Bounds on Two-Phase Flow: Part II — Void Fraction in Circular Pipes

2005 ◽  
Author(s):  
M. M. Awad ◽  
Y. S. Muzychka
Keyword(s):  
Experimental Data ◽  
Void Fraction ◽  
Mass Flow ◽  
Liquid Fraction ◽  
Published Data ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Rates ◽  
Working Fluids ◽  
Mass Flow Rates

Theoretical and empirical models for the gas void fraction (α) are reviewed. Simple rules are developed for obtaining rational bounds for the void fraction in two-phase flow. The lower bound is based on the separate cylinders formulation for turbulent-turbulent flow that uses the Blasius equation to predict the Fanning friction factor. The upper bound is based on the Butterworth relationship that represents well the Lockhart-Martinelli correlation. These two bounds are reversed in the case of liquid fraction (1−α). The bounds models are verified using published experimental data of void fraction versus mass quality at constant mass flow rate. The published data include different working fluids such as R-12 and R-22 at different pipe diameters, different pressures, and different mass flow rates. It is shown that the published data can be well bounded for a wide range of mass qualities, pipe diameters, pressures and mass flow rates. Further comparisons are made using the published experimental data of void fraction (α) and liquid fraction (1−α) versus the Lockhart-Martinelli parameter (X), for different working fluids such as R-12, R-22 and air-water mixtures.

Two-Phase Flow Behavior in Channels With Sudden Area Change Using Experimental and Computational Approach

2017 ◽  
Author(s):  
Ashish Kotwal ◽  
Che-Hao Yang ◽  
Clement Tang
Keyword(s):  
Experimental Data ◽  
Pressure Drop ◽  
Experimental Analysis ◽  
Single Phase ◽  
Computational Analysis ◽  
Phase Flow ◽  
Single Phase Flow ◽  
Two Phase ◽  
Flow Rates ◽  
Area Change

The current study shows computational and experimental analysis of multiphase flows (gas-liquid two-phase flow) in channels with sudden area change. Four test sections used for sudden contraction and expansion of area in experiments and computational analysis. These are 0.5–0.375, 0.5–0.315, 0.5–0.19, 0.5–0.14, inversely true for expansion channels. Liquid Flow rates ranging from 0.005 kg/s to 0.03 kg/s employed, while gas flow rates ranging from 0.00049 kg/s to 0.029 kg/s implemented. First, single-phase flow consists of only water, and second two-phase Nitrogen-Water mixture flow analyzed experimentally and computationally. For Single-phase flow, two mathematical models used for comparison: the two transport equations k-epsilon turbulence model (K-Epsilon), and the five transport equations Reynolds stress turbulence interaction model (RSM). A Eulerian-Eulerian multiphase approach and the RSM mathematical model developed for two-phase gas-liquid flows based on current experimental data. As area changes, the pressure drop observed, which is directly proportional to the Reynolds number. The computational analysis can show precise prediction and a good agreement with experimental data when area ratio and pressure differences are smaller for laminar and turbulent flows in circular geometries. During two-phase flows, the pressure drop generated shows reasonable dependence on void fraction parameter, regardless of numerical analysis and experimental analysis.

Numerical Analysis of the Flow Inside a Centrifugal Compressor’s Vaneless Diffuser and Volute

2001 ◽  
Author(s):  
Hooman Rezaei ◽  
Abraham Engeda ◽  
Paul Haley
Keyword(s):  
Experimental Data ◽  
Numerical Analysis ◽  
Mass Flow ◽  
Operating Conditions ◽  
Vaneless Diffuser ◽  
Flow Angle ◽  
Flow Rates ◽  
Mass Flow Rates ◽  
Minimum Medium ◽  
Good Agreement

Abstract The objective of this work was to perform numerical analysis of the flow inside a modified single stage CVHF 1280 Trane centrifugal compressor’s vaneless diffuser and volute. Gambit was utilized to read the casing geometry and generating the vaneless diffuser. An unstructured mesh was generated for the path from vaneless diffuser inlet to conic diffuser outlet. At the same time a meanline analysis was performed corresponding to speeds and mass flow rates of the experimental data in order to obtain the absolute velocity and flow angle leaving the impeller for those operating conditions. These values and experimental data were used as inlet and outlet boundary conditions for the simulations. Simulations were performed in Fluent 5.0 for three speeds of 2000, 3000 and 3497 RPM and mass flow rates of minimum, medium and maximum. Results are in good agreement with the experimental ones and present the flow structures inside the vaneless diffuser and volute.

scholarly journals Pressure Signal Analysis for the Characterization of High-Viscosity Two-Phase Flows in Horizontal Pipes

2020 ◽  
Vol 8 (12) ◽  
pp. 1000
Author(s):  
Lizeth Torres ◽  
José Noguera ◽  
José Enrique Guzmán-Vázquez ◽  
Jonathan Hernández ◽  
Marco Sanjuan ◽  
...  
Keyword(s):  
Mass Flow ◽  
Two Phase Flow ◽  
High Viscosity ◽  
Flow Rate Ratio ◽  
Phase Flow ◽  
Two Phase ◽  
Local Flow ◽  
Horizontal Pipes ◽  
Pressure Time ◽  
Mass Flow Rates

We study a high-viscosity two-phase flow through an analysis of the corresponding pressure signals. In particular, we investigate the flow of a glycerin–air mixture moving through a horizontal pipeline with a U-section installed midway along the pipe. Different combinations of liquid and air mass flow rates are experimentally tested. Then, we examine the moments of the statistical distributions obtained from the resulting pressure time series, in order to highlight the significant dynamical traits of the flow. Finally, we propose a novel correlation with two dimensionless parameters: the Euler number and a mass-flow-rate ratio to predict the pressure gradient in high-viscosity two-phase flow. Distinctive variations of the pressure gradients are observed in each section of the pipeline, which suggest that the local flow dynamics must not be disregarded in favor of global considerations.

An Experimental Study of the Flow of R-407C in an Adiabatic Spiral Capillary Tube

2009 ◽  
Vol 1 (4) ◽  
Author(s):  
M. K. Mittal ◽  
R. Kumar ◽  
A. Gupta
Keyword(s):  
Experimental Data ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Capillary Tube ◽  
Flow Characteristics ◽  
Flow Rates ◽  
Tube Test ◽  
Mass Flow Rates ◽  
R 134A

The objective of this study is to investigate the effect of coiling on the flow characteristics of R-407C in an adiabatic spiral capillary tube. The characteristic coiling parameter for a spiral capillary tube is the coil pitch; hence, the effect of the coil pitch on the mass flow rate of R-407C was studied on several capillary tube test sections. It was observed that the coiling of the capillary tube significantly reduced the mass flow rate of R-407C in the adiabatic spiral capillary tube. In order to quantify the effect of coiling, the experiments were also conducted for straight a capillary tube, and it was observed that the coiling of the capillary tube reduced the mass flow rate in the spiral tube in the range of 9–18% as compared with that in the straight capillary tube. A generalized nondimensional correlation for the prediction of the mass flow rates of various refrigerants was developed for the straight capillary tube on the basis of the experimental data of R-407C of the present study, and the data of R-134a, R-22, and R-410A measured by other researchers. Additionally, a refrigerant-specific correlation for the spiral capillary was also proposed on the basis of the experimental data of R-407C of the present study.

scholarly journals Validation of NEPTUNE-CFD Two-Phase Flow Models Using Experimental Data

2014 ◽  
Vol 2014 ◽  
pp. 1-19 ◽  
Author(s):  
Jorge Pérez Mañes ◽  
Victor Hugo Sánchez Espinoza ◽  
Sergio Chiva Vicent ◽  
Michael Böttcher ◽  
Robert Stieglitz
Keyword(s):  
Experimental Data ◽  
Void Fraction ◽  
Two Phase Flow ◽  
Model Parameters ◽  
Phase Flow ◽  
Cfd Model ◽  
Two Phase ◽  
Flow Models ◽  
Phase Models ◽  
Good Agreement

This paper deals with the validation of the two-phase flow models of the CFD code NEPTUNEC-CFD using experimental data provided by the OECD BWR BFBT and PSBT Benchmark. Since the two-phase models of CFD codes are extensively being improved, the validation is a key step for the acceptability of such codes. The validation work is performed in the frame of the European NURISP Project and it was focused on the steady state and transient void fraction tests. The influence of different NEPTUNE-CFD model parameters on the void fraction prediction is investigated and discussed in detail. Due to the coupling of heat conduction solver SYRTHES with NEPTUNE-CFD, the description of the coupled fluid dynamics and heat transfer between the fuel rod and the fluid is improved significantly. The averaged void fraction predicted by NEPTUNE-CFD for selected PSBT and BFBT tests is in good agreement with the experimental data. Finally, areas for future improvements of the NEPTUNE-CFD code were identified, too.

Empirical Correlations for Sizing Adiabatic Capillary Tube Using LPG as Refrigerant in Split-Type Air-Conditioner

2014 ◽  
Vol 493 ◽  
pp. 99-104
Author(s):  
Shodiya Sulaimon ◽  
Azhar Abdul Aziz ◽  
Amer Nordin Darus ◽  
Henry Nasution
Keyword(s):  
Experimental Data ◽  
Mass Flow ◽  
Capillary Tube ◽  
Air Conditioner ◽  
Capillary Tubes ◽  
Two Phase ◽  
Design And Optimization ◽  
Mass Flow Rates ◽  
Inner Diameter ◽  
Vapour Compression

This paper presents correlations for sizing adiabatic capillary tubes which serves as an expansion device in split-type air-conditioner with LPG, novel hydrocarbon (HC) mixtures of butane (HC600) and propane (HC290) as refrigerant. A homogenous two-phase flow model developed by the authors and also experimental investigation of the Liquified Petroluem Gas (LPG) refrigerant flow in adiabatic capillary tubes were used in this study. The theoretical model was used to assess various percentage compositions of these HC mixtures and validated with the experimental data. For each HC refrigerant mixture, correlations for sizing adiabatic capillary tube which contains the relevant factors, viz. capillary tube inner diameter, inlet pressure, refrigerant mass flow rate, capillary tube surface roughness and capillary tube inlet subcooling was developed. The proposed correlations were compared with the authors measured data and found to be in good agreement. Further validation was made by comparing the mass flow rates predictions of the correlations with experimental data of previous studies and found that these correlations are consistent. The correlations can be used in small vapour compression refrigeration systems working with the HC refrigerant mixtures for practical design and optimization.

Modelisation and Experimentations on a Steam Injector

2002 ◽  
Author(s):  
Frabrice Durand ◽  
Jean-Marc Dorey ◽  
Jean Fabre
Keyword(s):  
Void Fraction ◽  
Simplified Model ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Rates ◽  
Outlet Pressure ◽  
Mixing Chamber ◽  
Flow Processes ◽  
Condensation Shock ◽  
Feeding Pressure

A simplified model is proposed to predict the flow in a Steam Injector (SI), based on the splitting in successive two phase flow processes. SI experimentations have been carried out including pressure and void fraction measurements. The results show that the model provides good values of flow rates and pressures inside the device and describes well its behavior. It will have to be enriched with dissipative processes, mainly friction in the mixing chamber and dissipation in the condensation shock in order to achieve the prediction of the outlet pressure that can reach more than 4 or 5 times the steam feeding pressure.

Simulations of Waste Heat Recovery System Using R123 and R245fa for Heavy-Duty Diesel Engines

2013 ◽  
Vol 805-806 ◽  
pp. 1827-1835 ◽  
Author(s):  
Ming Shan Wei ◽  
Lei Shi ◽  
Chao Chen Ma ◽  
Danish Syed Noman
Keyword(s):  
Mass Flow ◽  
Thermal Efficiency ◽  
Waste Heat ◽  
Rankine Cycle ◽  
Heavy Duty ◽  
Engine Exhaust ◽  
Flow Rates ◽  
Working Fluids ◽  
Mass Flow Rates ◽  
Heavy Duty Diesel

To improve fuel economy, an Organic Rankine Cycle (ORC) system is proposed to recover waste heat from heavy-duty diesel engines. R123 and R245fa were selected as working fluids. Extensive numerical simulations were conducted to find thermal efficiency of the system under different evaporation pressures, mass flow rates of working fluids and temperature of engine exhaust gases. Results show that the system thermal efficiency was increased with the increase in evaporation pressure for both R123 and R245fa. Efficiency of R123 system was found to be greater than that of R245fa system. For Rankine cycle with both R123 and R245fa, mass flow rate range varied with the evaporation pressure. Limited by evaporation rates and thermal decomposition of the working fluid, the range of mass flow rates in R245fa system was narrower than the R123 system. The thermal efficiency with different temperatures of engine exhaust gases was similar under the fixed evaporation pressure.

Bounds on Two-Phase Frictional Pressure Gradient in Minichannels and Microchannels

2006 ◽  
Author(s):  
M. M. Awad ◽  
Y. S. Muzychka
Keyword(s):  
Laminar Flow ◽  
Pressure Gradient ◽  
Flow Model ◽  
Narrow Channel ◽  
Published Data ◽  
Phase Flow ◽  
Water Mixture ◽  
Two Phase ◽  
Working Fluids ◽  
Simple Rules

Simple rules are developed for obtaining rational bounds for two-phase frictional pressure gradient in minichannels and microchannels. The lower bound is based on Ali et al. correlation for laminar-laminar flow. This correlation is based on modification of simplified stratified flow model derived from the theoretical approach of Taitel and Dukler for the case of two-phase flow in a narrow channel. The upper bound is based on Chisholm correlation for laminar-laminar flow. The model is verified using published experimental data of two-phase frictional pressure gradient in circular and non-circular shapes. The published data include different working fluids such as air-water mixture and nitrogen-water mixture, and different channel diameters. The bounds models are also presented in a dimensionless form as two-phase frictional multiplier (φl and φg) versus Lockhart-Martinelli parameter (X) for different working fluids such as air-water mixture and nitrogen-water mixture. It is shown that the published data can be well bounded.

Sign in / Sign up

Export Citation Format

Share Document