The Influence of Radiation on Arc Constriction in the Anode Region

1975 ◽  
Vol 97 (1) ◽  
pp. 41-46 ◽  
Author(s):  
E. Pfender ◽  
J. Schafer
Keyword(s):  
Analytical Model ◽  
Atmospheric Pressure ◽  
High Intensity ◽  
Radiation Effects ◽  
Relaxation Method ◽  
Anode Region ◽  
Conservation Equations ◽  
Radiation Losses ◽  
Argon Arcs

An improved analytical model for the description of the anode contraction zone of a high intensity arc takes radiation effects into account. The conservation equations for the anode contraction zone and the adjacent undisturbed arc column are solved numerically with a relaxation method. Results for atmospheric pressure argon arcs at three different currents demonstrate that radiation losses reduce temperature peaks substantially and, at the same time, provide a smooth matching of arc column and contraction zone solutions. Although the model seems to be adequate for a large portion of the anode contraction zone, the results indicate that refinements of the model are necessary for the region close to the anode, in particular, deviations from LTE have to be taken into account.

scholarly journals Влияние предыонизации на микроканальную структуру искрового разряда в воздухе в промежутке острие-плоскость

2022 ◽  
Vol 92 (1) ◽  
pp. 52
Author(s):  
А.А. Тренькин ◽  
К.И. Алмазова ◽  
А.Н. Белоногов ◽  
В.В. Боровков ◽  
Е.В. Горелов ◽  
...  
Keyword(s):  
Wave Front ◽  
Electron Concentration ◽  
Atmospheric Pressure ◽  
Initial Phase ◽  
Discharge Channel ◽  
Cathode Region ◽  
Ionization Wave ◽  
Anode Region ◽  
Microstructure Formation ◽  
Micron Diameter

The initial phase of a spark discharge in the gap between the pin (cathode) and a plane 1.5 mm long in atmospheric pressure air under conditions of preliminary photoionization by an auxiliary discharge was investigated by the method of shadow photography. In the absence of preionization, the discharge from the first nanoseconds after breakdown is an aggregate of a large number of micron-diameter channels. It was found that the electron concentration resulting from preionization, estimated at 108  109 cm-3, increases the degree of uniformity of the discharge channel in the near-cathode region; however, in the near-anode region, the channel remains microstructured. Within the framework of the mechanism of microstructure formation due to the instability of the ionization wave front, a criterion for the formation of a uniform discharge is obtained and an explanation of the results obtained is presented.

Application of the 3ω Hot Wire Technique for Measurement of Fluid Thermophysical Properties

2007 ◽  
Author(s):  
Brandon W. Olson ◽  
Ali Fahham
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Analytical Model ◽  
Thermophysical Properties ◽  
Fluid Motion ◽  
Hot Wire ◽  
Resistance Thermometer ◽  
Bulk Fluid ◽  
Radiation Losses ◽  
Fluid Properties

The popular 3ω method of measuring thermophysical properties of solids is adapted for the simultaneous measurement of thermal conductivity and heat capacity in both liquids and gases. This technique is experimentally simple and has a lower susceptibility to random experimental noise, bulk fluid motion, radiation losses, and non-linear effects than other transient hot wire measurement methods. The compactness of the 3ω hotwire allows it to be used with different fluids in a variety of circumstances with very little specialized experimental equipment. Both the experimental setup and theoretical model are detailed. Experimental 3ω measurements were made in a variety of common fluids (air, water, and mineral oil) using commercially drawn 10μm platinum and 5μm tungsten hot wires which serve as both heating element and resistance thermometer. Measurements taken over a range of frequencies are numerically reduced to provide both thermal conductivity and heat capacity information. Experimental measurements and the corresponding analytical model are presented in terms of impedance or thermal resistance; a more physically meaningful and intuitive basis of comparison. Fluid properties are determined by curve-fitting an analytical model to experimental data using a least-squares approach. This technique allows both thermal conductivity and heat capacity (or thermal diffusivity) to be uniquely determined from a single measurement sequence.

Studies of the anode region of a high‐intensity argon arc

1982 ◽  
Vol 53 (6) ◽  
pp. 4136-4145 ◽  
Author(s):  
N. Sanders ◽  
K. Etemadi ◽  
K. C. Hsu ◽  
E. Pfender
Keyword(s):  
High Intensity ◽  
Anode Region

scholarly journals The age-stratified analytical model for the spread of the COVID-19 epidemic

2021 ◽  
Author(s):  
Felix Mairanowski ◽  
Denis Below
Keyword(s):  
Analytical Model ◽  
High Intensity ◽  
Age Groups ◽  
Observation Data ◽  
Age Group ◽  
Epidemic Spread ◽  
Intensity Of Infection ◽  
Good Correspondence ◽  
Contact Patterns ◽  
Comparison Of The Results

The previously developed ASILV model for calculating epidemic spread under conditions of lockdown and mass vaccination was modified to analyse the intensity of COVID-19 infection growth in the allocated age groups. Comparison of the results of calculations of the epidemic spread, as well as the values of the seven-day incidence values with the corresponding observation data, shows their good correspondence for each of the selected age groups. The greatest influence on the overall spread of the epidemic is in the 20-40 age groups. The relatively low level of vaccination and the high intensity of contact in these age groups contributes to the emergence of new waves of the epidemic, which is especially active when the virus mutates and the lockdown conditions are relaxed. The intensity of the epidemic in the 90+ age group has some peculiarities compared to other groups, which may be explained by differences in contact patterns among individuals in this age group compared to others. Approximate ratios for estimating mortality as a function of the intensity of infection for individual age groups are provided. The proposed stratified ASILV model by age group will allow more detailed and accurate prediction of the spread of the COVID-19 epidemic, including when new, more transmissible versions of the virus mutate and emerge.

Sign in / Sign up

Export Citation Format

Share Document