, and heat transfer characteristics in annular flow, it is important to have proper knowledge of flow characteristics. Especially a better understanding of entrainment fraction is important for the heat transfer and safe operation of two-phase flow systems operating in an annular two-phase flow regime. Therefore, the objective of this work is to develop a computational model for the simulation of the annular two-phase flow regime and assess the various existing models for the entrainment rate. In this work, Computational Fluid Dynamics (CFD) in ANSYS FLUENT has been applied to determine annular flow characteristics such as liquid film thickness, film velocity, entrainment rate, deposition rate, and entrainment fraction for various gas-liquid flow conditions in a vertical upward tube. The gas core with droplets was simulated using the Discrete Phase Model (DPM) which is based on the Eulerian-Lagrangian approach. The Eulerian Wall Film (EWF) model was utilized to simulate liquid film on the tube wall. Three different models of Entrainment rate were implemented and assessed through user-defined functions (UDF) in ANSYS. Finally, entrainment for fully developed flow was determined and compared with the experimental data available in the literature. From the simulations, it was obtained that the Bertodano correlation performed best in predicting entrainment fraction and the results were within the ±30 % limit when compared to experimental data.

Helium-Air Exchange Flow with Fluids Interaction (유체간섭을 동반하는 헬륨과 공기의 치환류)

  • T.I. Kang
    • Journal of Advanced Marine Engineering and Technology
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    • v.21 no.4
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    • pp.372-380
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    • 1997
  • This paper describes experimental investigations of helium-air exchange flows through parti¬tioned opening and two-opening. Such exchange flows may occur following rupture accident of stand pipe in high temperature gas cooled reactor. A test vessel with the two types of small open¬ing on top of test cylinder is used for experiments. An estimation method of mass increment is developed and applied to measure the exchange flow rate. A technique of flow visualization by Mach-Zehnder interferometer is provided to recognize the exchange flows. In the case of exchange flow through the partitioned opening, flow passages of upward flow of the helium and downward flow of the air within the opening are separated by vertical partition, and the two flows interact out of entrance and exit of the opening. Therefore, an experiment of the exchange flow through two-opening is made to investigate effect of the fluids interaction of the partitioned opening sys¬tem. As a result of comparison of the exchange flow rates between the two types of the opening system, it is found that the exchange flow rate of the two-opening system is larger than that of the partitioned opening system due to absence of the effect of fluids interaction. Finally, the fluids interaction between the upward and downward flows through the partitioned opening is found to be an important factor on the helium-air exchange flow.

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A Study on the Characteristics of Natural Convection in a Partially Opened Enclosure with a Heat Source (발열체와 부분 열림 수직벽을 갖는 사각 공간내 자연대류 특성 해석)

  • Shim, Dong-Sik;Kang, Bo-Seon;Cha, Dong-Jin;Ju, Won-Jong
    • Proceedings of the KSME Conference
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    • 2000.04b
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    • pp.322-327
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    • 2000
  • Natural convection heat transfer in an enclosure with an opening in the right vertical wall and a heat source at the bottom surface is investigated using a holographic interferometric technique. The effects of the opening length, divider length attached to the top wall, and heater temperature on the temperature distribution are examined. The openging length as well as the divider length greatly affects the degree of inflow and outflow of air. With a small opening, the opening doesn't affect much the upward warm air flow resulting in the symmetric temperature distribution. On the other hand, with the increase of the opening length, the inward cold flow moves the upward flow to the left direction. With the increase of the divider length, temperature in the lower region of enclosure becomes higher for the small opening and lower for the large opening.

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Experimental Study on Flow Patterns and Pressure Drop Characteristics of Ice Slurry in Small Size Pipe (2) (소구경 배관내 아이스슬러리의 유동형상 및 압력강하 특성에 관한 실험적 연구(2))

  • 이동원;윤찬일;주문창
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.14 no.5
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    • pp.391-397
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    • 2002
  • Pressure drop were experimentally investigated for ice slurry flowing in the acrylic pipes with inner diameter of 24 mm. Ice slurry was made from 6.5% ethylene glycol-water solution, and the pipes is consisted of horizontal, vertical (upward and downward) and $90^{\circ}$ elbow pipe. The ice Packing factor (IPF) and the flow rate of the experiments were varied from 0 to 30% and from 5 to 70kg/min respectively The measured pressure drop in various pipe positions were compared with those for the solution flow (IPF=0). The pressure drop was larder than that for solution flows as the IPF increased when the flow rate was low or very high. Sharp increases in pressure drop were observed for the cases when IPF is more than 70% in horizontal and vertical pipes, whereas the pressure drop increased with the IPF simultaneously in an elbow pipe.