scholarly journals Atmospheric Argon Free burning Arcs with a Simplified Unified Model Using CFD-Arc Modeling

10.14311/1757 ◽  
2013 ◽  
Vol 53 (2) ◽  
Author(s):  
Won-Ho Lee ◽  
Jong-Chul Lee
Keyword(s):  
Steady State ◽  
Atmospheric Pressure ◽  
Measured Data ◽  
Unified Model ◽  
Anode Surface ◽  
Work Piece ◽  
Arc Voltage ◽  
Atmospheric Argon

Free burning arcs, where the work piece acts as an anode, are frequently used for a number of applications. Our investigation is exclusively concerned with a simplified unified model of arcs and their electrodes under steady state conditions at atmospheric pressure. The model is used to make predictions of arc and electrode temperatures and arc voltage for a 200 A arc in argon. The computed temperatures along the axis between the cathode tip and the anode surface compare well the measured data.

scholarly journals Three-Dimensional Computations of Free-Burning Arcs and Their Surroundings

2016 ◽  
Vol 3 (3) ◽  
pp. 151-154
Author(s):  
W. Lee ◽  
J. Lee
Keyword(s):  
High Intensity ◽  
Three Dimensional ◽  
Measured Data ◽  
Numerical Results ◽  
Anode Surface ◽  
Arc Voltage ◽  
Model Free ◽  
Good Agreement ◽  
Argon Arcs

This paper is concerned with developing a capability to model free-burning high-intensity argon arcs and enhancing the accuracy of numerical results according to three-dimensional calculations. It was found that the computed temperatures along the axis between the cathode tip and the anode surface show good agreement with two different measured data. Although the LTE model can reasonably predict the overall arc voltage for free-burning arcs, it fails to account accurately what happens at the regions near electrodes.

Pitfalls for Accurate Steady-State Port Flow Simulations

2012 ◽  
Author(s):  
Xiaofeng Yang ◽  
Zhaohui Chen ◽  
Tang-Wei Kuo
Keyword(s):  
Steady State ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Measured Data ◽  
Steady State Flow ◽  
Bench Tests ◽  
Flow Simulations ◽  
Mesh Topology ◽  
State Flow

Steady-state port flow simulations were carried out with a commercial three dimensional (3D) Computational Fluid Dynamics (CFD) code using Cartesian mesh with cut cells to study the prediction accuracy. The accuracy is assessed by comparing predicted and measured mass-flow rate and swirl and tumble torques at various valve lifts using different boundary condition setup and mesh topology relative to port orientation. The measured data is taken from standard steady-state flow bench tests of a production intake port. The predicted mass-flow rates agree to within 1% with the measured data between the intermediate and high valve lifts. At low valve lifts, slight over prediction in mass-flow rate can be observed. The predicted swirl and tumble torques are within 25% of the flow bench measurements. Several meshing parameters were examined in this study. These include: inlet plenum shape and outlet plenum/extension size, embedded sphere with varying minimum mesh size, finer meshes on port and valve surface, orientation of valve and port centerline relative to the mesh lines. For all model orientations examined, only the mesh topology with the valve axis aligned closely with the mesh lines can capture the mass-flow rate drop for very high valve lifts due to flow separation. This study further demonstrated that it is possible to perform 3D CFD flow analyses to adequately simulate steady-state flow bench tests.

scholarly journals Reconstructing bottom water temperatures from measurements of temperature and thermal diffusivity in marine sediments

2014 ◽  
Vol 11 (5) ◽  
pp. 2391-2422
Author(s):  
F. Miesner ◽  
A. Lechleiter ◽  
C. Müller
Keyword(s):  
Steady State ◽  
Heat Flow ◽  
Water Temperature ◽  
Marine Sediments ◽  
Bottom Water ◽  
Measured Data ◽  
Temperature History ◽  
Artificial Data ◽  
Bottom Water Temperature ◽  
Steady State Heat

Abstract. Temperature fields in marine sediments are studied for various purposes. Often, the target of research is the steady state heat flow as a (possible) source of energy but there are also studies attempting to reconstruct bottom water temperature variations to understand more about climate history. The bottom water temperature propagates into the sediment to different depths, depending on the amplitude and period of the deviation. The steady state heat flow can only be determined when the bottom water temperature is constant while the bottom water temperature history can only be reconstructed when the deviation has an amplitude large enough or the measurements are taken in great depths. In this work, the aim is to reconstruct recent bottom water temperature history such as the last two years. To this end, measurements to depths of up to 6 m shall be adequate and amplitudes smaller than 1 K should be reconstructable. First, a commonly used forward model is introduced and analyzed: knowing the bottom water temperature deviation in the last years and the thermal properties of the sediments, the forward model gives the sediment temperature field. Next, an inversion operator and two common inversion schemes are introduced. The analysis of the inversion operator and both algorithms is kept short, but sources for further reading are given. The algorithms are then tested for artificial data with different noise levels and for two example data sets, one from the German North Sea and one from the Davis Strait. Both algorithms show good and stable results for artificial data. The achieved results for measured data have low variances and match to the observed oceanographic settings. Lastly, the desired and obtained accuracy are discussed. For artificial data, the presented method yields satisfying results. However, for measured data the interpretation of the results is more difficult as the exact form of the bottom water deviation is not known. Nevertheless, the presented inversion method seems rather promising due to its accuracy and stability for artificial data. Continuing to work on the development of more sophisticated models for the bottom water temperature, we hope to cover more different oceanographic settings in the future.

Characterization of a Radiantly Driven Multistage Knudsen Compressor

2003 ◽  
Author(s):  
M. Young ◽  
Y. L. Han ◽  
E. P. Muntz ◽  
G. Shiflett
Keyword(s):  
Steady State ◽  
Atmospheric Pressure ◽  
Maximum Flow ◽  
Performance Model ◽  
Experimental Results ◽  
Maximum Pressure ◽  
Flow Rates ◽  
Micro Scale ◽  
Knudsen Compressors

Knudsen Compressors are meso/micro scale gas compressors/pumps based on thermal transpiration or thermal creep. The design of radiantly driven Knudsen Compressors is discussed, along with a model that was developed to understand their performance. Experimental pumping performances for Knudsen Compressors with one, two, five, and fifteen stage, radiantly driven cascades are also discussed. Temperature measurements across the transpiration membranes, for various pressures of Nitrogen, were obtained and compared to those predicted by the performance model. The results agree with the model to within 15% consistently under predicting the measured hot side temperature of the transpiration membrane. The pump-down curves, steady-state maximum pressure differences, and maximum flow rates produced by a single stage Knudsen Compressor were obtained. A variety of configurations were studied at pressures from 500 mTorr to atmospheric pressure. The experimental results agreed with the performance model’s predictions to within 20%.

LIF Observation of Ground-State OH Radicals in DC Nozzle-to-Plane Positive Streamer Corona

2006 ◽  
Vol 9 (2) ◽  
Author(s):  
M. Kocik ◽  
J. Mizeraczyk ◽  
S. Kanazawa ◽  
T. Ohkubo
Keyword(s):  
Steady State ◽  
Corona Discharge ◽  
Ground State ◽  
Atmospheric Pressure ◽  
Electrode System ◽  
Oh Radicals ◽  
Two Dimensional ◽  
Electrode Gap ◽  
Streamer Corona ◽  
Positive Streamer

AbstractIn this study, the planar LIF detection of the hydroxyl (OH) radicals was performed in a nozzle-to-plane electrode system having an electrode gap of 30 mm during the steady-state positive streamer corona discharge at atmospheric pressure. For monitoring the ground-state OH radicals, OH transition at 282 nm was used. The two-dimensional OH distribution in the DC corona discharge in air/H

An on Line Method of the Steady-State Data Acquisition

2013 ◽  
Vol 385-386 ◽  
pp. 668-674
Author(s):  
Jia Yang ◽  
Hai Bao ◽  
Ling Wang ◽  
Gang Liu
Keyword(s):  
Steady State ◽  
Power System ◽  
Real Time ◽  
Power Flow ◽  
Measured Data ◽  
Electric Power System ◽  
Power Flow Calculation ◽  
Flow Calculation ◽  
State Data ◽  
The Real

Steady-state power flow calculation belongs to power system steady-state analysis, and the data used in calculation should be steady-state data. However, the existing SCADA system hasnt distinguished the transient data from the steady-state data. The real-time measured data reflect the dynamic electric power system. It is the right reason for not all of the real-time measured power can be used for power flow calculation. In another word, it causes the matching problem between measured data and power flow calculations. Based on the current situation of information collection system, the characteristics of the measured data had been analyzed in this paper. And an effective acquisition method for steady-state measured data is proposed on the theoretical basis of the law of large numbers. It uses the average value of the measured data that in the same load state to approximate the steady-state true value in one period. And the steady-state data can be used in power flow calculation. The simulation results show that the method proposed in this paper ensures the accuracy and reliability of power flow calculation.

Dynamic Measurements on a Pulsed Short Arc Driven by a Magnetic Field

1973 ◽  
Vol 51 (14) ◽  
pp. 1499-1504 ◽  
Author(s):  
Michel G. Drouet ◽  
Rosario Beaudet
Keyword(s):  
Magnetic Field ◽  
Atmospheric Pressure ◽  
Streak Camera ◽  
Transverse Magnetic ◽  
Temporary Increase ◽  
Dynamic Measurements ◽  
Current Step ◽  
Arc Voltage ◽  
Arc Current ◽  
Short Arc

Current and voltage measurements were performed on a short (3 mm) arc burning at atmospheric pressure in air and driven (100–200 ms−1) along two rail electrodes by a transverse magnetic field. The arc current was pulsed from a steady state value of 40 A to 200–1000 A in < 10 μs. Simultaneous measurements revealed the arc voltage to be constant. On the contrary, a stationary arc, subjected to the same current step, showed a simultaneous temporary increase of the arc voltage of 10–40 V. To facilitate the interpretation of the results, the motion of the arc was recorded using a fast streak camera. It was found that, after applying the current step, the velocity of the arc does not change instantaneously, but that the luminous plasma expands in the wake of the arc. An interpretation of the results is proposed; it is based on the assumption that in a moving arc, the distributions of the current and the conductance are not similar.

Performance Evaluation of the 200-kWth HiTRec-II Open Volumetric Air Receiver

2003 ◽  
Vol 125 (1) ◽  
pp. 87-94 ◽  
Author(s):  
Bernhard Hoffschmidt ◽  
Fe´lix M. Te´llez ◽  
Antonio Valverde ◽  
Jesu´s Ferna´ndez ◽  
Valerio Ferna´ndez
Keyword(s):  
Stainless Steel ◽  
Steady State ◽  
High Temperature ◽  
Atmospheric Pressure ◽  
Flow Instability ◽  
Steel Structure ◽  
Test Bed ◽  
Psa Test ◽  
Structural Problems ◽  
Air Temperatures

The High Temperature Receiver (HitTRec) consists of a modular ceramic absorber, a supporting structure and an air-return system. It has been designed to prevent possible flow instability at 700-800°C average outlet air temperature with atmospheric pressure. The HiTRec-II prototype was developed to solve the structural problems of the first prototype (HiTRec-I). Testing in the Plataforma Solar de Almerı´a (PSA) test bed lasted from November 2000 through May 2001, accumulating 150 test hours under concentrated sun. Results demonstrated the durability of the modified stainless-steel structure. Inlet aperture flux was up to 900kW/m2 and average outlet air temperatures of up to 840°C with peak outlet air temperatures of up to 950°C. Thermal efficiency under steady-state conditions was 76±7% at 700°C, nominal conditions for a PHOEBUS-type volumetric receiver. Other performance characteristics were also evaluated (e.g., Air Return Ratio of 46% and characteristic receiver response time of 70 s).

scholarly journals Thermal Conductivity of Steam at Atmospheric Pressure

1969 ◽  
Vol 11 (4) ◽  
pp. 392-401 ◽  
Author(s):  
T. J. S. Brain
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Steady State ◽  
Atmospheric Pressure ◽  
Concentric Cylinder ◽  
Temperature Range ◽  
Steady State Method ◽  
New Correlation ◽  
Paper Work ◽  
State Method

In this paper work carried out by the author to measure the thermal conductivity of steam at atmospheric pressure in the temperature range 100-700°C is reported. This work was undertaken in view of the discrepancies which exist in the experimental data at atmospheric pressure. In particular, the serious differences which exist at the high temperatures between the results of Russian experimenters, who give higher values than those given by American and German workers, needed investigation. Utilizing two concentric cylinder cells an absolute steady state method has been used to measure the thermal conductivity of steam in the temperature range 100-700°C, at atmospheric pressure, with a probable accuracy estimated to be within ± l·5-±2 per cent. The results obtained confirm Russian observations at the higher temperatures and it is hoped that these results will help finally to resolve the inconsistencies in the experimental data. A fresh assessment of all the experimental data is given by the author where arguments in favour of both the lower and higher atmospheric lines are discussed. A new correlation of experimental data has been undertaken and a reduction in the tolerances put on the equation defining the atmospheric line from ±3 per cent in the range 100-400°C and ±4 per cent in the range 400-700°C to ±2 per cent over the complete range 100-700°C is now recommended.

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