Influence of Cowl on the Spatial Distribution of Oxygen in Semi-Aerobic Landfill

2012 ◽  
Vol 518-523 ◽  
pp. 3391-3395
Author(s):  
Ling Zhao ◽  
Chao Zhao
Keyword(s):  
Surface Layer ◽  
Spatial Distribution ◽  
Wind Speed ◽  
Flow Rate ◽  
Air Flow Rate ◽  
Wind Speeds ◽  
Aerobic Landfills ◽  
Different Climates ◽  
Oxygen Transmission ◽  
Oxygen Concentrations

To elevate the air flow rate in vent pipes of semi-aerobic landfill, promote oxygen transmit into waste and methane mitigation, a wind-driven cowl was fixed on one of the two semi-aerobic landfills’ vent pipe. With the aim of figuring out the influence of cowl on the spatial distribution of oxygen under different climates, wind speeds were set at 3 m/s, 5 m/s, 7 m/s and 0 m/s sequentially. Oxygen concentrations and temperatures were recorded once a week. Data from experimental results indicated that oxygen concentrations went up along with the height above the bottom of landfill after deducting the oxygen transported by leachate collection pipes. Average oxygen concentrations except the surface layer were 3.5%, 4.2%, 3.8%, 3.0% for S-A with cowl and 2.9%, 3.4%, 3.7%, 3.0% for S-A under the wind speeds of 3 m/s, 5 m/s, 7 m/s, 0 m/s, respectively. Meantime, the aerobic radius in S-A with cowl were 0.84 m, 1.01 m, 0.87 m, 0.62 m and 0.76 m, 0.84 m, 0.87 m, 0.65 m in S-A. The effect of the cowl on oxygen transmission maximized at the wind speed of 5 m/s. It is clearly that wind energy can be better used on enhancing the ventilation in vent pipe and expanding aerobic radius after application of cowl.

Quantification of NOX Emissions Based on Car MAX-DOAS Measurements over Beijing and Impacts of Wind Field

2020 ◽  
Author(s):  
Xinghong Cheng
Keyword(s):  
Spatial Distribution ◽  
Wind Speed ◽  
Wind Field ◽  
Meteorological Condition ◽  
Emission Rates ◽  
Wind Fields ◽  
Vertical Column ◽  
Wind Speeds ◽  
South Central ◽  
The Mean

<p>We carried out 14 days of Car MAX-DOAS experiments on the 6th Ring Rd of Beijing in January, September and October, 2014. The tropospheric vertical column densities (VCD) of NO<sub>2</sub> are retrieved and used to estimate the emissions of NO<sub>x</sub>. The offline LAPS-WRF-CMAQ model system is used to simulate wind fields by assimilation of observational data and calculate the NO<sub>2</sub> to NO<sub>x</sub> concentration ratios. The NO<sub>X</sub> emissions in Beijing for different seasons derived from Car MAX-DOAS measurements are compared with the multi-resolution emission inventory in China for 2012 (MEIC 2012), and impacts of wind field on estimated emissions and its uncertainties are also investigated. Results show that the NO<sub>2</sub> VCD is higher in January than other two months and it is typically larger at the southern parts of the 6th Ring Road than the northern parts of it. Wind field has obvious impacts on the spatial distribution of NO<sub>2</sub> VCD, and the mean NO<sub>2</sub> VCD with south wind at most sampling points along the 6th Ring Rd is higher than north wind. The journey-to-journey variation pattern of estimated NO<sub>X</sub> emissions rates (E<sub>NOX</sub>) is consistent with that of the NO<sub>2</sub> VCD, and E<sub>NOX </sub>is mainly determined by the NO2 VCD. In addition, the journey-to-journey E<sub>NOX</sub> in the same month is different and it is affected by wind speed, the ratio of NO<sub>2</sub> and NOx concentration and the decay rate of NO<sub>X</sub> from the emission sources to measured positions under different meteorological condition. The E<sub>NOX</sub> ranges between 6.46×10<sup>25</sup> and 50.05×10<sup>25</sup> molec s<sup>-1</sup>. The averaged E<sub>NOX</sub> during every journey in January, September and October are respectively 35.87×10<sup>25</sup>, 20.34×10<sup>25</sup>, 8.96×10<sup>25</sup> molec s<sup>-1</sup>. The estimated E<sub>NOX</sub> after removing the simulated error of wind speed and observed deviation of NO<sub>2</sub> VCD are found to be mostly closer to the MEIC 2012, but sometimes E<sub>NOX </sub>is lower or higher and it indicates that the MEIC 2012 might be overestimate or underestimate the true emissions. The estimated E<sub>NOX</sub> on January 27 and September 19 are obviously higher than other journeys in the same month because the mean NO<sub>2</sub> VCD and Leighton ratio during these two periods are larger, and corresponding wind speeds are smaller. Additionally, because south wind may affect the spatial distribution of mean NO<sub>2</sub> VCD in Beijing which is downwind of south-central regions of Hebei province with high source emission rates, the uncertainty of the estimated E<sub>NOX</sub> with south wind will be increased.</p>

scholarly journals Wavelet Analyses of Turbulence in the Hurricane Surface Layer during Landfalls

2010 ◽  
Vol 67 (12) ◽  
pp. 3793-3805 ◽  
Author(s):  
Ping Zhu ◽  
Jun A. Zhang ◽  
Forrest J. Masters
Keyword(s):  
Surface Layer ◽  
Wind Speed ◽  
Wind Stress ◽  
Surface Wind ◽  
Power Spectra ◽  
Substantial Effect ◽  
Vertical Transport ◽  
Transport Processes ◽  
Wind Speeds ◽  
Surface Wind Stress

Abstract Using wavelet transform (WT), this study analyzes the surface wind data collected by the portable wind towers during the landfalls of six hurricanes and one tropical storm in the 2002–04 seasons. The WT, which decomposes a time series onto the scale-time domain, provides a means to investigate the role of turbulent eddies in the vertical transport in the unsteady, inhomogeneous hurricane surface layer. The normalized WT power spectra (NWPS) show that the hurricane boundary layer roll vortices tend to suppress the eddy circulations immediately adjacent to rolls, but they do not appear to have a substantial effect on eddies smaller than 100 m. For low-wind conditions with surface wind speeds less than 10 m s−1, the contributions of small eddies (<236 m) to the surface wind stress and turbulent kinetic energy (TKE) decrease with the increase of wind speed. The opposite variation trend is found for eddies greater than 236 m. However, for wind speeds greater than 10 m s−1, contributions of both small and large eddies tend to level off as wind speeds keep increasing. It is also found that the scale of the peak NWPS of the surface wind stress is nearly constant with a mean value of approximately 86 m, whereas the scale of the peak NWPS of TKE generally increases with the increase of wind speed, suggesting the different roles of eddies in generating fluxes and TKE. This study illustrates the unique characteristics of the surface layer turbulent structures during hurricane landfalls. It is hoped that the findings of this study could enlighten the development and improvement of turbulent mixing schemes so that the vertical transport processes in the hurricane surface layer can be appropriately parameterized in forecasting models.

scholarly journals Influencing Mechanisms of a Crosswind on the Thermo-Hydraulic Characteristics of a Large-Scale Air-Cooled Heat Exchanger

Energies ◽  
2019 ◽  
Vol 12 (6) ◽  
pp. 1128
Author(s):  
Yanqiang Kong ◽  
Weijia Wang ◽  
Zhitao Zuo ◽  
Lijun Yang ◽  
Xiaoze Du ◽  
...  
Keyword(s):  
Heat Exchanger ◽  
Wind Speed ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Large Scale ◽  
Air Mass ◽  
Heat Rejection ◽  
Wind Speeds ◽  
Air Cooled Heat Exchanger

For the large scale air-cooled heat exchanger of a natural draft dry cooling system (NDDCS) in power plants, its thermo-flow characteristics are basically dominated by crosswinds. Unfortunately however, the detailed mechanisms of the crosswind effects have yet to be fully uncovered. Therefore, in this research, the local flow and heat transfer performances of the cooling deltas, which are also termed as the fundamental cells of the large-scale air-cooled heat exchanger, are specifically investigated with full consideration for the cell structure and the water-side temperature distribution at various wind speeds. A 3D CFD method with a realizable k-ε turbulence model, heat exchanger model, and porous media model is developed, and the accuracy and credibility of the numerical model are experimentally validated. With the numerical simulation, the overall 3D outlet air temperature of the large-scale air-cooled heat exchanger, and the corresponding local air velocity and temperature fields of the cooling deltas are qualitatively analyzed. Furthermore, the air-mass flow rate and heat rejection are also quantitatively studied at both the global and local views. The results depict that with an increase in the wind speed, the air mass flow rate and heat rejection will increase greatly for the frontal deltas; however, they will drop dramatically for the middle-front deltas. As for the middle- as well as the middle-rear deltas, the thermo-flow performances vary markedly at various wind speeds, which behave in the most deteriorated manner at a wind speed of 12 m/s. The rear deltas show the best thermo-flow performances at a wind speed of 12 m/s, but the worst at 16 m/s. A detailed analysis of the variable fields for each cooling delta may contribute to the performance improvement of the large-scale air-cooled heat exchanger of NDDCS.

scholarly journals Seasonality in onshore normalized wind profiles above the surface layer

2010 ◽  
Vol 4 (1) ◽  
pp. 57-62 ◽  
Author(s):  
J. N. Nissen ◽  
S.-E. Gryning
Keyword(s):  
Surface Layer ◽  
Wind Speed ◽  
Marine Boundary Layer ◽  
Mesoscale Model ◽  
Atmospheric Stability ◽  
Relative Difference ◽  
Stability Class ◽  
Surface Stability ◽  
Wind Speeds ◽  
Seasonal Signal

Abstract. This work aims to study the seasonal difference in normalized wind speed above the surface layer as it is observed at the 160 m high mast at the coastal site Høvsøre at winds from the sea (westerly). Normalized and stability averaged wind speeds above the surface layer are observed to be 20 to 50% larger in the winter/spring seasons compared to the summer/autumn seasons at winds from west within the same atmospheric stability class. A method combining the mesoscale model, COAMPS, and observations of the surface stability of the marine boundary layer is presented. The objective of the method is to reconstruct the seasonal signal in normalized wind speed and identify the physical process behind. The method proved reasonably successful in capturing the relative difference in wind speed between seasons, indicating that the simulated physical processes are likely candidates to the observed seasonal signal in normalized wind speed.

scholarly journals Air Flow Rate in Leachate Collection Pipe of Semi-Aerobic Landfills

1995 ◽  
Vol 6 (4) ◽  
pp. 129-138 ◽  
Author(s):  
Youngkyu KIM ◽  
Toshihiko MATSUTO ◽  
Yasumasa TOJO ◽  
Nobutoshi TANAKA
Keyword(s):  
Flow Rate ◽  
Air Flow ◽  
Air Flow Rate ◽  
Leachate Collection ◽  
Aerobic Landfills

scholarly journals Air Flow Rate in Leachate Collection Pipe of Semi-Aerobic Landfills

1997 ◽  
Vol 8 (1) ◽  
pp. 1-8 ◽  
Author(s):  
Nobutoshi Tanaka ◽  
Toshihiko Matsuto ◽  
Youngkyu Kim
Keyword(s):  
Flow Rate ◽  
Air Flow ◽  
Air Flow Rate ◽  
Leachate Collection ◽  
Aerobic Landfills

SHAPING OF AN AUTONOMOUS POWER SYSTEM FOR GUARANTEED POWER SUPPLY WITH THE PREDOMINANCE WIND ENERGY

2018 ◽  
pp. 28-50
Author(s):  
S. G. Ignatiev ◽  
S. V. Kiseleva
Keyword(s):  
Energy Storage ◽  
Wind Speed ◽  
Wind Energy ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Energy Demand ◽  
Diesel Generator ◽  
Average Wind Speed ◽  
Wind Speeds ◽  
Average Wind

Optimization of the autonomous wind-diesel plants composition and of their power for guaranteed energy supply, despite the long history of research, the diversity of approaches and methods, is an urgent problem. In this paper, a detailed analysis of the wind energy characteristics is proposed to shape an autonomous power system for a guaranteed power supply with predominance wind energy. The analysis was carried out on the basis of wind speed measurements in the south of the European part of Russia during 8 months at different heights with a discreteness of 10 minutes. As a result, we have obtained a sequence of average daily wind speeds and the sequences constructed by arbitrary variations in the distribution of average daily wind speeds in this interval. These sequences have been used to calculate energy balances in systems (wind turbines + diesel generator + consumer with constant and limited daily energy demand) and (wind turbines + diesel generator + consumer with constant and limited daily energy demand + energy storage). In order to maximize the use of wind energy, the wind turbine integrally for the period in question is assumed to produce the required amount of energy. For the generality of consideration, we have introduced the relative values of the required energy, relative energy produced by the wind turbine and the diesel generator and relative storage capacity by normalizing them to the swept area of the wind wheel. The paper shows the effect of the average wind speed over the period on the energy characteristics of the system (wind turbine + diesel generator + consumer). It was found that the wind turbine energy produced, wind turbine energy used by the consumer, fuel consumption, and fuel economy depend (close to cubic dependence) upon the specified average wind speed. It was found that, for the same system with a limited amount of required energy and high average wind speed over the period, the wind turbines with lower generator power and smaller wind wheel radius use wind energy more efficiently than the wind turbines with higher generator power and larger wind wheel radius at less average wind speed. For the system (wind turbine + diesel generator + energy storage + consumer) with increasing average speed for a given amount of energy required, which in general is covered by the energy production of wind turbines for the period, the maximum size capacity of the storage device decreases. With decreasing the energy storage capacity, the influence of the random nature of the change in wind speed decreases, and at some values of the relative capacity, it can be neglected.

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