scholarly journals Numerical Research on the Mixture Mechanism of Polluted and Fresh Air at the Staggered Tunnel Portals

2018 ◽  
Vol 8 (8) ◽  
pp. 1365 ◽  
Author(s):  
Xin Zhang ◽  
Tianhang Zhang ◽  
Kai Zhu ◽  
Zhiyi Huang ◽  
Ke Wu
Keyword(s):  
Ventilation System ◽  
Flow Characteristics ◽  
Simulation Method ◽  
System Construction ◽  
Mixing Ratio ◽  
Air Velocity ◽  
Factors Affecting ◽  
Longitudinal Ventilation ◽  
Air Mixing ◽  
The Impact

In longitudinal ventilation, circulating air is formed in portals for closely spaced twin tunnels, which causes mixing between the polluted air exhausted from one tunnel and the fresh air flow of another tunnel, thus leading to the rising costs of ventilation system construction and operation. In this study, for the closely spaced tunnel with staggered inlet and outlet, the computational fluid dynamics (CFD) numerical simulation method was adopted to reveal flow characteristics of the circulating air as well as variation rules of the circulating air mixing ratio φc with tunnel structure and operation parameters. Results show that both reducing inlet air velocity and increasing outlet air velocity and lateral distance can reduce the impact of the negative-pressure zone at the tunnel entrance on the jet flow structure at the tunnel exit, thus weakening the circulating air. When the inlet is placed behind or aligned with the outlet (staggered distance ∆l ≤ 0), φc will increase linearly along with the increase of staggered distance; when the inlet is placed before the outlet (∆l > 0), φc will first increase and then decrease with the increase of staggered distance. An expression to predict circulating air mixing ratio was created by sections. The predictions show a good correlation with the measurements and indicate that the front slope gradient of the tunnel portal is also one of the factors affecting the circulating air mixing ratio.

CFD Investigation for Indoor Environment of a District Standard Room in Jinan City

2014 ◽  
Vol 548-549 ◽  
pp. 1706-1711
Author(s):  
Dong Yang ◽  
Qing Mei Wen ◽  
Cong Ju Zhang ◽  
Xue Ting Liu ◽  
Shi Jun Wei
Keyword(s):  
Composite System ◽  
Ventilation System ◽  
Simulation Method ◽  
Displacement Ventilation ◽  
Air Velocity ◽  
Vertical Temperature ◽  
Airflow Velocity ◽  
Indoor Airflow ◽  
Radiant Cooling ◽  
Air Speed

This paper introduces the principle and characteristics of roof radiant cooling and displacement ventilation system, using numerical simulation method, the indoor airflow velocity and temperature field of the typical bedroom which uses the composite system in Ji'nan City under the different supply air velocity was calculated. The experimental results show that when the air temperature is 295.15K, to keep the indoor vertical temperature less than 3 °C, air speed should be greater than 0.1m/s and less than or equal to 0.3m/s, to provide reference for the application of roof radiant cooling and displacement ventilation system.

scholarly journals Model of Prediction of Gas Emission based on Gas Content Uncertainty in Coal Mine using Geostatistical Simulation and Monte Carlo Method

2021 ◽  
Author(s):  
Shokofe Rahimi ◽  
Majid Ataee-pour ◽  
Hasan Madani
Keyword(s):  
Monte Carlo ◽  
Coal Seam ◽  
Ventilation System ◽  
Prediction Method ◽  
Simulation Method ◽  
Worker Safety ◽  
Gas Content ◽  
Geostatistical Simulation ◽  
Gas Emission ◽  
Factors Affecting

Abstract It is very difficult to predict the emission of coal gas before the extraction, because it depends on various geological, geographical and operational factors. Gas content is a very important parameter for assessing gas emission in the coal seam during and after the extraction. Large amounts of gas released during the mining cause concern about adequate airflow for the ventilation and worker safety. Hence, the performance of the ventilation system is very important in an underground mine. In this paper, the gas content uncertainty in a coal seam is first investigated using the central data of 64 exploratory boreholes. After identifying the important coal seams in terms of gas emission, the variogram modeling for gas content was performed to define the distribution. Consecutive simulations were run for the random evaluation of gas content. Then, a method was proposed to predict gas emission based on the Monte Carlo random simulation method. In order to improve the reliability and precision of gas emission prediction, various factors affecting the gas emission were investigated and the main factors determining the gas emission were identified based on a sensitivity analysis on the mine data. This method produced relative and average errors of 2% and 0.57%, respectively. The results showed that the proposed model is accurate enough to determine the amount of emitted gas and ventilation. In addition, the predicted value was basically consistent with the actual value and the gas emission prediction method based on the uncertainty theory is reliable.

scholarly journals Air flow characteristics of a room with air vortex diffuser

2018 ◽  
Vol 240 ◽  
pp. 02002 ◽  
Author(s):  
Marek Borowski ◽  
Marek Jaszczur ◽  
Daniel Satoła ◽  
Michał Karch
Keyword(s):  
Air Flow ◽  
Ventilation System ◽  
Flow Characteristics ◽  
Comfort Level ◽  
Translational Velocity ◽  
Comfort Zone ◽  
Air Velocity ◽  
Velocity Decay ◽  
Different Diameters ◽  
Comfort Criteria

The air diffuser is a very important component of any ventilation system, and the comfort level of ventilated space occupants depend among many other factors on properly designed and choice of diffusers. At present a large number of diffusers are produced to meet a different kind of requirements. One of the most efficient and very popular types of the diffuser is the vortex diffuser in which air flow has angular as well as translational velocity components. This paper investigates experimentally airflow characteristics of vortex ceiling diffuser and its effect on airflow in a ventilated space. Two thermal comfort criteria namely: mean age of the air and ventilation effectiveness have been used to predict the comfort zone inside the room. Effect of supply air velocity on the flow field is investigated and hence the on comfort and energy consumption. The results show that significant amount of energy can be saved by using vortex diffuser in reference to the other diffusers type. The values of the velocity decay coefficient were compared for different diameters of vortex diffuser.

scholarly journals The Airflow Reversal Law in Ventilation System after Coal and Gas Outburst in Tunneling Roadway

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Junhong Si ◽  
Yiqiao Wang ◽  
Genyin Cheng ◽  
Lin Li ◽  
Yitian Shao ◽  
...  
Keyword(s):  
Ventilation System ◽  
Simulation Method ◽  
Coal And Gas Outburst ◽  
Air Velocity ◽  
Relative Variation ◽  
Gas Concentration ◽  
Gas Outburst ◽  
Cubic Polynomial ◽  
The Relationship ◽  
Topology Graph

Considering the coal and gas outburst phenomenon in the mining space, this paper analyzes the main characteristics of coal and gas outburst accidents, defines the outburst airflow reversal degree, and constructs a simplified topology graph of tunneling ventilation system, while the air door is not destroyed. Using the numerical simulation method, this paper elaborates on the relationship between the outburst pressure and airflow reversal degree. The results indicate that the inlet pressure increases to 264 hPa and the outlet pressure increases to 289 hPa when the outburst pressure increases from 1 hPa to 1 MPa, and the relative variation coefficient of pressure decreases from 1501.5 to 1.62 in the inlet of return airway and decreases from 2002 to 1.65 in the outlet of return airway. Furthermore, the air velocity decreases from −1.38 to −284.44 m/s in the inlet and increases from 3.10 to 297.38 m/s in the outlet. Moreover, the gas concentration of the inlet and outlet in return airway increases rapidly with the increase of outburst pressure. When the outburst pressure is greater than 0.15 MPa, the gas concentration will be over 98% in tunneling ventilation system. This paper also finds out a cubic polynomial relationship existing between the reversal degree and the outburst pressure. It provides the prediction of coal and gas outburst and serves as a guidance in case mine ventilation disturbances occur.

scholarly journals SOSIALISASI PENTINGNYA TIDAK MEMBUANG AIR BESAR DI SUNGAI (STOP BABS) DI DESA GAMPANG KECAMATAN PRAMBON

2017 ◽  
Vol 1 (1) ◽  
pp. 43-48
Author(s):  
Shoim Anwar
Keyword(s):  
Direct Contact ◽  
River Flow ◽  
Flow Characteristics ◽  
Influential Factor ◽  
Factors Affecting ◽  
Intentional Behavior ◽  
The People ◽  
The One ◽  
The Impact ◽  
The Village

Sanitation is the one component of environmental health as intentional behavior for cultivate human hygiene to prevent direct contact with dirt and other hazardous waste material, with the hope to maintain and improve human health. This is because, the environment may play a direct cause influential factor in supporting the outbreak of disease and as factors affecting the course of the disease. All feces is a medium as breeding and seed base of infectious diseases. The impact of the disease is most often caused by defecation to the river is the widespread bacterium Escherichia coli, which can cause diarrhea. After that could be dehydrated, and because of the condition of human body’s down then get other diseases. The river is a very important source of water to support human’s life. Dynamism watersheds are influenced by the weather, river flow characteristics and human behaviour of the people who live around the river banks. As a result of effluent from people behaviour causes disturbance to the ecosystem of the river flow. Starting from the non-fulfillment of water quality 3B standarts (colorless, odorless and non-toxic), reduced numbers of fish and water animals, the emergence of a rundown neighborhood until the emergence of health problems and others, therefore, to KKN-PPM in the field of Environmental Sanitation and Supply water in the village Easy in Subdisrtict Prambon, Sidoarjo, the program will be made by "socialization of Great Importance Not Throw water on the River (STOP BABS)".

scholarly journals Experimental determination of tunnel ventilation axial ducted fan performance

2016 ◽  
Vol 20 (1) ◽  
pp. 209-221 ◽  
Author(s):  
Milan Sekularac
Keyword(s):  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Ventilation System ◽  
Flow Characteristics ◽  
Pollutant Removal ◽  
Reynolds Stresses ◽  
Scaled Model ◽  
Tunnel Ventilation ◽  
Longitudinal Ventilation ◽  
Traffic Tunnel

To investigate traffic tunnel ventilation flows, a scaled model of a traffic tunnel with longitudinal ventilation system based on ducted fans is used. Flows in tunnels are influenced by tunnel geometry, fan characteristics, ventilation operation scenario, vehicle traffic, atmospheric factors, etc. To analyze flow fields of tunnels in detail, knowledge of tunnel jet-fan properties and turbulent flow characteristics at the fan exit are required, and can be used as input data for CFD boundary conditions of tunnel flow computation. For this purpose experimental measurements were done using the hot wire anemometry technique. The obtained results, trough ensemble-averaged and time averaged profiles of all velocity components, turbulence intensity, turbulent kinetic energy, integral flow length scales, available Reynolds stresses, Turbulent kinetic energy production rates and the fan thrust performance, are presented. These data allow us to analyze in more detail the influence of fan flow on energy and pollutant removal efficiencies of the tunnel ventilation and to evaluate accuracy of CFD studies on fan improvements.

Multistage Self-Priming Pump Performance Simulation & Test Research

2014 ◽  
Vol 651-653 ◽  
pp. 780-783
Author(s):  
Gao Feng Liang ◽  
Qiang Gao
Keyword(s):  
Design Theory ◽  
Flow Characteristics ◽  
Internal Flow ◽  
Simulation Method ◽  
Hydraulic Performance ◽  
Operating Conditions ◽  
Centrifugal Pumps ◽  
Pump Design ◽  
Multi Stage ◽  
The Impact

Currently the application of traditional centrifugal pump design theory to develop the multi-stage centrifugal pumps is very mature, but the factor of affecting hydraulic performance of centrifugal self-priming pump is still unclear. In this paper, using CFD method to simulate the hydraulic performance of the multistage self-priming pump in different operating conditions, and get the performance prediction curve. The simulation results were compared with experimental data, the result shows that simulation method can accurately predict the performance and internal flow characteristics of multi-stage self-priming pump. The impact on the hydraulic performance by water-keeper chamber and the gas-liquid separation chamber is very limited. The self-priming components can provide a better hydraulic performance. This will be as a reference for the design of self-priming pump.

scholarly journals An airborne amplitude-modulated 1.57 μm differential laser absorption spectrometer: simultaneous measurement of partial column-averaged dry air mixing ratio of CO<sub>2</sub> and target range

2013 ◽  
Vol 6 (2) ◽  
pp. 387-396 ◽  
Author(s):  
D. Sakaizawa ◽  
S. Kawakami ◽  
M. Nakajima ◽  
T. Tanaka ◽  
I. Morino ◽  
...  
Keyword(s):  
Target Range ◽  
Mixing Ratio ◽  
Validation Data ◽  
Lower Altitude ◽  
Dry Air ◽  
Laser Absorption ◽  
Air Mixing ◽  
The Difference ◽  
The Impact ◽  
Absorption Spectrometer

Abstract. Simultaneous measurements of the partial column-averaged dry air mixing ratio of CO2 (XCO2) and target range were demonstrated using airborne amplitude-modulated 1.57 μm differential laser absorption spectrometer (LAS). The LAS system is useful for discriminating between ground and cloud return signals and has a demonstrated ability to suppress the impact of integrated aerosol signals on atmospheric CO2 measurements. A high correlation coefficient (R) of 0.987 between XCO2 observed by LAS and XCO2 calculated from in situ measurements was obtained. The averaged difference in XCO2 obtained from LAS and validation data was within 1.5 ppm for all spiral measurements. An interesting vertical profile was observed for both XCO2LAS and XCO2val, in which lower altitude CO2 decreases compared to higher altitude CO2 attributed to the photosynthesis over grassland in the summer. In the case of an urban area where there are boundary-layer enhanced CO2 and aerosol in the winter, the difference of XCO2LAS to XCO2val is a negative bias of 1.5 ppm, and XCO2LAS is in agreement with XCO2val within the measurement precision of 2.4 ppm (1 SD).

scholarly journals An airborne amplitude-modulated 1.57 μm differential laser absorption spectrometry: simultaneous measurement of partial column-averaged dry air mixing ratio of CO<sub>2</sub> and target range

2012 ◽  
Vol 5 (4) ◽  
pp. 4851-4880
Author(s):  
D. Sakaizawa ◽  
S. Kawakami ◽  
M. Nakajima ◽  
T. Tanaka ◽  
I. Morino ◽  
...  
Keyword(s):  
Absorption Spectrometry ◽  
Lower Atmosphere ◽  
Target Range ◽  
Mixing Ratio ◽  
Validation Data ◽  
Lower Altitude ◽  
Dry Air ◽  
Laser Absorption ◽  
Air Mixing ◽  
The Impact

Abstract. Simultaneous measurements of the partial column-averaged dry air mixing ratio of CO2 (q) and target range were demonstrated using airborne amplitude-modulated 1.57 μm differential laser absorption spectrometry (LAS). The LAS system is useful for discriminating between ground and cloud return signals and has a demonstrated ability to suppress the impact of integrated aerosol signals on differential absorption optical depth (Δτ) measurements. A high correlation coefficient (R) of 0.99 between Δτ observed by LAS and Δτ calculated from in-situ measurements of CO2 was obtained. The averaged difference in q obtained from LAS (qLAS) and validation data (qval) was within 1.5 ppm for all spiral measurements. A significant profile was observed for both qLAS and qval, in which lower altitude CO2 decreases compared to higher altitude CO2 attributed to the photosynthesis over grassland in the summer. In the case of an urban area where CO2 and aerosol are highly distributed in the lower atmosphere in the winter, the difference of qLAS to qval is −1.5 ppm, and evaluated qLAS is in agreement with qval within the measurement precision of 2.4 ppm (1σ).

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