scholarly journals FLOW PATTERNS OF THE ESTER OIL-REFRIGERANT R134A MIXTURE FLASHING FLOW THROUGH A SMALL DIAMETER TUBE

2008 ◽  
Vol 7 (1) ◽  
pp. 41
Author(s):  
H. O. S. Castro ◽  
J. L. Gasche ◽  
W. P. Conti ◽  
E. D. R. Vieira
Keyword(s):  
Pressure Gradient ◽  
Small Diameter ◽  
Flow Patterns ◽  
Foam Formation ◽  
Two Phase ◽  
Mixture Flow ◽  
Experimental Apparatus ◽  
Mass Fractions ◽  
Mass Flow Rates ◽  
Temperature And Pressure

This work presents an experimental investigation of the ester oil ISO VG10-refrigerant R134a mixture flashing flow with foam formation through a straight horizontal 3.22 mm-diameter-6.0 m- long tube. An experimental apparatus was designed to allow the measurement of both pressure and temperature profiles along the tube as well as the visualization of the flow patterns. Tests were performed at different mass flow rates, several refrigerant mass fractions at the inlet of the flow, and inlet mixture temperatures around 28 and 39 °C. A liquid mixture flow with constant temperature and pressure gradient could be noticed at the inlet of the tube. As the flow proceeded towards the exit of the tube the pressure drop produced a reduction of the refrigerant solubility in the oil yielding to formation of the first bubbles. Initially, small and few bubbles could be noticed and the flow behaved as a conventional two-phase flow. Eventually, the bubble population increased and foam flow was observed at the exit of the tube. Due to the great formation of bubbles, both the temperature and pressure gradient of the mixture were greatly reduced in this region of the flow.

Experimental Visualization and Numerical Simulation of Liquid-Gas Two-Phase Flows in a Horizontal Pipe

2017 ◽  
Author(s):  
Milad Darzi ◽  
Chanwoo Park
Keyword(s):  
Numerical Simulation ◽  
Gas Flow ◽  
Cfd Simulation ◽  
Glass Tube ◽  
Flow Patterns ◽  
Two Phase Flows ◽  
Two Phase ◽  
Mixture Flow ◽  
Horizontal Pipe ◽  
Flow Rates

This paper presents the results of both visualization experiment and numerical simulation for two-phase (water-air mixture) flows in a horizontal tube. A visualization experimental setup was used to observe various two-phase flow patterns for different flow rates of water/air mixture flow in a glass tube of 12 mm in diameter. Total of 303 experimental data points were compared with Mandhane’s flow map. Most of the data for stratified, plug and slug flows were found to be in good agreement. However, annular flow was observed for relatively lower gas flow rates and also wavy flow occurred at relatively higher liquid flow rates in this experiment. A three-dimensional Computational Fluid Dynamics (CFD) simulation was performed using OpenFOAM employing “interFoam” as the solver to simulate the two-phase flows in horizontal pipe based on Volume-Of-Fluid (VOF) method. The simulated and experimentally observed flow patterns for the same set of superficial velocities shows acceptable similarities for stratified, wavy, plug, slug and annular flows. Also, the computed values of the void fraction and pressure drop for the numerical simulations shows reasonable agreement with well-known correlations in literature.

Two-Phase Flow Regime Transitions in Microchannel Tubes: The Effect of Hydraulic Diameter

2000 ◽  
Author(s):  
John W. Coleman ◽  
Srinivas Garimella
Keyword(s):  
Flow Regime ◽  
Mass Flux ◽  
Two Phase Flow ◽  
Small Diameter ◽  
Flow Patterns ◽  
Hydraulic Diameter ◽  
Intermittent Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Mechanisms

Abstract An experimental investigation of two-phase flow mechanisms during condensation of refrigerant R134a in small diameter round and rectangular tubes was conducted. A 4.91 mm round tube, and four round tubes with hydraulic diameters ranging from 1 mm – 4 mm were studied to characterize the influence of tube miniaturization on the flow mechanisms. For each tube under consideration, flow mechanisms were recorded over the entire range of qualities 0 < x < 1, and for five different mass fluxes between 150 kg/m2-s and 750 kg/m2-s. Approximately 50 data points were recorded for each tube to obtain a comprehensive understanding of the effects of geometry, mass flux and quality on the phase-change flow mechanisms. The flow mechanisms were categorized into four different flow regimes: intermittent flow, wavy flow, annular flow, and dispersed flow. In addition, the large amount of data over a wide range of test conditions enabled the delineation of several different flow patterns within each flow regime, which provides a clearer understanding of the different modes of two-phase flow. Transition lines between the respective flow patterns and regimes on these maps were established based on the experimental data. It was found that the intermittent flow regime becomes larger as the tube hydraulic diameter is decreased. Also, the size of the wavy flow regime decreases for the small diameter tubes, and disappears completely for the 1 × 1 mm square tube. These maps and transition lines can be used to predict the flow pattern or regime that will be established for a given mass flux, quality and tube geometry.

Co-Current Air-Water Two Phase Flow Patterns in Horizontal and Vertical Circular Tube Under Various Inlet Conditions

2011 ◽  
Author(s):  
S. Zeguai ◽  
S. Chikh ◽  
O. Rahli ◽  
L. Tadrist
Keyword(s):  
Annular Flow ◽  
Two Phase Flow ◽  
Bubbly Flow ◽  
Flow Patterns ◽  
Phase Flow ◽  
Transition Flow ◽  
Two Phase ◽  
Experimental Apparatus ◽  
Inner Diameter ◽  
Inlet Conditions

An experimental apparatus is setup to analyze a co-current air-water two phase flow in a 3 mm inner diameter tube with horizontal and vertical orientations. Air is axially injected through a nozzle of 260 μm of inner diameter. Air and water flow rates are accurately controlled at the inlet, covering a range of apparent velocities JL = 0.00118 to 0.0786 m/s, JG = 0.002 to 3.538 m/s for the horizontal tube and JL = 0.00078 to 0.0589 m/s, JG = 0.003 to 3.538 m/s for the upward flow. A fast camera with 250 fps is utilized to visualize the flow patterns. The experiments showed that the flow structures are very sensitive to inlet conditions. Within the covered range of velocities, several flow patterns were observed, namely bubbly flow, bubbly-slug transition flow, slug flow, slug-annular transition flow, annular flow, wavy annular flow and annular flow with dry zones. In the bubbly flow regime, a particular bubbly helical flow is observed before the dispersed bubbly flow.

Model of Two-Phase Heterogeneous Mixture Flow in a Microchannel With Incorporated Flow Patterns

2005 ◽  
Author(s):  
Jerry K. Keska
Keyword(s):  
Mathematical Model ◽  
Flow Pattern ◽  
Two Phase Flow ◽  
Full Range ◽  
Flow Patterns ◽  
Calculation Model ◽  
Phase Flow ◽  
Heterogeneous Mixture ◽  
Two Phase ◽  
Mixture Flow

In the two-phase or multiphase flow of such heterogeneous mixture like gas-liquid there is a very complicated and random phenomenon of flow patterns, which needs to be quantitatively and accurately, incorporated. Unfortunately, a model with quantitatively incorporated flow patterns in full range of concentration or method of how to measure flow patterns is not available. Recognizing these challenges this paper will present an approach to incorporate flow pattern phenomenon into the two-phase flow calculation model by (1) developing a mathematical model for pressure losses in two-phase flow based on in-situ parameters, (2) developing and defining a flow pattern coefficient, which incorporates the flow pattern phenomena, and (3) present the developed mathematical model with the incorporation of flow patterns, which demonstrated significant increase of accuracy of calculations based on conducted experimental research on air-water two-phase mixture flow in a horizontal square microchannel.

Incorporated Flow Patterns Into a Model of Two-Phase Heterogeneous Mixture Flow in Microchannels

2006 ◽  
Author(s):  
Jerry K. Keska
Keyword(s):  
Mathematical Model ◽  
Flow Pattern ◽  
Two Phase Flow ◽  
Full Range ◽  
Flow Patterns ◽  
Phase Flow ◽  
Heterogeneous Mixture ◽  
Two Phase ◽  
Mixture Flow ◽  
Pressure Losses

In the two-phase or multiphase flow of such heterogeneous mixture like gas-liquid many more independent parameters are involved, thereby making this process more complicated and less transparent for understanding, mathematical modeling and simulating or calculating of such parameter like the length pressure gradient. In two-phase flow, there is a very complicated and random phenomenon of flow patterns, which needs to be quantitatively and accurately incorporated. Unfortunately, nowadays, a method of how to measure flow patterns is not available. And, also there is a need for mathematical models with quantitatively incorporated flow patterns in full range of flow. It is understandable that in all such cases any reasonable attempt to define and incorporate quantitatively this phenomenon in mathematical model will be beneficial. Recognizing these challenges this paper will present an approach to incorporate flow pattern phenomenon into the two-phase flow model by (1) developing a mathematical model for pressure losses in two-phase flow based on in-situ parameters, (2) developing and defining a flow pattern coefficient, which incorporates the flow pattern phenomena, and (3) present the developed mathematical model with the incorporation of flow patterns, which demonstrated significant increase of accuracy of calculations based on conducted experimental research on air-water twophase mixture flow in a horizontal square microchannel.

Pressure Gradient Prediction in Particle-Liquid Two-Phase Flow

2008 ◽  
Author(s):  
Hikmet S¸. Aybar ◽  
Mohsen Sharifpur ◽  
Roozbeh Vaziri
Keyword(s):  
Porous Media ◽  
Pressure Gradient ◽  
Two Phase Flow ◽  
Industrial Applications ◽  
Experimental Results ◽  
Phase Flow ◽  
Empirical Expression ◽  
Two Phase ◽  
Essential Step ◽  
Experimental Apparatus

The prediction of pressure gradient in two-phase flows is an essential step in the design of a variety of industrial applications. In this study, it is developed the idea that porous media could be a particle-liquid two-phase flow with saturation of the particles. Thus, by setting up an experimental apparatus, it is investigated the behavior of particle-liquid two-phase flow in the cases of dilution of the particles to rich porous media. By using the experimental results an empirical expression is offered for the prediction of pressure gradient of particle-liquid two-phase flow.

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