Development and Sensitivity Analysis of Model for Aeration Chamber in Water-Circulating Aerator

2012 ◽  
Vol 260-261 ◽  
pp. 663-668
Author(s):  
Xin Sun ◽  
Fei Fei Duan ◽  
Ting Lin Huang ◽  
Meng Dan Zhang
Keyword(s):  
Sensitivity Analysis ◽  
Flow Resistance ◽  
Mathematic Model ◽  
Resistance Coefficient ◽  
Water Velocity ◽  
Force Balance ◽  
Model Parameters ◽  
Prediction Errors ◽  
Two Phase ◽  
One Dimensional

Based on the force balance between the driving force and drag force acting on the gas-liquid two-phase flow in the aeration chamber, a one-dimensional mathematic model of water velocity for the aeration chamber was developed and solved with METLAB. Sensitivity analysis of the model parameters showed that the prediction results were greatly dependant on the flow resistance coefficient at the top (KT) and the coefficient due to local disturbances at the entrance and exit (KE). Using optimized parameters, under air flow rates higher than 0.055m³/s, prediction errors of gas holdup and water velocity can both be further decreased within ± 9%. Developed model of water velocity can be used to design and optimize the aeration chamber in the water-circulating aerator.

Sensitivity Analysis and Parameter Optimization of a Hydrodynamic Model for the Aeration Chamber in a Water-Lifting Aerator

2013 ◽  
Vol 663 ◽  
pp. 888-893
Author(s):  
Xin Sun ◽  
Fei Fei Duan ◽  
Ting Lin Huang
Keyword(s):  
Sensitivity Analysis ◽  
Hydrodynamic Model ◽  
Flow Resistance ◽  
Water Velocity ◽  
Force Balance ◽  
Model Parameters ◽  
Total Force ◽  
Two Phase ◽  
Optimized Model ◽  
Resistance Coefficients

A one-dimensional hydrodynamic model for the aeration chamber in the water-lifting aerator was developed on the basis of the total force balance between the driving force and flow resistance acting on the gas-liquid two-phase flow. Water velocity in the aeration chamber was predicted under different combinations of flow resistance coefficients at the top (KT) and the entrance and exit (KE), the results of sensitivity analysis showed that both KT and KE have significant effect on the predicted water velocity and gas holdup in the riser of the aeration chamber. Taking the water velocity as the main objective, flow resistance coefficients of KT and KE were optimized as and , where Ulr is the superficial water velocity. Using optimized model parameters, the water velocities were well predicted within ±7% of the measured ones respectively.

Sensitivity Analysis of One-Dimensional Heat Transfer in Tissue With Temperature-Dependent Perfusion

1997 ◽  
Vol 119 (1) ◽  
pp. 77-80 ◽  
Author(s):  
C. R. Davies ◽  
G. M. Saidel ◽  
H. Harasaki
Keyword(s):  
Heat Transfer ◽  
Sensitivity Analysis ◽  
Heated Surface ◽  
Experimental Studies ◽  
Total Artificial Heart ◽  
Tissue Temperature ◽  
Model Parameters ◽  
Temperature Dependent ◽  
One Dimensional

Design criteria for implantable, heat-generating devices such as the total artificial heart require the determination of safe thresholds for chronic heating. This involves in-vivo experiments in which tissue temperature distributions are obtained in response to known heat sources. Prior to experimental studies, simulation using a mathematical model can help optimize the design of experiments. In this paper, a theoretical analysis of heat transfer is presented that describes the dynamic, one-dimensional distribution of temperature from a heated surface. Loss of heat by perfusion is represented by temperature-independent and temperature-dependent terms that can reflect changes in local control of blood flow. Model simulations using physiologically appropriate parameter values indicate that the temperature elevation profile caused by a heated surface adjacent to tissue may extend several centimeters into the tissue. Furthermore, sensitivity analysis indicates the conditions under which temperature profiles are sensitive to changes in thermal diffusivity and perfusion parameters. This information provides the basis for estimation of model parameters in different tissues and for prediction of the thermal responses of these tissues.

Systematic Parameter Estimation and Sensitivity Analysis Using a Multidimensional PEMFC Model Coupled With DAKOTA

2010 ◽  
Author(s):  
Brian Carnes ◽  
Ken S. Chen ◽  
Fangming Jiang ◽  
Gang Luo ◽  
Chao-Yang Wang
Keyword(s):  
Sensitivity Analysis ◽  
Parameter Estimation ◽  
Proton Exchange Membrane ◽  
Computational Models ◽  
Proton Exchange ◽  
Operating Conditions ◽  
Critical Parameters ◽  
Model Parameters ◽  
Two Phase ◽  
Manual Adjustment

Current computational models for proton exchange membrane fuel cells (PEMFCs) include a large number of parameters such as boundary conditions, material properties, and numerous parameters used in sub-models for membrane transport, two-phase flow and electrochemistry. In order to successfully use a computational PEMFC model in design and optimization, it is important to identify critical parameters under a wide variety of operating conditions, such as relative humidity, current load, temperature, etc. Moreover, when experimental data is available in the form of polarization curves or local distribution of current and reactant/product species (e.g., O2, H2O concentrations), critical parameters can be estimated in order to enable the model to better fit the data. Sensitivity analysis and parameter estimation are typically performed using manual adjustment of parameters, which is also common in parameter studies. We present work to demonstrate a systematic approach based on using a widely available toolkit developed at Sandia called DAKOTA that supports many kinds of design studies, such as sensitivity analysis as well as optimization and uncertainty quantification. In the present work, we couple a multidimensional PEMFC model (which is being developed, tested and later validated in a joint effort by a team from Penn State Univ. and Sandia National Laboratories) with DAKOTA through the mapping of model parameters to system responses. Using this interface, we demonstrate the efficiency of performing simple parameter studies as well as identifying critical parameters using sensitivity analysis. Finally, we show examples of optimization and parameter estimation using the automated capability in DAKOTA.

Single- and Two-Phase Diversion Cross-Flows Between Triangle Tight Lattice Rod Bundle Subchannels: Data on Flow Resistance and Interfacial Friction Coefficients for the Cross-Flow

2006 ◽  
Author(s):  
Tatsuya Higuchi ◽  
Akimaro Kawahara ◽  
Michio Sadatomi ◽  
Hiroyuki Kudo
Keyword(s):  
Friction Coefficient ◽  
Pressure Difference ◽  
Flow Resistance ◽  
Cross Flow ◽  
Resistance Coefficient ◽  
Interfacial Friction ◽  
Two Phase ◽  
Rod Bundle ◽  
The Cross ◽  
Tight Lattice

Single- and two-phase diversion cross-flows arising from the pressure difference between tight lattice subchannels are our concern in this study. In order to obtain a correlation of the diversion cross-flow, we conducted adiabatic experiments using a vertical multiple-channel with two subchannels simplifying the triangle tight lattice rod bundle for air-water flows at room temperature and atmospheric pressure. In the experiments, data were obtained on the axial variations in the pressure difference between the subchannels, the ratio of flow rate in one subchannel to the whole channel, the void fraction in each subchannel for slug-churn and annular flows in two-phase flow case. These data were analyzed by use of a lateral momentum equation based on a two-fluid model to determine both the cross-flow resistance coefficient between liquid phase and channel wall and the gas-liquid interfacial friction coefficient. The resulting coefficients have been correlated in a way similar to that developed for square lattice subchannel case by Kano et al. (2002); the cross-flow resistance coefficient data can be well correlated with a ratio of the lateral velocity due to the cross-flow to the axial one irrespective of single- and two-phase flows; the interfacial friction coefficient data were well correlated with a Reynolds number, which is based on the relative velocity between gas and liquid cross-flows as the characteristic velocity.

scholarly journals DEM--CFD modeling and simulations of hydrodynamic characteristics and flow resistance coefficient in fixed-bed reactors

2021 ◽  
Author(s):  
Yaping Li ◽  
Le Xie ◽  
Yonghua Zhou ◽  
Chongwen Jiang ◽  
Hong Zhong
Keyword(s):  
Pressure Drop ◽  
Flow Resistance ◽  
Fixed Bed ◽  
Resistance Coefficient ◽  
Spherical Particles ◽  
Hydrodynamic Characteristics ◽  
Model Parameters ◽  
Large Set ◽  
Fixed Bed Reactors ◽  
Fixed Beds

The ability to predict void fraction, pressure drop, and flow resistance coefficient in fixed-bed reactors is significant to their optimal design. In this study, the discrete element method (DEM) is combined with computational fluid dynamics (CFD) to simulate the hydrodynamic characteristics of fixed-beds. A realistic random packing structure for fixed-beds with spherical particles was generated via the DEM method and then meshed using Ansys ICEM software for the CFD simulation. A grid independency study was performed to select appropriate grid model parameters. A large set of numerical experiments was conducted to investigate the hydrodynamic characteristics with respect to different inlet velocities and particle sizes, and the simulated pressure drop data were used to calculate the flow resistance coefficient. The output flow resistance coefficients agreed well with those calculated by the classical models in laminar and turbulent flow regimes, thereby indicating the accuracy and advantage of the proposed DEM–CFD approach.

A ONE-DIMENSIONAL TWO-PHASE FLOW MODEL AND EXPERIMENTAL VALIDATION FOR A FLASHING VISCOUS LIQUID IN A SPLASH PLATE NOZZLE

2015 ◽  
Vol 25 (9) ◽  
pp. 795-817 ◽  
Author(s):  
Mika P. Jarvinen ◽  
A. E. P. Kankkunen ◽  
R. Virtanen ◽  
P. H. Miikkulainen ◽  
V. P. Heikkila
Keyword(s):  
Viscous Liquid ◽  
Experimental Validation ◽  
Flow Model ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Two Phase ◽  
One Dimensional
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