scholarly journals Modeling Multiphase Effects in CO2 Compressors at Subcritical Inlet Conditions

2019 ◽  
Vol 141 (8) ◽  
Author(s):  
Ashvin Hosangadi ◽  
Zisen Liu ◽  
Timothy Weathers ◽  
Vineet Ahuja ◽  
Judy Busby
Keyword(s):  
Test Data ◽  
Elevated Temperatures ◽  
Wilson Line ◽  
Saturation Pressure ◽  
Flow Coefficient ◽  
Pure Liquid ◽  
Two Phase ◽  
Pressure Profiles ◽  
Wide Range ◽  
Inlet Conditions

An advanced numerical framework to model CO2 compressors over a wide range of subcritical conditions is presented in this paper. Thermodynamic and transport properties are obtained through a table look-up procedure with specialized features for subcritical conditions. Phase change is triggered by the difference between the local values of pressure and saturation pressure, and both vaporization and condensation can be modeled. Rigorous validation of the framework is presented for condensation in high pressure CO2 using test data in a De Laval nozzle. The comparisons between computations and test data include: condensation onset locations, Wilson line, and nozzle pressure profiles as a function of inlet pressures. The framework is applied to the Sandia compressor that has been modeled over broad range of conditions spanning the saturation dome including: near critical inlet conditions (305.4 K, and 7.843 MPa), pure liquid inlet conditions (at 295 K), pure vapor inlet conditions (at 302 K), and two-phase inlet conditions (at 290 K). Multiphase effects ranging from cavitation at the liquid line to condensation at the vapor line have been simulated. The role of real fluid effects in enhancing multiphase effects at elevated temperatures closer to the critical point has been identified. The performance of the compressor has been compared with test data; the computational fluid dynamics (CFD) results also show that the head-flow coefficient curve collapses with relatively minor scatter, similar to the test data, when the flow coefficient is defined on the impeller exit meridional velocity.

CFD Prediction of Safety Valve Disc Forces Under Two Phase Flow Conditions

2018 ◽  
Author(s):  
William Dempster ◽  
Moftah Alshaikh
Keyword(s):  
Two Phase Flow ◽  
Safety Valve ◽  
Phase Flow ◽  
Complex Flow ◽  
Two Phase ◽  
Wide Range ◽  
Valve Disc ◽  
Valve Dynamics ◽  
Inlet Conditions ◽  
Industrial Refrigeration

At present there are very few published works on prediction based methods to establish the forces that act on safety valves during two-phase operation. This means that the valve dynamics and resulting opening and closure are uncertain for a wide range of complex flow applications. This paper describes a study whereby a safety valve, primarily developed for the industrial refrigeration sector is investigated for a range of steady state high gas mass fraction inlet conditions, (gas mass quality 1-0.2) and the disc force characteristics measured for valve choked conditions. The highly compressible two phase flow processes are modelled using an Euler–Euler two fluid CFD approach and the results compared with the experiments. Results indicate that CFD approaches can reasonably capture the key processes but deficiencies exist due to the prediction of two phase built up backpressure in the valve. The methods and data trends are discussed to show the effectiveness of current modelling approaches.

Assessment of Dimensionless Correlations for Prediction of Refrigerant Mass Flow Rate Through Capillary Tubes — A Review

2017 ◽  
Vol 25 (04) ◽  
pp. 1730004 ◽  
Author(s):  
Mehdi Rasti ◽  
Ji Hwan Jeong
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Capillary Tube ◽  
Capillary Tubes ◽  
Two Phase ◽  
Comprehensive Review ◽  
Wide Range ◽  
Inlet Conditions ◽  
Dimensionless Correlations

Capillary tubes are widely used as expansion devices in small-capacity refrigeration systems. Since the refrigerant flow through the capillary tubes is complex, many researchers presented empirical dimensionless correlations to predict the refrigerant mass flow rate. A comprehensive review of the dimensionless correlations for the prediction of refrigerants mass flow rate through straight and coiled capillary tubes depending on their geometry and adiabatic or diabatic capillary tubes depending on the flow configurations has been discussed. A comprehensive review shows that most of previous dimensionless correlations have problems such as discontinuity at the saturated lines or ability to predict the refrigerant mass flow rate only for the capillary tube subcooled inlet condition. The correlations suggested by Rasti et al. and Rasti and Jeong appeared to be general and continuous and these correlations can be used to predict the refrigerant mass flow rate through all the types of capillary tubes with wide range of capillary tube inlet conditions including subcooled liquid, two-phase mixture, and superheated vapor conditions.

Experimental and Numerical Investigation on the Evaporation of Shear-Driven Multi-Component Liquid Wall Films

2000 ◽  
Author(s):  
M. Gerendas ◽  
S. Wittig
Keyword(s):  
Flow Rate ◽  
Liquid Flow ◽  
Liquid Flow Rate ◽  
Inlet Temperature ◽  
Two Phase ◽  
Component Mixture ◽  
Wall Functions ◽  
Hot Air ◽  
Wide Range ◽  
Inlet Conditions

The presented work is concerned with two-phase flows similar to those in prefilming airblast atomizers and combustors employing film vaporization. Correlations for the multi-component mixture properties and models for the calculations of the multi-component evaporation were implemented in a well tested elliptic finite-volume code GAP-2D (Wittig et al., 1992) utilizing time-averaged quantities, k,ε-turbulence model, wall functions, and curve-linear coordinates in the gas phase, adiabatic or diabatic conditions at the film plate, partially turbulent velocity profile, uniform temperature and rapid mixing approach in the wavy film. This new code GAP-2K was tested for stability, precision, and grid independence of the results by applying it to a turbulent hot air flow over a two-component liquid film, a mixture of water and ethanol in different concentrations. Both simulations and experiments, were carried out over a wide range of inlet conditions, such as inlet pressure (1–2.6 bar), inlet temperature (298–573 K), inlet air velocity (30–120 m/s), initial liquid flow rate (0.3–1.2 cm2/s), and initial ethanol concentration (20–75 % mass). Profiles of temperature-, gas velocity, and concentration of the evaporating component normal to the film, and the development of the film temperature, the static pressure, the liquid flow rate and the liquid compound along the film plate have been measured and compared with the simulation showing a good match.

Simple Measurements of Toughness and Crack Formation in Several Intermetallic-Matrix Composite Systems

1990 ◽  
Vol 194 ◽  
Author(s):  
Robert L. Fleischer
Keyword(s):  
Crack Formation ◽  
Elevated Temperatures ◽  
High Fracture Toughness ◽  
Second Phase ◽  
High Fracture ◽  
Two Phase ◽  
Intermetallic Matrix ◽  
Wide Range ◽  
Intermetallic Matrix Composite ◽  
Correlate Observation

AbstractChisel-and-hammer (C.T.) and microhardness tests have been used to examine trends in toughness and crack formation in several intermetallic-based two-phase equilibrium systems. High fracture toughness, as defined by the chisel test, correlates with the presence of some ductility; and the lack of crack formation, or its limitation by a second phase in the microstructure, are prerequisites for fracture resistance. Equilibrium systems have desirable stability for use at elevated temperatures. Comparison of Tbd and C.T. is now possible for a wide range of intermetallics. Intuition suggests that Tbd and C.T. would anti-correlate. Observation, however, contradicts that hypothesis. There are significant numbers of alloys with low Tbd and low C.T. and with high Tbd and high C.T. Possible explanations are noted. Systems that have been studied include Al-Ru with Sc additions, Be-Ti, Be-Zr, Cr-Ti, with Al, Nb and Zr, Ge-Ti, Ir-Nb with Co, Fe, Ni, and V, and Ru-Ta with Co and Fe. Compositional effects on chisel toughness, hardness-vs-temperature, and crack information are presented.

Experimental and Numerical Investigation on the Evaporation of Shear-Driven Multicomponent Liquid Wall Films

2001 ◽  
Vol 123 (3) ◽  
pp. 580-588 ◽  
Author(s):  
M. Gerendas ◽  
S. Wittig
Keyword(s):  
Flow Rate ◽  
Liquid Flow ◽  
Gas Turbines ◽  
Liquid Flow Rate ◽  
Liquid Films ◽  
Inlet Temperature ◽  
Two Phase ◽  
Wall Functions ◽  
Wide Range ◽  
Inlet Conditions

The presented work is concerned with two-phase flows similar to those in prefilming airblast atomizers and combustors employing film vaporization. Correlations for the multicomponent mixture properties and models for the calculations of the multicomponent evaporation were implemented in a well tested elliptic finite-volume code GAP-2D (S. Wittig et al., 1992, “Motion and Evaporation of Shear-Driven Liquid Films in Turbulent Gas,” ASME J. Eng. Gas Turbines Power 114, pp. 395–400) utilizing time-averaged quantities, k,ε turbulence model, wall functions, and curve-linear coordinates in the gas phase, adiabatic or diabatic conditions at the film plate, partially turbulent velocity profile, uniform temperature, and a rapid mixing approach in the wavy film. This new code GAP-2K was tested for stability, precision, and grid independence of the results by applying it to a turbulent hot air flow over a two-component liquid film, a mixture of water and ethanol in different concentrations. Both simulations and experiments were carried out over a wide range of inlet conditions, such as inlet pressure (1–2.6 bar), inlet temperature (298–573 K), inlet air velocity (30–120 m/s), initial liquid flow rate (0.3–1.2 cm2/s), and initial ethanol concentration (20–75 percent mass). Profiles of temperature, gas velocity, and concentration of the evaporating component normal to the film, and the development of the film temperature, the static pressure, the liquid flow rate, and the liquid compound along the film plate have been measured and compared with the simulation, showing a good match.

Modeling and Numerical Prediction of Flow Boiling in a Thin Geometry

2004 ◽  
Vol 126 (1) ◽  
pp. 22-33 ◽  
Author(s):  
Ranganathan Kumar ◽  
Charles C. Maneri ◽  
T. Darton Strayer
Keyword(s):  
Flow Boiling ◽  
Bubbly Flow ◽  
Three Dimensional ◽  
Companion Paper ◽  
Two Phase ◽  
Void Fractions ◽  
Field Modeling ◽  
System Pressure ◽  
Wide Range ◽  
Inlet Conditions

An analysis capability to examine the two-phase bubbly flow in high pressure boiling systems has been developed. The models have been adapted from the literature for a narrow high aspect ratio geometry using the measurements obtained in a companion paper. Three-dimensional computational results have been compared with cross-section averaged and line-averaged void fractions measured with a gamma densitometer, and local void fraction measured with a hot-film anemometer. These comparisons have been made over a wide range of flow inlet conditions, wall heating and system pressure. Comparisons are found to be good when the flow is bubbly, but at high void fractions, where the flow is churn-turbulent or annular, the two-field modeling approach does not perform adequately. This result emphasizes the need for multiple field modeling.

Experimental Analysis of a Two Phase Air-Water Flow in a Tube of Small Size Diameter Under Various Inlet Conditions

2010 ◽  
Author(s):  
S. Zeguai ◽  
S. Chikh ◽  
O. Rahli ◽  
L. Tadrist
Keyword(s):  
Water Flow ◽  
Bubbly Flow ◽  
Water Flow Rate ◽  
Flow Regimes ◽  
Vertical Tube ◽  
Two Phase ◽  
Wide Range ◽  
Experimental Apparatus ◽  
Inner Diameter ◽  
Inlet Conditions

An experimental apparatus is setup to analyze a two phase air-water upward flow in a vertical tube with an inner diameter of 3 mm. Air is axially injected through a microduct of 260 μm inner diameter. Various inlet conditions for air pressure and water flow rate are tested covering a wide range of superficial velocities JL = 0.221 to 0.312 m/s and JG = 0.061 to 0.083 m/s for a given position of air injection (x = 8cm). A fast camera with 250 fps is used to visualize different flow regimes. Experiments showed that the flow type is very sensitive to inlet conditions and several flow regimes were observed namely: the bubbly flow, the slug flow and the annular flow.

Mechanical Properties and Dislocation Structure of Single Crystal Cdte Deformed in Compression at 300°C

1976 ◽  
Vol 34 ◽  
pp. 592-593
Author(s):  
Ernest L. Hall ◽  
J. B. Vander Sande
Keyword(s):  
Mechanical Properties ◽  
Single Crystal ◽  
Dislocation Structure ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Strain Curve ◽  
Optical Devices ◽  
Semiconductor Compound ◽  
Wide Range ◽  
Sample Orientation

The present paper describes research on the mechanical properties and related dislocation structure of CdTe, a II-VI semiconductor compound with a wide range of uses in electrical and optical devices. At room temperature CdTe exhibits little plasticity and at the same time relatively low strength and hardness. The mechanical behavior of CdTe was examined at elevated temperatures with the goal of understanding plastic flow in this material and eventually improving the room temperature properties. Several samples of single crystal CdTe of identical size and crystallographic orientation were deformed in compression at 300°C to various levels of total strain. A resolved shear stress vs. compressive glide strain curve (Figure la) was derived from the results of the tests and the knowledge of the sample orientation.

USS TENELON

Alloy Digest ◽  
1975 ◽  
Vol 24 (5) ◽  
Keyword(s):  
Corrosion Resistance ◽  
Elevated Temperatures ◽  
Stress Rupture ◽  
High Strength ◽  
Heat Treating ◽  
Creep Properties ◽  
United States Steel Corporation ◽  
Excellent Corrosion Resistance ◽  
Wide Range ◽  
Mild Acid

Abstract USS TENELON is a completely austenitic, nickel-free stainless steel with exceptionally high strength which is retained at elevated temperatures. It has excellent corrosion resistance in atmospheric and mild acid exposures and maintains nonmagnetic characteristics even when 60% cold reduced. It also has good stress-rupture and creep properties in the range 1200-1500 F. It has a wide range of applications. This datasheet provides information on composition, physical properties, elasticity, and tensile properties as well as fracture toughness, creep, and fatigue. It also includes information on high temperature performance and corrosion resistance as well as forming, heat treating, machining, joining, and surface treatment. Filing Code: SS-311. Producer or source: United States Steel Corporation.

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