Experimental Correlation of a Thermal / Fluid Dynamic / Electrical Performance Model of a Multiple-Tube, Vapor-Anode AMTEC Cell

1999 ◽  
Author(s):  
Terry J. Hendricks ◽  
Chendong Huang ◽  
Joseph C. Giglio
Keyword(s):  
Test Data ◽  
Model Prediction ◽  
Cell Model ◽  
Performance Model ◽  
Cell Performance ◽  
High Current ◽  
Current Voltage ◽  
Wide Range ◽  
Model Predictions ◽  
Prediction Test

Abstract An AMTEC (Alkali-Metal Thermal-to-Electric Conversion) cell performance analysis model described by Hendricks et al. (1998) has been correlated with experimental data by comparing its predictions for Beta” alumina solid electrolyte (BASE) and evaporator temperatures, voltage, power output, and conversion efficiency with experimental measurements on two versions of a PX-6 AMTEC cell. The critical features of this AMTEC cell model, the PX-6 experimental set up and testing, and the model correlation PX-6 test data are discussed in this work. Model prediction/test data comparisons are presented across a wide range of current-voltage conditions and hot side temperatures for two significantly different cell lengths. Cell model predictions demonstrate good agreement with experimental PX-6 test data in simultaneously predicting BASE tube and evaporator temperatures, the onset of sodium (Na) condensation in the BASE tubes, current-voltage characteristics, and power output in high current ranges (i.e., > 1.5 A). The model also has demonstrated good capability to predict cell conversion efficiency at high currents when Na is not condensing in the BASE tubes. The good model prediction/test data comparisons have demonstrated the progress in developing this cell performance model and increased confidence in its technical foundations, algorithm implementation, and capability to predict AMTEC cell performance. The AMTEC cell model’s capability to simultaneously predict many critical cell performance parameters across a wide range of hot side temperatures, at high current conditions, and different cell lengths demonstrates the progress that has been made in its development. It has demonstrated good predictive capability, utility, and flexibility as a performance design and analysis tool for sophisticated AMTEC cell design. Testing limitations prevented testing at low current levels (i.e., < 1.5 A), so future experimental validation studies should focus on correlating model predictions at low currents.

scholarly journals Deconvolution of Gas Diffusion Polarization in Ni/Gadolinium-Doped Ceria Fuel Electrodes

2021 ◽  
Author(s):  
Cedric Grosselindemann ◽  
Niklas Russner ◽  
Sebastian Dierickx ◽  
Florian Wankmueller ◽  
Andre Weber
Keyword(s):  
Cell Model ◽  
Gas Diffusion ◽  
Transport Parameter ◽  
Inert Component ◽  
Fuel Gas ◽  
Current Voltage ◽  
Wide Range ◽  
Diffusion Polarization ◽  
Precise Quantification ◽  
Hydrogen Electrooxidation

Abstract The deconvolution of physicochemical processes in impedance spectra of SOCs with nickel/ceria fuel electrodes is challenging as gas diffusion strongly overlaps with the electrochemical processes at fuel and air electrode. To overcome this issue, symmetrical cells were applied and the gas diffusion process at the fuel electrode was quantified by altering the inert component (nitrogen / helium) in a ternary fuel gas mixture. An effective gas transport parameter considering microstructural and geometrical features was derived, enabling a precise quantification of polarization resistances related to gas diffusion and hydrogen electrooxidation. The obtained values were applied to parameterize a dc cell model. The model validation in fuel cell and electrolyzer mode showed an excellent agreement between measured and simulated current/voltage characteristics over a wide range of technically meaningful gas compositions and operating temperatures.

Rotordynamic Performance of an Oil-Free Turbocharger Supported on Gas Foil Bearings: Effects of an Assembly Radial Clearance

2010 ◽  
Author(s):  
Tae Ho Kim ◽  
Jangwon Lee ◽  
Chang Ho Kim ◽  
Yong-Bok Lee
Keyword(s):  
Test Data ◽  
Static Load ◽  
Pressure Sensors ◽  
Engine Oil ◽  
Radial Clearance ◽  
Performance Measurements ◽  
Film Pressure ◽  
Foil Bearings ◽  
Wide Range ◽  
Model Predictions

Oil-free turbochargers (TCs) will increase power and efficiency of internal combustion (IC) engines, sparking ignition (SI) and compression ignition (CI), without engine oil lubricant feeding and scheduled maintenance. Implementing gas foil bearings (GFBs) into passenger vehicle TCs enables compact, light weight, oil-free systems along with accurate shaft motions, while engine oil lubricated TCs with floating ring bearings (FRBs) are prone to show severe sub synchronous motions over a wide range of shaft speeds due to instability. The paper presents static load-deflection tests of TC GFB structure, and rotordynamic performance measurements of an oil-free TC unit supported on test GFBs. Three metal shims inserted under the bump-strip layers and in contact with the bearing housing create a mechanical preload, which induces a hydrodynamic wedge in the assembly radial clearance to generate more film pressure for the shimmed GFB. Static load-deflection tests estimate the assembly radial clearances of the shimmed GFB smaller than that of the original GFB. Model predictions agree well with test data. The discrepancy between the model predictions and test data is attributed to fabrication inaccuracy of the top foil and bump strip layers. The rotordynamic TC test rig is driven by pressurized air. The test TC rotor, of 335 gram weight and 117 mm length, is coated using commercially available wear-resistant solid lubricant, Amorphous M, to prevent severe wears during start up and shutdown in the absence of an air film. Pressure sensors measure the driving turbine inlet air pressure and a control valve changes the air mass flow manually. A pairs of optical proximity probes positioned orthogonally at the compressor end record the lateral rotor motions. Rotordynamic test results show that the shimmed GFB attenuates significantly the large amplitude of subsynchronous whirl motions arising for the original GFBs. Mechanical preloads, which determine the assembly radial clearance of the shimmed GFB, causes the increase in the rotor-bearing system natural frequency.

scholarly journals Study and Assessment of Defect and Trap Effects on the Current Capabilities of a 4H-SiC-Based Power MOSFET

Electronics ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 735
Author(s):  
Fortunato Pezzimenti ◽  
Hichem Bencherif ◽  
Giuseppe De Martino ◽  
Lakhdar Dehimi ◽  
Riccardo Carotenuto ◽  
...  
Keyword(s):  
Drain Current ◽  
Oxide Semiconductor ◽  
Temperature Dependent ◽  
Channel Mobility ◽  
Blocking Voltage ◽  
Current Voltage ◽  
Wide Range ◽  
Temperature Ranges ◽  
Joint Contribution ◽  
State Resistance

A numerical simulation study accounting for trap and defect effects on the current-voltage characteristics of a 4H-SiC-based power metal-oxide-semiconductor field effect transistor (MOSFET) is performed in a wide range of temperatures and bias conditions. In particular, the most penalizing native defects in the starting substrate (i.e., EH6/7 and Z1/2) as well as the fixed oxide trap concentration and the density of states (DoS) at the 4H-SiC/SiO2 interface are carefully taken into account. The temperature-dependent physics of the interface traps are considered in detail. Scattering phenomena related to the joint contribution of defects and traps shift the MOSFET threshold voltage, reduce the channel mobility, and penalize the device current capabilities. However, while the MOSFET on-state resistance (RON) tends to increase with scattering centers, the sensitivity of the drain current to the temperature decreases especially when the device is operating at a high gate voltage (VGS). Assuming the temperature ranges from 300 K to 573 K, RON is about 2.5 MΩ·µm2 for VGS > 16 V with a percentage variation ΔRON lower than 20%. The device is rated to perform a blocking voltage of 650 V.

Near-Wall Microlayer Evaporation Analysis and Experimental Study of Nucleate Pool Boiling on Inclined Surfaces

1998 ◽  
Vol 120 (3) ◽  
pp. 641-653 ◽  
Author(s):  
G. F. Naterer ◽  
W. Hendradjit ◽  
K. J. Ahn ◽  
J. E. S. Venart
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heating Surface ◽  
Nucleate Boiling ◽  
Inclined Surfaces ◽  
Wide Range ◽  
Model Predictions ◽  
Microlayer Evaporation ◽  
Near Wall

Boiling heat transfer from inclined surfaces is examined and an analytical model of bubble growth and nucleate boiling is presented. The model predicts the average heat flux during nucleate boiling by considering alternating near-wall liquid and vapor periods. It expresses the heat flux in terms of the bubble departure diameter, frequency and duration of contact with the heating surface. Experiments were conducted over a wide range of upward and downward-facing surface orientations and the results were compared to model predictions. More active microlayer agitation and mixing along the surface as well as more frequent bubble sweeps along the heating surface provide the key reasons for more effective heat transfer with downward facing surfaces as compared to upward facing cases. Additional aspects of the role of surface inclination on boiling dynamics are quantified and discussed.

Analysis of Thick-Walled Pipeline Elements Operating in Creep Conditions

2015 ◽  
Vol 712 ◽  
pp. 63-68
Author(s):  
Przemysław Osocha ◽  
Bohdan Węglowski
Keyword(s):  
Finite Element ◽  
Test Data ◽  
Creep Test ◽  
Power Plants ◽  
Steam Pressure ◽  
Creep Model ◽  
Creep Process ◽  
Fe Model ◽  
Element Analysis ◽  
Wide Range

In some coal-fired power plants, pipeline elements have worked for over 200 000 hours and increased number of failures is observed. The paper discuses thermal wear processes that take place in those elements and lead to rupture. Mathematical model based on creep test data, and describing creep processes for analyzed material, has been developed. Model has been verified for pipeline operating temperature, lower than tests temperature, basing on Larson-Miller relation. Prepared model has been used for thermal-strength calculations based on a finite element method. Processes taking place inside of element and leading to its failure has been described. Than, basing on prepared mathematical creep model and FE model introduced to Ansys program further researches are made. Analysis of dimensions and shape of pipe junction and its influence on operational element lifetime is presented. In the end multi variable dependence of temperature, steam pressure and element geometry is shown, allowing optimization of process parameters in function of required operational time or maximization of steam parameters. The article presents wide range of methods. The creep test data were recalculated for operational temperature using Larson-Miller parameter. The creep strain were modelled, used equations and their parameters are presented. Analysis of errors were conducted. Geometry of failing pipe junction was introduced to the Ansys program and the finite element analysis of creep process were conducted.

Uncertainty in Collapse Strength Prediction of Sandwich Pipelines

2021 ◽  
Author(s):  
U. Bhardwaj ◽  
A. P. Teixeira ◽  
C. Guedes Soares
Keyword(s):  
Probabilistic Models ◽  
Uncertainty Propagation ◽  
Simulation Method ◽  
External Pressure ◽  
Design Parameters ◽  
Collapse Strength ◽  
Parameters Uncertainty ◽  
Wide Range ◽  
Model Predictions ◽  
Strength Models

Abstract This paper assesses the uncertainty in the collapse strength of sandwich pipelines under external pressure predicted by various strength models in three categories based on interlayer adhesion conditions. First, the validity of the strength models is verified by comparing their predictions with sandwich pipeline collapse test data and the corresponding model uncertainty factors are derived. Then, a parametric analysis of deterministic collapse strength predictions by models is conducted, illustrating insights of models’ behaviour for a wide range of design configurations. Furthermore, the uncertainty among different model predictions is perceived at different configurations of outer and inner pipes and core thicknesses. A case study of a realistic sandwich pipeline is developed, and probabilistic models are defined to basic design parameters. Uncertainty propagation of models’ predictions is assessed by the Monte Carlo simulation method. Finally, the strength model predictions of sandwich pipelines are compared to that of an equivalent single walled pipe.

scholarly journals Characterizing global expansion evolution of the ionized matter in planetary nebulae

2016 ◽  
Vol 12 (S323) ◽  
pp. 352-353
Author(s):  
J. A. López ◽  
M. G. Richer ◽  
M. Pereyra ◽  
M. T. García-Díaz
Keyword(s):  
Galactic Halo ◽  
Evolutionary Rate ◽  
Planetary Nebulae ◽  
Central Star ◽  
Global Expansion ◽  
Kinematic Evolution ◽  
Wide Range ◽  
Model Predictions ◽  
First Time ◽  
Highly Evolved

AbstractBulk outflow or global expansion velocities are presented for a large number of planetary nebulae (PNe) that span a wide range of evolutionary stages and different stellar populations. The sample comprises 133 PNe from the Galactic bulge, 100 mature and highly evolved PNe from the disk, 11 PNe from the Galactic halo and 15 PNe with very low central star masses and low metallicities, for a total of 259 PNe. These results reveal from a statistical perspective the kinematic evolution of the expansion velocities of PNe in relation to changing characteristics of the central star’s wind and ionizing luminosity and as a function of the evolutionary rate determined by the central (CS) mass. The large number of PNe utilized in this work for each group of PNe under study and the homogeneity of the data provide for the first time a solid benchmark form observations for model predictions, as has been described by López et al. (2016).

scholarly journals "Creep currents" in single frog atrial cells may be generated by electrogenic Na/Ca exchange.

1986 ◽  
Vol 87 (6) ◽  
pp. 857-884 ◽  
Author(s):  
J R Hume ◽  
A Uehara
Keyword(s):  
Voltage Clamp ◽  
Time Course ◽  
Single Cells ◽  
Mechanical Activity ◽  
Common Mechanism ◽  
Mechanical Relaxation ◽  
Equilibrium Conditions ◽  
Atrial Cells ◽  
Current Voltage ◽  
Wide Range

The objective of these experiments was to test the hypothesis that the "creep currents" induced by Na loading of single frog atrial cells (Hume, J. R., and A. Uehara. 1986. Journal of General Physiology. 87:833) may be generated by an electrogenic Na/Ca exchanger. Creep currents induced by Na loading were examined over a wide range of membrane potentials. During depolarizing voltage-clamp pulses, outward creep currents were observed, followed by inward creep currents upon the return to the holding potential. During hyperpolarizing voltage-clamp pulses, creep currents of the opposite polarity were observed: inward creep currents were observed during the pulses, followed by outward creep currents upon the return to the holding potential. The current-voltage relations for inward and outward creep currents in response to depolarizing or hyperpolarizing voltage displacements away from the holding potential all intersect the voltage axis at a common potential, which indicates that inward and outward creep currents may have a common reversal potential under equilibrium conditions and may therefore be generated by a common mechanism. Measurements of inward creep currents confirm that voltage displacements away from the holding potential rapidly alter equilibrium conditions. Current-voltage relationships of inward creep currents after depolarizing voltage-clamp pulses are extremely labile and depend critically upon the amplitude and duration of outward creep currents elicited during preceding voltage-clamp pulses. An optical monitor of mechanical activity in single cells revealed (a) a similar voltage dependence for the outward creep currents induced by Na loading and tonic contraction, and (b) a close correlation between the time course of the decay of the inward creep current and the time course of mechanical relaxation. A mathematical model of electrogenic Na/Ca exchange (Mullins, L.J. 1979. Federation Proceedings. 35:2583; Noble, D. 1986. Cardiac Muscle. 171-200) can adequately account for many of the properties of creep currents. It is concluded that creep currents in single frog atrial cells may be attributed to the operation of an electrogenic Na/Ca exchange mechanism.

A Methodology for Assessing Fuel Cell Performance Under a Wide Range of Operational Conditions: Results for Single Cells

2006 ◽  
Vol 3 (3) ◽  
pp. 226-233 ◽  
Author(s):  
Andrea Baratella ◽  
Roberto Bove ◽  
Piero Lunghi
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Single Cells ◽  
Cell Performance ◽  
Effective Parameters ◽  
Test Procedures ◽  
Operational Conditions ◽  
Fuel Cell Performance ◽  
Wide Range ◽  
The University

Testing the performance of fuel cells is an important key for verifying technology improvements and for demonstrating their potential. However, due to the novelty of this technology, there is not a standardized procedure for testing fuel cell performance. In order to fully investigate fuel cell performance, the behavior must be known under a wide range of operational conditions. Furthermore, in order to compare results coming from different test teams, a set of procedures and parameters to evaluate single cell performance should be defined. The research group of the Fuel Cell Laboratory of the University of Perugia is conducting performance tests on single cells, focusing on defining test procedures to find effective parameters to be used to compare tests performed by different teams. This work demonstrates how the testing parameters developed by the team allow one to perform advanced control on test procedures, to understand test results, and to compare them with tests carried out under different operational conditions. The entire analysis is easily conducted by using a single parameter variation hyperspace approach. The experimental results obtained on single fuel cells are reported.

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