Characteristics of the Hydrodynamic Coefficient for Flow of a Steam-Water Mixture in a Pebble Bed

2006 ◽  
Vol 129 (9) ◽  
pp. 1291-1294 ◽  
Author(s):  
Alexandr A. Avdeev ◽  
Boris F. Balunov ◽  
Rostislav A. Rybin ◽  
Ruslan I. Soviev ◽  
Yuri B. Zudin
Keyword(s):  
Water Flow ◽  
Mass Flow ◽  
Pressure Loss ◽  
Single Phase ◽  
Water Mixture ◽  
Pebble Bed ◽  
Hydrodynamic Coefficient ◽  
Flow Rates ◽  
Wide Range ◽  
Mass Flow Rates

Pressure loss for flow of a steam-water mixture in a pebble bed is experimentally investigated (the first stage of the study was described in Avdeev, et al., 2003 [High Temp., 41, pp. 371–383]). The measurements of the care performed within the wide range of regime parameters: pressures of 0.9-15.6MPa, mass-flow rates of 107-770kg∕(m2s) and steam quality of 0–0.49. The experimental data for the pressure loss of single-phase air and water flows were used as reference data. The final results are represented in the form of the ratio of the pressure loss for the steam-water flow to that for the single-phase water flow at identical mass-flow rates.

scholarly journals Numerical Investigation of Mixing Characteristic for CH4/Air in Rotating Detonation Combustor

2020 ◽  
Vol 10 (4) ◽  
pp. 1298
Author(s):  
Shan Jin ◽  
Qingyang Meng ◽  
Zhiming Li ◽  
Ningbo Zhao ◽  
Hongtao Zheng ◽  
...  
Keyword(s):  
Mass Flow ◽  
Flow Rate ◽  
Pressure Loss ◽  
Equivalence Ratio ◽  
Numerical Study ◽  
Ignition Energy ◽  
Flow Rates ◽  
Mass Flow Rates ◽  
Critical Ignition ◽  
Rotating Detonation

The mixing process of fuel and oxidizer is a very critical factor affecting the real operating performance of non-premixed rotating detonation combustor. In this paper, a two-dimensional numerical study is carried out to investigate the flow and mixing characteristics of CH4/air in combustor with different injection structures. On this basis, the effect of CH4/air mixing on the critical ignition energy for forming detonation is theoretically analyzed in detail. The numerical results indicate that injection strategies of CH4 and air can obviously affect the flow filed characteristic, pressure loss, mixing uniformity and local equivalence ratio in combustor, which further affect the critical ignition energy for forming detonation. In the study for three different mass flow rates (the mass flow rates of air are 12.01 kg/s,8.58 kg/s and 1.72 kg/s, respectively), when air is radially injected into combustor (fuel/air are injected perpendicular to each other), although the mixing quality of CH4 and air is improved, the total pressure loss is also increased. In addition, the comparative analysis also shows that the increase of mass flow rate of CH4/air can decrease the difference of the critical ignition energy for forming detonation at a constant total equivalence ratio. The ignition energy decreases with the decrease of the total flow rate and then increases gradually.

scholarly journals Verification and Improving the Heat Transfer Model in Radiators in the Wide Change Operating Parameters

Energies ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6543
Author(s):  
Mieczysław Dzierzgowski
Keyword(s):  
Heat Transfer ◽  
Mass Flow ◽  
Water Mass ◽  
Heat Transfer Model ◽  
Operating Conditions ◽  
Transfer Model ◽  
Flow Rates ◽  
Wide Range ◽  
Different Types ◽  
Mass Flow Rates

Laboratory measurements and analyses conducted in a wide range of changes of water temperature and mass flow rate for different types of radiators allowed to provides limitations and assessment of the current radiators heat transfer model according to EN 442. The inaccuracy to determinate the radiator heat output according to EN 442, in case of low water mass flow rates may achieve up to 22.3% A revised New Extended Heat Transfer Model in Radiators NEHTMiRmd is general and suitable for different types of radiators both new radiators and radiators existing after a certain period of operation is presented. The NEHTMiRmd with very high accuracy describes the heat transfer processes not only in the nominal conditions—in which the radiators are designed, but what is particularly important also in operating conditions when the radiators water mass flow differ significantly from the nominal value and at the same time the supply temperature changes in the whole range radiators operating during the heating season. In order to prove that the presented new model NEHTMiRmd is general, the article presents numerous calculation examples for various types of radiators currently used. Achieved the high compatibility of the results of the simulation calculations with the measurement results for different types of radiators: iron elements (not ribbed), plate radiators (medium degree ribbed), convectors (high degree ribbed) in a very wide range of changes in the water mass flow rates and the supply temperature indicates that a verified NEHTMiRmd can also be used in designing and simulating calculations of the central heating installations, for the rational conversion of existing installations and district heating systems into low temperature energy efficient systems as well as to directly determine the actual energy efficiency, also to improve the indications of the heat cost allocators. In addition, it may form the basis for the future modification of the European Standards for radiator testing.

scholarly journals Computational study of a radial flow turbine operates under various pulsating flow shapes and amplitudes

2021 ◽  
pp. 1-24
Author(s):  
Ahmed Rezk ◽  
Sidharath Sharma ◽  
S.M. Barrans ◽  
Abul Kalam Hossain ◽  
P. Samuel Lee ◽  
...  
Keyword(s):  
Mass Flow ◽  
Radial Flow ◽  
Pulsating Flow ◽  
Gradual Change ◽  
Maximum Mass ◽  
Flow Rates ◽  
Flow Accumulation ◽  
Wide Range ◽  
Mass Flow Rates ◽  
The Impact

Abstract Radial flow turbines are extensively used in turbocharging technology due to their unique capability of handling a wide range of exhaust gas flow. The pulsating flow nature of the internal combustion engine exhaust gases causes unsteady operation of the turbine stage. This paper presents the impact of the pulsating flow of various characteristics on the performance of a radial flow turbine. A three-dimensional computational fluid dynamic model was coupled with a one-dimensional engine model to study the realistic pulsating flow. Applying square wave pulsating flow showed the highest degree of unsteadiness corresponding to 92.6% maximum mass flow accumulation due to the consecutive sudden changes of the mass flow rates over the entire pulse. Although saw-tooth showed a maximum mass flow accumulation value of 88.9%, the mass flow rates entailed gradual change resulted in the least overall mass flow accumulation over the entire pulse. These two extremes constrained the anticipated performance of the radial flow turbine operates under realistic pulsating flow. Such constraints could develop an operating envelop to predict the performance and optimize radial flow turbines' power extraction under pulsating flow conditions.

scholarly journals Statistical Simulation of Non-Circular Cross Section Poiseuille Flows

2003 ◽  
Author(s):  
Jian-Zheng Jiang ◽  
Ching Shen ◽  
Jing Fan
Keyword(s):  
Mass Flow ◽  
Cross Sections ◽  
Lateral Wall ◽  
Physical Parameters ◽  
Height Ratio ◽  
Dsmc Method ◽  
Flow Rates ◽  
Wide Range ◽  
Mass Flow Rates ◽  
Poiseuille Flows

This paper investigates the Poiseuille flows for rectangular, regular hexagonal, and semicircular cross sections in transition regime using particle approaches, namely the direct simulation Monte Carlo (DSMC) method and the information preservation (IP) method. The DSMC and IP results compare well with each other, while the IP method is much more computationally efficient than the DSMC method. The mass flow rates given by IP and DSMC are in agreement with the BGK solutions of Hasegawa and Sone. For rectangular cross sections in the wide range of the width-to-height ratio, the simulation results of the mass flow rates and the velocity profiles along the midperpendicular line have been given for both methods to estimate the lateral wall influence. For the physical quantities, such as the mass flow rate, which are influenced by the whole field, the lateral wall influence must be considered even for width-to-height ratio as large as 10. And for the physical parameters, such as the maximum velocity and the velocity profile along the midperpendicular line, the lateral wall influence can be negligible if the width-to-height ratio is bigger than 5.

Utilization of Gas-Liquid Cylindrical Cyclone (GLCC©) Compact Separator for Solids Removal—Part II: Operational Envelope for Carry-Over

2009 ◽  
Author(s):  
S. Omarov ◽  
L. Gomez ◽  
S. Wang ◽  
R. Mohan ◽  
O. Shoham ◽  
...  
Keyword(s):  
Experimental Data ◽  
Mass Flow ◽  
Liquid Velocity ◽  
Solid Mass ◽  
Efficient Operation ◽  
Flow Rates ◽  
Wide Range ◽  
Mass Flow Rates ◽  
Carry Over ◽  
Operational Envelope

The operational envelope for particle (solid and liquid) carry-over (OPEN-CO) in the GLCC© has been studied experimentally and theoretically. The experimental data were acquired for a wide range of flow conditions, including: inlet superficial gas and liquid velocities between 15–35 ft/s and 0.1–1.2 ft/s, respectively, solid particle sizes of 5, 25 and 50 microns, and solid mass flow rates between 6.61lbm/min and 15.43 lbm/min. An uncertainty analysis of the experimental data revealed uncertainties less than 1% and less that 8.5% for the superficial liquid velocity and the superficial gas velocity measurements, respectively. Results from the experimental data show that as the density of the slurry increases (higher solid mass flow rates), the OPEN-CO shifts up. A mechanistic model was developed for the prediction of OPEN-CO, based on particle trajectory. The model assumes that the particle (liquid and solid) density is the same as the slurry density. Model predictions agree well with the experimental data. The developed model can be used for design and efficient operation of the GLCC© for gas-liquid-solid flow (gas slurry separation).

Radiation Hydrodynamics of Accreting Magnetic White Dwarfs

1996 ◽  
Vol 158 ◽  
pp. 199-202 ◽  
Author(s):  
K. Beuermann ◽  
U. Woelk
Keyword(s):  
Mass Flow ◽  
White Dwarfs ◽  
Radiation Hydrodynamics ◽  
Hydrodynamic Equations ◽  
Flow Rates ◽  
One Dimensional ◽  
Cyclotron Radiation ◽  
Wide Range ◽  
Mass Flow Rates ◽  
Two Fluid

AbstractWe solved the stationary one-dimensional two-fluid radiation hydrodynamic equations including cyclotron radiation for a wide range of mass flow rates. Here, we discuss the implications for accretion phenomena on the white dwarfs in AM Her binaries.

scholarly journals Theoretical and Numerical Study of Heat Transfer Deterioration in High Performance Light Water Reactor

2008 ◽  
Vol 2008 ◽  
pp. 1-5 ◽  
Author(s):  
David Palko ◽  
Henryk Anglart
Keyword(s):  
Heat Transfer ◽  
Water Flow ◽  
Mass Flow ◽  
High Performance ◽  
Stokes Equations ◽  
Numerical Study ◽  
International Association ◽  
Flow Rates ◽  
Heat Transfer Deterioration ◽  
Mass Flow Rates

A numerical investigation of the heat transfer deterioration (HTD) phenomena is performed using the low-Re k-ωturbulence model. Steady-state Reynolds-averaged Navier-Stokes equations are solved together with equations for the transport of enthalpy and turbulence. Equations are solved for the supercritical water flow at different pressures, using water properties from the standard IAPWS (International Association for the Properties of Water and Steam) tables. All cases are extensively validated against experimental data. The influence of buoyancy on the HTD is demonstrated for different mass flow rates in the heated pipes. Numerical results prove that the RANS low-Re turbulence modeling approach is fully capable of simulating the heat transfer in pipes with the water flow at supercritical pressures. A study of buoyancy influence shows that for the low-mass flow rates of coolant, the influence of buoyancy forces on the heat transfer in heated pipes is significant. For the high flow rates, buoyancy influence could be neglected and there are clearly other mechanisms causing the decrease in heat transfer at high coolant flow rates.

Numerical Study of Aerodynamic Losses of Effusion Cooling Holes in Aero-Engine Combustor Liners

2010 ◽  
Author(s):  
A. Andreini ◽  
A. Bonini ◽  
G. Caciolli ◽  
B. Facchini ◽  
S. Taddei
Keyword(s):  
Mass Flow ◽  
Cooling System ◽  
Numerical Study ◽  
Data Set ◽  
Flow Rates ◽  
Discharge Coefficients ◽  
Wide Range ◽  
Depth Analysis ◽  
Aero Engine ◽  
Mass Flow Rates

Due to the stringent cooling requirements of novel aeroengines combustor liners, a comprehensive understanding of the phenomena concerning the interaction of hot gases with typical coolant jets plays a major role in the design of efficient cooling systems. In this work an aerodynamic analysis of the effusion cooling system of an aero-engine combustor liner was performed; the aim was the definition of a correlation for the discharge coefficient (CD) of the single effusion hole. The data was taken from a set of CFD RANS simulations, in which the behavior of the effusion cooling system was investigated over a wide range of thermo fluid-dynamics conditions. In some of these tests, the influence on the effusion flow of an additional air bleeding port was taken in account, making possible to analyze its effects on effusion holes CD. An in depth analysis of the numerical data set has pointed out the opportunity of an efficient reduction through the ratio of the annulus and the hole Reynolds numbers: the dependence of the discharge coefficients from this parameter is roughly linear. The correlation was included in an in-house one dimensional thermo-fluid network solver and its results were compared with CFD data. An overall good agreement of pressure and mass flow rates distributions was observed. The main source of inaccuracy was observed in the case of relevant air bleed mass flow rates, due to the inherent three-dimensional behavior of the flow close to bleed opening. An additional comparison with experimental data was performed in order to improve the confidence in the accuracy of the correlation: within the validity range of pressure ratio in which the correlation is defined (> 1.02), this comparison pointed out a good reliability in the prediction of discharge coefficients. An approach to model air bleeding was then proposed, with the assessment of its impact on liner wall temperature prediction.

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