scholarly journals Atmospheric disturbance on the gas explosion in closed fire zone

2020 ◽  
Vol 7 (4) ◽  
pp. 752-765
Author(s):  
Yulong Duan ◽  
Shuo Wang ◽  
Wenhe Wang ◽  
Kai Zheng
Keyword(s):  
Oxygen Concentration ◽  
Atmospheric Pressure ◽  
Pressure Difference ◽  
Air Leakage ◽  
Gas Emission ◽  
Time Duration ◽  
Wind Resistance ◽  
Atmospheric Disturbance ◽  
Gas Concentration ◽  
Fire Zone

AbstractIn order to avoid serious safety accidents caused by closed fire zone, based on the continuous monitoring of atmospheric pressure at different monitoring points in multiple mines, the atmospheric pressure fluctuation model and the air leakage model were established and analyzed. The change law with time of oxygen concentration and gas concentration in the fire zone were obtained due to atmospheric disturbances under the influence of different pressure difference, volume and size of fire area, wind resistance, gas emission, sealing moments, etc. so as to evaluate the explosion risk of a closed fire zone. Research showed that the mine atmosphere fluctuates with the atmosphere of ground, and the pressure difference between the inner and outer sides of the enclosed fire zone is affected by the periodic fluctuation of atmosphere, which has about 16-h cosine fluctuation and approximate 8-h fixed value. Compared with the fire zone with poor sealing quality, good sealing fire zone has better resistance to atmospheric disturbance. The reduction of oxygen concentration in the inner side of a well-sealed fire zone mainly depends on the dilution of methane, which is more likely to accumulate and rise rapidly. And the fire zone with poor sealing quality is easy to be interfered. The inner oxygen concentration and gas concentration are easily affected by the absolute gas emission and the air leakage in the fire zone. Fire zone with small wind resistance and small volume is especially obvious. At the initial stage of the closed fire zone it's very possible to happen explosion. The time duration of explosion danger varies under different conditions, and the atmospheric disturbance may lead to repeated explosions in some cases. It's suggested to take some methods to avoid explosions according to the real-time situation, closure time, oxygen concentration and gas concentration of fire zone.

Preventing Air Leakage in Negative Atmospheric Pressure Therapy for Open Fractures Treated With External Fixators

2013 ◽  
Vol 38 (12) ◽  
pp. 2520 ◽  
Author(s):  
İlhami Oğuzhan Aydoğdu ◽  
Engin Yosma ◽  
Tekin Şímşek ◽  
Musa Kemal Keleş
Keyword(s):  
Atmospheric Pressure ◽  
Open Fractures ◽  
External Fixators ◽  
Air Leakage ◽  
Pressure Therapy

Gas Concentration Distribution Law in the Roadway after Coal and Gas Outburst

2015 ◽  
Vol 713-715 ◽  
pp. 314-318
Author(s):  
Chun Li Yang ◽  
Yi Liang Zhao ◽  
Xiang Chun Li ◽  
Yang Yang Meng ◽  
Fei Fei Zhu
Keyword(s):  
Concentration Distribution ◽  
Correlation Coefficients ◽  
Coal And Gas Outburst ◽  
Gas Emission ◽  
Distribution Law ◽  
Gas Concentration ◽  
Research Results ◽  
Gas Outburst ◽  
Whole Process ◽  
Secondary Disasters

Gas emission happens after coal and gas outburst, and it could cause secondary disasters in the roadway. Therefore it is necessary to research gas concentration distribution law in the roadway after coal and gas outburst, and theoretical basis for avoiding the occurrence of secondary disasters could be provided. Based on the above, Fluent is used to simulate gas concentration distribution law in the roadway during outburst. The research results show that gas velocity of the initial stage is larger in the whole process of gas outburst and gas emission impacts opposite walls in the form of jet in the roadway intersection. The flow changes direction and moves along the main airway and return airway. It produces countercurrent along the main airway. Because the pressure in the main airway is high, gas migration velocity becomes zero after a certain distance and is "back" to return airway. The higher the outburst velocity is, the longer the flow length is. Gas concentration variation with two kinds of different outburst intensities and position are regressed and it shows that correlation coefficients of power function are the highest. The research results have a certain theoretical value to prevent the occurrence of secondary disasters after coal and gas outburst.

scholarly journals Overview of large building testing in Baltic countries

2020 ◽  
Vol 172 ◽  
pp. 05007
Author(s):  
Andrejs Nitijevskis ◽  
Vladislavs Keviss
Keyword(s):  
Quality Control ◽  
Pressure Difference ◽  
Leakage Rate ◽  
Air Leakage ◽  
Baltic Countries ◽  
Measurement Results ◽  
The Mean ◽  
Mandatory Testing ◽  
Air Leakage Rate ◽  
Large Building

The objectives of this paper are to review measurements of airtightness of 2 large building groups – middle size shops, and warehouses/distribution centres. The mean air leakage rate at 50 Pa pressure difference q50 was 1.04 m3/m2h and 1.35 m3/m2h for shops and warehouses respectively. Analysis of measurement results is valuable because it allows to make a conclusion about compliance of national and corporative construction airtightness norms with actual air barrier condition on a comissioning stage. In the concluding part of the study there are suggested ways to improve air barrier such as review of construction norms, implementation of a mandatory testing and quality control of a measurement.

scholarly journals CFD analysis of the fluid motion in the isolation rooms

2021 ◽  
Vol 850 (1) ◽  
pp. 012025
Author(s):  
P Tamil Selvan ◽  
K Abhiram ◽  
Ch Anu Raghava ◽  
V Naveen Sai
Keyword(s):  
World Health Organization ◽  
Atmospheric Pressure ◽  
Pressure Difference ◽  
Fluid Motion ◽  
Particle Diameter ◽  
World Health ◽  
Cfd Analysis ◽  
Cfd Simulations ◽  
The World ◽  
Health Organization

Abstract COVID-19 is declared as a pandemic by WHO (world health organization) which has led to many deaths all over the world. This study deals with the fluid motion in the isolation rooms with 12 or more ACH (air changes per hour) and maintaining a minimum pressure difference of 2.5 Pascal that can help in reducing the transmission of the virus from affected people. ANSI/ASHRAE guidelines are considered for the analysis. These Isolation rooms help in eradicating the spread of the contaminated particles to the surroundings by creating a pressure less than the atmospheric pressure in in the room. CFD simulations are carried to study the fluid motion of the particles emitted by the patient inside the room. The Analysis is carried out with various human cough velocities of different particle diameters and we observed from the results that the time taken by the particles to reach the exhaust increases with increase in particle diameter, and the flow inside the room increases with increase in human cough velocity.

scholarly journals Oxygen Distribution and Air Leakage Law in Gob of Working Face of U+L Ventilation System

2019 ◽  
Vol 2019 ◽  
pp. 1-10
Author(s):  
Xiaowei Zhai ◽  
Bo Wang ◽  
Shangrong Jiang ◽  
Weixia Zhang
Keyword(s):  
Oxygen Concentration ◽  
Spontaneous Combustion ◽  
Ventilation System ◽  
Burial Depth ◽  
Air Leakage ◽  
Coal Spontaneous Combustion ◽  
Working Face ◽  
Air Intake ◽  
And Control ◽  
The Relationship

In order to prevent and control coal spontaneous combustion effectively in the gob of U+L working face, the 30105 working face of Hanglaiwan mine was taken as the research object. The relationship models between oxygen concentration and burial depth of the two tunnels in the gob of U+L working face were established. The distribution of oxygen in the gob of the working face of U+L ventilation system was studied by field observation combined with numerical simulation. The results show that the air leakage in the gob is serious. There are a number of fluctuation areas where the oxygen concentration first decreases and then increases in the air intake side of the gob. The oxygen concentration peaked at 100m, 175m, and 245m, respectively, from the intake side of the gob. In the same position of the gob depth, the air leakage intensity on the intake side is generally higher than that on the return side, and the oxygen concentration on the intake side of the gob is slower than the return side. Oxygen concentration maintains at 5.09% when the depth of gob reaches 400m. Measures to prevent coal spontaneous combustion should be strengthened in the air intake side.

Determination of the Efficacy of Sterile Barrier Systems Against Microbial Challenges During Transport and Storage

2009 ◽  
Vol 30 (2) ◽  
pp. 179-183 ◽  
Author(s):  
Hartmut Dunkelberg ◽  
Ulrich Schmelz
Keyword(s):  
Atmospheric Pressure ◽  
Pressure Difference ◽  
Film Material ◽  
Plastic Film ◽  
Exposure Test ◽  
Bacterial Aerosol ◽  
Logarithmic Reduction ◽  
Pressure Changes ◽  
And Storage ◽  
Microbial Challenge

Objective.The sterility assurance level of 10−6 is an established standard that defines the quality of sterile products. The aim of the present study was to develop a method that correlated the results from microbial-barrier testing of flexible sterile barrier systems with the estimated microbial challenge that the package encounters during storage and transport.Methods.The effectiveness of microbial-barrier packaging was determined by the use of an exposure chamber test with 20 periodic atmospheric pressure changes of 50 and 70 hPa. Flexible peel pouches were used as sterile barrier systems. The logarithmic reduction value of a sterile barrier system was calculated on the basis of the experimental results and compared with the logarithmic reduction value required for the microbial challenges to maintain sterility during transport and storage.Results.For pouches made of paper and plastic-film material, a logarithmic reduction value of 5.4 was obtained on the basis of 30 of 99 plates becoming nonsterile after being exposed to a 50 hPa difference in periodic atmospheric pressure changes. For pouches made of paper and plastic-film material, a logarithmic reduction value of 5.2 was obtained on the basis of 48 of 100 plates becoming nonsterile after being exposed to a 70 hPa difference in atmospheric pressure. For pouches made of nonwoven and plastic-film material, logarithmic reduction values of 6.38 (ie, 3 of 99 plates became nonsterile after being exposed to a 50 hPa pressure difference) and 6.07 (ie, 3 of the 99 plates became nonsterile after being exposed to a 70 hPa pressure difference) were obtained. Calculating an expected microbial challenge during transport and storage that requires barrier properties corresponding to a logarithmic reduction value of 5.83 and taking the sterility assurance level into account, we found that only the nonwoven pouches fulfilled the European standard EN 556-1.Conclusions.Using the data obtained in a microbial exposure test with a specified flow rate of a bacterial aerosol, we found that the effectiveness of the sterile barrier system against the actual microbial challenge can be examined and evaluated at the sterility assurance level of 10−6.

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