Investigation on wave system matching of two-phase pressure oscillation tube

The cavitation phenomenon of the self-resonating waterjet for the modulation of erosion characteristics is investigated in this paper. A three-dimensional computational fluid dynamics (CFD) model was developed to analyze the unsteady characteristics of the self-resonating jet. The numerical model employs the mixture two-phase model, coupling the realizable turbulence model and Schnerr–Sauer cavitation model. Collected data from experimental tests were used to validate the model. Results of numerical simulations and experimental data frequency bands obtained by the Fast Fourier transform (FFT) method were in very good agreement. For better understanding the physical phenomena, the velocity, the pressure distributions, and the cavitation characteristics were investigated. The obtained results show that the sudden change of the flow velocity at the outlet of the nozzle leads to the forms of the low-pressure zone. When the pressure at the low-pressure zone is lower than the vapor pressure, the cavitation occurs. The flow field structure of the waterjet can be directly perceived through simulation, which can provide theoretical support for realizing the modulation of the erosion characteristics, optimizing nozzle structure.

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Two-Phase Flows in Mini-/Micro-Gas Flow Channels of PEM Fuel Cells

Volume 6B: Energy ◽

10.1115/imece2013-66070 ◽

2013 ◽

Author(s):

Sung Chan Cho ◽

Yun Wang

Keyword(s):

Pressure Drop ◽

Gas Flow ◽

Fluid Model ◽

Pem Fuel Cells ◽

Two Phase ◽

Micro Gas Flow ◽

Two Fluid Model ◽

The Impact ◽

Two Fluid ◽

Phase Pressure

In this paper, two-phase flow dynamics in a micro channel with various wall conditions are both experimentally and theoretically investigated. Annulus, wavy and slug flow patterns are observed and location of liquid phase on different wall condition is visualized. The impact of flow structure on two-phase pressure drop is explained. Two-phase pressure drop is compared to a two-fluid model with relative permeability correlation. Optimization of correlation is conducted for each experimental case and theoretical solution for the flows in a circular channel is developed for annulus flow pattern showing a good match with experimental data in homogeneous channel case.

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A Study on the Hydrodynamic Load in a Water Pool When Discharged Air Forms a Bubble Cloud

Volume 4: Fluid Structure Interaction, Parts A and B ◽

10.1115/pvp2006-icpvt-11-93281 ◽

2006 ◽

Author(s):

Ken Uchida ◽

Seijiro Suzuki

Keyword(s):

Void Fraction ◽

Pressure Oscillation ◽

Numerical Results ◽

Numerical Dissipation ◽

Hydrodynamic Load ◽

Water Pool ◽

Two Phase ◽

Bubble Cloud ◽

Water Region ◽

Media Layer

This paper presents a numerical and qualitative study on the expected hydrodynamic load-reducing effect of bubbly media near a volumetrically oscillating bubble. In this study, the bubble or bubble cloud is assumed to be spherically symmetric, and its motion is analyzed as a one-dimensional compressible two-phase flow in the radial direction in spherical coordinates. We adopted the CCUP (CIP-Combined Unified Procedure) method, which is a unified analysis method for both compressible and incompressible fluids proposed by Yabe et al. (1991) in order to treat interaction among gas, liquid, and two-phase media, and to avoid large numerical dissipation at density discontinuities. To verify the analysis program we developed, we analyzed free oscillations of a bubble with a unity void fraction and of a bubble cloud with an initial void fraction of 0.5, and found that the natural frequency from numerical results are well reproduced with an error of 0.9% for the bubble and 5% for the bubble cloud as compared to those obtained on a theoretical basis. Using this method, we analyzed the free oscillation of a bubble cloud in which a bubble with a unity void fraction is covered by a bubbly media layer with an initial void fraction of 0.5. Numerical results show that the amplitude of pressure oscillation inside the bubble is about halved, and that a higher mode of oscillation appears when a bubbly media layer covers the bubble. The measured results from a blowdown test we previously reported also shows a similar higher mode of oscillation. The amplitude of pressure oscillation in the water region was apparently reduced when a thick bubbly media layer covers the bubble. Thus, if the bubbly media is ejected from sparger holes prior to the ejection of a high-pressure bubble, the bubbly media might reduce the hydrodynamic load induced in a water pool made by volumetric oscillation of the bubble.

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Discussion: “Prediction of Two-Phase Pressure Drop and Density Distribution From Mixing Length Theory” (Levy, S., 1963, ASME J. Heat Transfer, 85, pp. 137–150)

Journal of Heat Transfer ◽

10.1115/1.3686034 ◽

1963 ◽

Vol 85 (2) ◽

pp. 150-150

Author(s):

P. Lottes

Keyword(s):

Heat Transfer ◽

Pressure Drop ◽

Density Distribution ◽

Mixing Length ◽

Two Phase ◽

Mixing Length Theory ◽

Phase Pressure

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An Experimentally Validated Model for Two-Phase Sudden Contraction Pressure Drop in Microchannel Tube Headers

1st International Conference on Microchannels and Minichannels ◽

10.1115/icmm2003-1026 ◽

2003 ◽

Author(s):

John Wesley Coleman

Keyword(s):

Pressure Loss ◽

Accurate Determination ◽

Time Data ◽

Two Phase ◽

Pressure Transducers ◽

Pressure Losses ◽

Mass Fluxes ◽

Data Points ◽

Minor Losses ◽

Phase Pressure

This paper presents the results of an experimental investigation of two-phase pressure loss of R134a in microchannel headers using various end-cut techniques. Novel experimental techniques and test sections were developed to enable the accurate determination of the minor losses without obfuscating the problem with a lengthwise pressure gradient. This technique represents a departure from approaches used by other investigators that have extrapolated minor losses from air-water experiments and the combined effects of expansion, contraction, deceleration, and lengthwise pressure gradients. Pressure losses were recorded over the entire range of qualities from 100% vapor to 100% liquid. In addition, the tests were conducted for five different refrigerant mass fluxes between 185 kg/m2-s and 785 kg/m2-s using two differnt end-cut techniques. More than 790 data points were recorded to obtain a comprehensive understanding of the effects of mass flux and quality on minor pressure losses. High accuracy instrumentation such as coriolis mass flowmeters, RTDs, pressure transducers, and real-time data analyses were used to ensure accuracy in the results. The results show that many of the commonly used correlations for estimating two-phase pressure losses significantly underpredict the pressure losses found in compact microchannel tube headers. Furthermore, the results show that the end-cut technique can substantially affect the pressure losses in microchannel headers. A new model for estimating the pressure loss in microchannel headers is presented and a comparison of the end-cut techniques on the minor losses is reported.

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