A Visual and Photographic Study of the Inception of Vaporization in Adiabatic Flow

1964 ◽  
Vol 86 (2) ◽  
pp. 257-261 ◽  
Author(s):  
E. P. Mikol ◽  
J. C. Dudley
Keyword(s):  
Experimental Method ◽  
Two Phase Flow ◽  
Operating Conditions ◽  
Phase Flow ◽  
Two Phase ◽  
Adiabatic Flow ◽  
Index Data ◽  
Flow Phenomena ◽  
Glass Tubes

Data and observations obtained during the study of two-phase flow phenomena for refrigerants flowing in small bore copper and glass tubes have been examined for their significance to the cavitation. Visual and photographic observations have been made of the inception of vaporization and of the movement of the point of inception as operating conditions are varied. Liquid tension has been deduced as occurring in these tests. Liquid tension and cavitation index data are presented. The experimental method is recommended as a means for studying many aspects of the phenomenon of cavitation.

Non-Intrusive Optical Validation of Two-Phase Flow Regimes in a Small Diameter Tube

2014 ◽  
Author(s):  
Darin J. Sharar ◽  
Arthur E. Bergles ◽  
Nicholas R. Jankowski ◽  
Avram Bar-Cohen
Keyword(s):  
Film Thickness ◽  
Flow Regime ◽  
Two Phase Flow ◽  
Small Diameter ◽  
Flow Regimes ◽  
Phase Flow ◽  
Two Phase ◽  
Traditional Use ◽  
Adiabatic Flow ◽  
Flow Pattern Identification

A non-intrusive optical method for two-phase flow pattern identification was developed to validate flow regime maps for two-phase adiabatic flow in a small diameter tube. Empirical measurements of film thickness have been shown to provide objective identification of the dominant two-phase flow regimes, representing a significant improvement over the traditional use of exclusively visual and verbal descriptions. Use of this technique has shown the Taitel-Dukler, Ullmann-Brauner, and Wojtan et al. phenomenological flow regime mapping methodologies to be applicable, with varying accuracy, to small diameter two-phase flow.

Experiment of Adiabatic Two-Phase Flow in an Annulus Under Low-Frequency Vibration

2012 ◽  
Author(s):  
Shao-Wen Chen ◽  
Caleb S. Brooks ◽  
Chris Macke ◽  
Takashi Hibiki ◽  
Mamoru Ishii ◽  
...  
Keyword(s):  
Void Fraction ◽  
Two Phase Flow ◽  
Low Frequency ◽  
Flow Regimes ◽  
Operating Conditions ◽  
Phase Flow ◽  
Two Phase ◽  
Specific Flow ◽  
Low Frequency Vibration ◽  
Fft Analysis

In order to investigate the possible effect of seismic vibration on two-phase flow dynamics and thermal-hydraulics of a nuclear reactor, experimental tests of adiabatic air-water two-phase flow under low-frequency vibration were carried out in this study. An eccentric cam vibration module operated at low motor speed (up to 390rpm) was attached to an annulus test section which was scaled down from a prototypic BWR fuel assembly sub-channel. The inner and outer diameters of the annulus are 19.1mm and 38.1mm, respectively. The two-phase flow operating conditions cover the ranges of 0.03≤<jg> ≤1.46m/s and 0.25≤<jf>≤1.00m/s and the vibration displacement ranges from ±0.8mm to ±22.2mm. Steady-state area-averaged instantaneous and time-averaged void fraction was recorded and analyzed in stationary and vibration experiments. A neural network flow regime identification technique and fast Fourier transformation (FFT) analysis were introduced to analyze the flow regimes and void signals under stationary and vibration conditions. Experimental results reveal possible changes in flow regimes under specific flow and vibration conditions. In addition, the instantaneous void fraction signals were affected and shown by FFT analysis. Possible reasons for the changes include the applied high acceleration and/or induced resonance at certain ports under the specific flow and vibration conditions.

Numerical Simulation and Experimental Validation on the Particle Trajectory in a Solid Propellant Rocket Chamber

2000 ◽  
Author(s):  
Yumin Xiao ◽  
R. S. Amano ◽  
Timin Cai ◽  
Jiang Li
Keyword(s):  
Numerical Simulation ◽  
Experimental Method ◽  
High Speed ◽  
Particle Trajectory ◽  
Two Phase Flow ◽  
Measurement Data ◽  
Special Method ◽  
Phase Flow ◽  
Two Phase ◽  
Particle Injection

Abstract In solid rocket motors (SRMS) using aluminized composite solid propellants and submerged nozzles a two-phase flow pattern is one of the main flow characteristics needs to be investigated. The modeling and validation of two-phase flow are the focus in this research field. In this paper the authors first traced the particle trajectory in a SRM chamber by using numerical method, and then developed a new experimental method to measure the particle trajectory in a SRM chamber to validate the numerical results. The experimental method was based on the RTR (X-ray Real-time Radiography) technique and high-speed motion analyzer. A special method was developed to imitate the particle injection on the propellant surface. The calculation results and measurement data show that the trajectory obtained by numerical simulation was in good agreement with the measured one by imposing proper boundary conditions. For particles with diameter of 75μm, the initial velocity factor of particle is approximately 0.4, and the particles pass through the centerline in both calculation and experiment. The present method can be extended to study the impingement of particles on the wall and other related two-phase flow patterns.

Ex-Situ Characterization of Two-Phase Flow Regimes in Proton-Exchange Membrane Fuel Cells Under Non-Isothermal Conditions

2010 ◽  
Author(s):  
Arganthae¨l Berson ◽  
Jon G. Pharoah
Keyword(s):  
Proton Exchange Membrane ◽  
Two Phase Flow ◽  
Metal Foam ◽  
Flow Regimes ◽  
Proton Exchange ◽  
Operating Conditions ◽  
Ex Situ ◽  
Phase Flow ◽  
Two Phase ◽  
Exchange Membrane

Efficient water management is crucial for the good performances of proton-exchange membrane fuel cells (PEMFCs). The geometric and physical characteristics of the components of a PEMFC as well as operating conditions have an impact on the transport of water through the porous transport layer (PTL) and the two-phase flow regimes in the microchannels. One parameter of importance is the local temperature, which affects properties such as surface tension and is coupled with phase change. Indeed, a temperature difference of about 5K is expected across the PTL, with spatial variations due to the geometry of the flow field plate. We present preliminary results obtained with a first experimental setup for the ex-situ characterization of two-phase flow regimes in the flow channels. Water is pushed through the PTL, which is sandwiched between a porous metal foam and the flow field plate. The air flow rate, temperature and humidity can be controlled. The cell can be heated up by applying an electrical current through the metal foam. A transparent window is located on top of the flow channel. The two-phase flow within the micro-channels is visualized using a high-speed camera and laser-induced fluorescence. Preliminary results obtained under isothermal conditions at room temperature show that different two-phase flow regimes occur in the channels depending on the operating conditions, in good qualitative agreement with data from the literature. Eventually, a new visualization cell is presented that is expected to correct the flaws of the previous design and will allow a better thermal control. It will be possible to adjust the temperature gradient and the mean temperature in order to observe their impact on two-phase flow regimes for different types of PTL and flow rates. The results will provide a better understanding of water transport in PEMFC and benchmark data for the validation of numerical models.

Micro-Scale Two-Phase Flow Heat Transport Device Driven by Electrohydrodynamic Conduction Pumping

2013 ◽  
Author(s):  
Viral K. Patel ◽  
Jamal Seyed-Yagoobi
Keyword(s):  
Heat Transport ◽  
Two Phase Flow ◽  
Operating Conditions ◽  
Electrode Spacing ◽  
Working Fluid ◽  
Phase Flow ◽  
Two Phase ◽  
Micro Scale ◽  
Flow Heat ◽  
Transport Device

Micro-scale two-phase flow heat transport involves specialized devices that are used to remove large amounts of heat from small surface areas. They operate by circulating a working fluid through a heated space which causes phase change from liquid to vapor. During this process, a significant amount of heat is transported away from the heat source. Micro-scale heat transport devices are compact in size and the heat transfer coefficient can be orders of magnitude higher than in macro-scale for similar operating conditions. Thus, it is of interest to develop such devices for cooling of next-generation electronics and other applications with extremely large heat fluxes. The heat transport device presented in this paper is driven by electrohydrodynamic (EHD) conduction pumping. In EHD conduction pumping, when an electric field is applied to a dielectric liquid, flow is induced. The pump is installed in a two-phase flow loop and has a circular 1 mm diameter cross section with electrode spacing on the order of 120 μm. It acts to circulate the fluid in the loop and has a simple yet robust, non-mechanical design. Results from two-phase flow experiments show that it is easily controlled and such electrically driven pumps can effectively be used in heat transport systems.

Design Methodology and Valve Sizing for Heater Drain Systems

2009 ◽  
Author(s):  
Casey Loughrin
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Pressure Losses ◽  
Solution Methods ◽  
Flow Phenomena ◽  
Flow Pressure ◽  
And Control

Heater drain systems in fossil and nuclear power plants have proven to be among the most complex systems to design due to the occurrence of two–phase flow phenomena. The overall performance of heater drain systems directly relates to proper sizing and design of the piping and control valves. Proper sizing is highly dependent upon accurate and conservative calculation of two-phase flow pressure losses. This paper outlines the various options of solution methods available to the engineer and details one possible method which is simple, yet adequate, and based on the homogeneous equilibrium model (HEM) for two phase flow for calculation of heater drain system performance. General comparisons are made to the more complex multi-fluid models, flow regime considerations, and non-equilibrium models.

Numerical Modeling of Two-Phase Flow Distribution Inside Evaporator Headers

2014 ◽  
Vol 6 (3) ◽  
Author(s):  
Miad Yazdani ◽  
Abbas A. Alahyari ◽  
Hailing Wu ◽  
Thomas D. Radcliff
Keyword(s):  
Heat Exchanger ◽  
Two Phase Flow ◽  
Flow Distribution ◽  
Operating Conditions ◽  
Phase Flow ◽  
Predictive Tool ◽  
Two Phase ◽  
Imaging Results ◽  
Discretization Schemes ◽  
Long Time

Two-phase flow distribution inside evaporator headers has been a challenging problem for a long time and having a robust predictive tool could substantially alleviate the costs associated with experimentation with different concepts and configurations. The use of a two-phase CFD model to predict flow distribution inside the header and at the discharge ports is demonstrated in this paper. The numerical domain is comprised of an inlet pipe and a distributor tube representing the header with a series of discharge ports. The flow distribution was initially verified using an air–water experiment, where the two-phase modeling approach, mesh requirements, and discretization schemes were defined. Next, the model was used to predict distribution of R134a in a typical heat exchanger distributor. The flow distribution across the discharge ports was provided to a discretized correlation-based heat exchanger model to predict the temperature and quality distribution along the length of the heat exchanger. The resultant temperature distribution is validated against IR imaging results for various operating conditions and header orientations.

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