Determination of Two-Phase Flow Void Fraction of R600a in a Horizontal Smooth Tube

2012 ◽  
Author(s):  
Özden Ağra ◽  
Hakan Demir ◽  
Ş. Özgür Atayılmaz ◽  
Ahmet Yurtseven ◽  
A. Selim Dalkılıç ◽  
...  
Keyword(s):  
Neural Network ◽  
Void Fraction ◽  
High Speed ◽  
Saturation Temperature ◽  
Horizontal Tube ◽  
Processing Technique ◽  
Image Processing Technique ◽  
Two Phase ◽  
Void Fractions

In this paper, the void fraction of alternative refrigerant R600a flowing inside horizontal tube is determined by means of an experimental technique, well known correlations in the literature and a generalized neural network analysis. The horizontal tube is made from smooth glass tubing of 4 mm inner diameter. The test runs are done at average saturated condensing temperatures between 30 and 40 °C while the average qualities and the mass fluxes are between 0.45–0.91 and 68.5–138.1 kg m-2s-1 respectively. The flow regime determination inside the tube is performed by means of sight glasses placed at the inlet and outlet sections of the test section, used for in-tube condensation tests, virtually. An image processing technique, performed by means of a high speed camera, is used to determine the void fractions of stratified and annular condensing flow of R600a experimentally. The void fractions are determined using relevant measured data together with 11 different void fraction models and correlations reported in the open literature analytically. Artificial neural network (ANN) analysis is developed to determine the void fractions numerically. For this aim, mass flow rate, average vapor quality, saturation temperature, liquid and vapor densities, liquid and vapor dynamic viscosities and surface tension are selected as the input parameters, while the void fraction is selected as the output. Three-layer network is used for predicting the void fraction. The number of the neurons in the hidden layer was determined by a trial and error process evaluating the performance of the network and standard sensitivity analysis. The measured void fraction values are found to be in good agreement with those from ANN analysis and correlations in the literature. It is also seen that the trained network are more predictive on the determination of void fraction than most of the investigated correlations.

Estimation of Average Void Fraction for Gas-Liquid, Two-Phase Flow in an Industrial Nozzle Assembly Using a Quick-Closing-Valve

2008 ◽  
Author(s):  
Mohammad A. Rahman ◽  
Johana Gomez ◽  
Ted Heidrick ◽  
Brian A. Fleck ◽  
Jennifer McMillan
Keyword(s):  
Void Fraction ◽  
High Speed ◽  
Two Phase Flow ◽  
Video Camera ◽  
Synchronization Error ◽  
Phase Flow ◽  
Closing Time ◽  
Two Phase ◽  
Void Fractions ◽  
Atomization Performance

Experimentally accurate void fraction measurements are a challenge in an air/water, two-phase flows through an industrial nozzle assembly, as a highly non-uniform void fraction exists in the feeding conduit prior to the nozzle. In this study, average void fractions were measured by isolating a section in the feeding conduit of a horizontal nozzle assembly, termed as the quick-closing-valve (QCV) technique. A high-speed video camera was utilized to capture the asynchronization closing time, tac. The average closing time and asynchronization for the pneumatically controlled valves were 200 ms and 2 ms, respectively. Based on the equation of 100umtac (1−α)/αlc, the synchronization error between the two valves was 1.12%, 1.26%, and 1.79% for the 1%, 2% and 4% ALR cases, respectively; here um is the mixture velocity, α is the void faction, and lc is the closing length. Higher synchronization error at 4% ALR occurs due to enhanced momentum in the flow regime. Experimental results indicate that the average α over the 33.4 cm feeding conduit (6.25 mm ID) was 76% (αtheoretical = 75%) for the 2% ALR, and 85% (αtheoretical = 83%) for the 3.3% ALR. In the two-phase, two-component flow the α affects the drop size and stability of the spray produced from an industrial nozzle assembly. Learning from this study will yield insights and conceptual understanding of two-phase flow phenomena in conduit, which would affect stability, pulsation tendency, and possibly atomization performance of the nozzle downstream. Two-phase flow nozzles have wide applications in the industries, e.g. petrochemical, pharmaceutical, and others.

INVESTIGATION ON VOID FRACTION FOR TWO-PHASE FLOW PRESSURE DROP OF EVAPORATIVE R-290 IN HORIZONTAL TUBE

2016 ◽  
Vol 78 (8-4) ◽  
Author(s):  
Agus Sunjarianto Pamitran ◽  
Sentot Novianto ◽  
Normah Mohd-Ghazali ◽  
Nasruddin Nasruddin ◽  
Raldi Koestoer
Keyword(s):  
Pressure Drop ◽  
Void Fraction ◽  
Two Phase Flow ◽  
Flow Boiling ◽  
Homogeneous Model ◽  
Saturation Temperature ◽  
Horizontal Tube ◽  
Phase Flow ◽  
Two Phase ◽  
Experimental Conditions

Two-phase flow boiling pressure drop experiment was conducted to observe its characteristics and to develop a new correlation of void fraction based on the separated model. Investigation is completed on the natural refrigerant R-290 (propane) in a horizontal circular tube with a 7.6 mm inner diameter under experimental conditions of 3.7 to 9.6 °C saturation temperature, 10 to 25 kW/m2 heat flux, and 185 to 445 kg/m2s mass flux. The present experimental data was used to obtain the calculated void fraction which then was compared to the predicted void fraction with 31 existing correlations. A new void fraction correlation for predicting two-phase flow boiling pressure drop, as a function of Reynolds numbers, was proposed. The measured pressure drop was compared to the predicted pressure drop with some existing pressure drop models that use the newly developed void fraction model. The homogeneous model of void fraction showed the best prediction with 2% deviation

Computational Estimation of Bubble Gas Velocity for Slug Flow Pattern in Horizontal Pipes Using Image Processing Technique

2012 ◽  
Author(s):  
María T. Valecillos ◽  
Carlos H. Romero ◽  
María A. Márquez ◽  
Sissi D. Vergara
Keyword(s):  
Image Processing ◽  
Flow Pattern ◽  
Slug Flow ◽  
High Speed ◽  
Processing Technique ◽  
Image Processing Technique ◽  
Gas Velocity ◽  
Two Phase ◽  
Horizontal Pipes ◽  
Computational Estimation

Two-phase slug flow pattern is one of the most common flow patterns present in many industries, therefore its study becomes relevant. The aim of this work was to develop an automated computational program to determine the bubble gas velocity associated to gas-liquid two-phase slug flow by using video digital image processing technique. In order to obtain the images for the analysis, experiments were carried out using a pipe bench for air-water two-phase flow. The experimental facility is located in Simon Bolivar University, in Venezuela. The system has three pipes with different internal diameters and can be rotated around its axis and fixed at any inclination angle from horizontal to vertical flow. The tests were run in a horizontal pipeline of 0.03175m of internal pipe diameter and 8m long. For slug flow visualization a high speed camera Kodak Ektapro 4540mx imager was used. The camera was located in an x/D relation corresponding to 249 from the pipe inlet, ensuring the complete development of the flow. The camera allowed a maximum acquisition velocity of 4500 frames per second. The superficial velocity range was 0.16–1.79m/s and 0.16–1.26m/s for air and water, respectively. To summarize, 165 tests were performed and 1320000 images were analyzed with 20 flow rate combinations. The computational application was validated by comparing it with the velocities measured manually over selected images. Results obtained were compared to several correlations such as Bendiksen [1], Cook & Behnia [2] and Wang et al. [3].

Correlation between Void Fraction and Two-Phase Flow Pattern Air-Water with Low Viscosity in Mini Channel with Slope 30 Degrees

2020 ◽  
Vol 846 ◽  
pp. 289-295
Author(s):  
Sukamta ◽  
Sudarja
Keyword(s):  
Void Fraction ◽  
High Speed ◽  
Two Phase Flow ◽  
Fluid Velocity ◽  
Flow Patterns ◽  
Superficial Velocity ◽  
Working Fluid ◽  
Phase Flow ◽  
Two Phase ◽  
Void Fractions

Two-phase flow has been used in so many industrial processes, such as boilers, reactors, heat exchangers, geothermal and others. Some parameters which need to be studied include flow patterns, void fractions, and pressure changes. Research on void fractions aims to determine the composition of the gas and liquid phases that will affect the nature and value of the flow property. The purpose of this study is to find out the characteristics of the void fraction of various patterns that occurs and to determine the characteristics of the velocity, length, and frequency of bubbly and plug. Data acquisition was used to convert the data from analog to digital so that it can be recorded, stored, processed, and analyzed. High-speed camera Nikon type J4 was used to record the flow. The condition of the study was adiabatic with variation of superficial gas velocity (JG), superficial fluid velocity (JL), and also working fluid. To determine the void fraction by using the digital image processing method. The results of the study found that the flow patterns which occurred in this study were bubbly, plug, annular, slug-annular and churn flows. It also showed that the void fraction value is determined by the superficial velocity of the liquid and air. The higher the superficial velocity of the air, the lower the void fraction value.

Experimental determination of void fraction in surface aeration using image processing technique

2015 ◽  
Vol 29 (6) ◽  
pp. 2391-2400 ◽  
Author(s):  
Amir Mohammadpour ◽  
Mohammad Ali Akhavan-Behabadi ◽  
Masoud Ebrahimzadeh ◽  
Pedram Hanafizadeh ◽  
Mehrdad Raisee
Keyword(s):  
Image Processing ◽  
Experimental Determination ◽  
Void Fraction ◽  
Processing Technique ◽  
Image Processing Technique ◽  
Surface Aeration

Gas Void Fraction Prediction for Air-Water and Air-Oil Two-Phase Flows via Artificial Neural Network

2019 ◽  
Author(s):  
Tiago Ferreira Souza ◽  
Caio Araujo ◽  
Maurício Figueiredo ◽  
FLAVIO SILVA ◽  
Ana Maria Frattini Fileti
Keyword(s):  
Neural Network ◽  
Artificial Neural Network ◽  
Void Fraction ◽  
Two Phase Flows ◽  
Two Phase ◽  
Artificial Neural ◽  
Gas Void Fraction

scholarly journals Determination of cross-sectional void fraction in a two-phase water flow through a PVC pipe

2021 ◽  
Vol 655 (1) ◽  
pp. 012024
Author(s):  
O.H. Ajesi ◽  
M.B. Latif ◽  
S.T. Gbenu ◽  
C. A. Onumejor ◽  
M. K. Fasasi ◽  
...  
Keyword(s):  
Water Flow ◽  
Void Fraction ◽  
Two Phase ◽  
Cross Sectional ◽  
Flow Through ◽  
Pvc Pipe ◽  
Phase Water

Two-Phase Friction Factor Obtained From Various Void Fraction Models During Condensation of R134A in Vertical Downward Flow at High Mass Flux

2008 ◽  
Author(s):  
Ahmet Selim Dalkilic ◽  
Suriyan Laohalertdecha ◽  
Somchai Wongwises
Keyword(s):  
Void Fraction ◽  
Annular Flow ◽  
Smooth Tube ◽  
High Mass ◽  
Two Phase ◽  
Void Fractions ◽  
Mass Fluxes ◽  
Friction Factors ◽  
Flow Void ◽  
Fraction Models

Void fractions are determined in vertical downward annular two-phase flow of R134a inside 8.1 mm i.d. smooth tube. The experiments are done at average saturated condensing temperatures of 40 and 50°C. The average qualities are between 0.84–0.94. The mass fluxes are around 515 kg m−2s−1. The experimental setup is explained elaborately. Comparisons between the void fraction determined from 35 void fraction correlations are done. According to the use of various horizontal and vertical annular flow void fraction models together with the present experimental condensation heat transfer data, similar void fraction results were obtained mostly for the smooth tube. The experimental friction factors obtained from void fraction correlations are compared with the friction factors determined from graphical information provided by Bergelin et. al. Effect of void fraction alteration on the momentum pressure drop is also presented.

scholarly journals Bubble Dynamics in a Two-Phase Bubbly Mixture

2010 ◽  
Author(s):  
Arvind Jayaprakash ◽  
Sowmitra Singh ◽  
Georges Chahine
Keyword(s):  
Void Fraction ◽  
High Speed ◽  
Bubble Dynamics ◽  
Bubble Radius ◽  
Discharge Voltage ◽  
Large Bubble ◽  
Water Mixture ◽  
Two Phase ◽  
Mixture Density ◽  
Bubbly Medium

The dynamics of a primary relatively large bubble in a water mixture including very fine bubbles is investigated experimentally and the results are provided to several parallel on-going analytical and numerical approaches. The main/primary bubble is produced by an underwater spark discharge from two concentric electrodes placed in the bubbly medium, which is generated using electrolysis. A grid of thin perpendicular wires is used to generate bubble distributions of varying intensities. The size of the main bubble is controlled by the discharge voltage, the capacitors size, and the pressure imposed in the container. The size and concentration of the fine bubbles can be controlled by the electrolysis voltage, the length, diameter, and type of the wires, and also by the pressure imposed in the container. This enables parametric study of the factors controlling the dynamics of the primary bubble and development of relationships between the bubble characteristic quantities such as maximum bubble radius and bubble period and the characteristics of the surrounding two-phase medium: micro bubble sizes and void fraction. The dynamics of the main bubble and the mixture is observed using high speed video photography. The void fraction/density of the bubbly mixture in the fluid domain is measured as a function of time and space using image analysis of the high speed movies. The interaction between the primary bubble and the bubbly medium is analyzed using both field pressure measurements and high-speed videography. Parameters such as the primary bubble energy and the bubble mixture density (void fraction) are varied, and their effects studied. The experimental data is then compared to simple compressible equations employed for spherical bubbles including a modified Gilmore Equation. Suggestions for improvement of the modeling are then presented.

Prediction of Pump Performance Under Air-Water Two-Phase Flow Based on a Bubbly Flow Model

1993 ◽  
Vol 115 (4) ◽  
pp. 781-783 ◽  
Author(s):  
Kiyoshi Minemura ◽  
Tomomi Uchiyama
Keyword(s):  
Two Phase Flow ◽  
Bubbly Flow ◽  
Phase Flow ◽  
Centrifugal Pumps ◽  
Flow Conditions ◽  
Two Phase ◽  
Performance Change ◽  
Void Fractions ◽  
Two Phases

This paper is concerned with the determination of the performance change in centrifugal pumps operating under two-phase flow conditions using the velocities and void fractions calculated under the assumption of an inviscid bubbly flow with slippage between the two phases. The estimated changes in the theoretical head are confirmed with experiments within the range of bubbly flow regime.

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