The Determination of The Mixing Height: An Extended Version of The Safe_Air Dispersion Model

2006 ◽  
pp. 719-720
Author(s):  
Emilia Georgieva ◽  
Elisa Canepa ◽  
Corrado F. Ratto
Keyword(s):  
Dispersion Model ◽  
Extended Version ◽  
Mixing Height

Chapter 20 Review and intercomparison of operational methods for the determination of the mixing height

2002 ◽  
pp. 569-613 ◽  
Author(s):  
Petra Seibert ◽  
Frank Beyrich ◽  
Sven-Erik Gryning ◽  
Sylvain Joffre ◽  
Alix Rasmussen ◽  
...  
Keyword(s):  
Mixing Height ◽  
Operational Methods

scholarly journals Evaluation method of single blow experiment for the determination of heat transfer coefficient and dispersive Peclet number

2015 ◽  
Vol 36 (4) ◽  
pp. 3-24 ◽  
Author(s):  
Wilfried Roetzel ◽  
Chakkrit Na Ranong
Keyword(s):  
Heat Exchangers ◽  
Peclet Number ◽  
Numerical Evaluation ◽  
Evaluation Method ◽  
Dispersion Model ◽  
Tracer Experiment ◽  
Effective Number ◽  
Péclet Number ◽  
Modified Method

Abstract An evaluation method is developed for single blow experiments with liquids on heat exchangers. The method is based on the unity Mach number dispersion model. The evaluation of one experiment yields merely one equation for the two unknowns, the number of transfer units and the dispersive Peclet number. Calculations on an example confirm that one single blow test alone cannot provide reliable values of the unknowns. A second test with a liquid of differing heat capacity is required, or a tracer experiment for the measurement of the Peclet number. A modified method is developed for gases. One experiment yields the effective number of transfer units and approximate values of the two unknowns. The numerical evaluation of calculated experiments demonstrates the applicability of the evaluation methods.

scholarly journals Determination of an effective trace gas mixing height by differential optical absorption spectroscopy (DOAS)

2009 ◽  
Vol 2 (4) ◽  
pp. 1663-1692 ◽  
Author(s):  
B. Zhou ◽  
S. N. Yang ◽  
S. S. Wang ◽  
T. Wagner
Keyword(s):  
Trace Gases ◽  
Mixing Layer ◽  
Correlation Coefficients ◽  
Trace Gas ◽  
Optical Absorption Spectroscopy ◽  
Gas Mixing ◽  
Mixing Height ◽  
Free Atmosphere ◽  
Layer Height

Abstract. A new method for the determination of the Mixing layer Height (MH) by the DOAS technique is proposed in this article. The MH can be retrieved by a combination of active DOAS and passive DOAS observations of atmospheric trace gases; here we focus on observations of NO2. Because our observations are sensitive to the vertical distribution of trace gases, we refer to the retrieved layer height as an ''effective trace gas mixing height'' (ETMH). By analyzing trace gas observations in Shanghai over one year (1017 hourly means in 93 days in 2007), the retrieved ETMH was found to range between 0.1 km and 2.8 km (average is 0.78 km); more than 90% of the measurements yield an ETMH between 0.2 km and 2.0 km. The seasonal and diurnal variation of the ETMH shows good agreement with mixing layer heights derived from meteorological observations. We investigated the relationship of the derived ETMH to temperature and wind speed and found correlation coefficients of 0.65 and 0.37, respectively. Also the wind direction has an impact on the measurement to some extent. Especially in cases when the air flow comes from highly polluted areas and the atmospheric lifetime of NO2 is long (e.g. in winter), the NO2 concentration at high altitudes over the measurement site can be enhanced, which leads to an overestimation of the ETMH. Enhanced NO2 concentrations in the free atmosphere and heterogeneity within the mixing layer can cause additional uncertainties. Our method could be easily extended to other species like e.g. SO2, HCHO or Glyoxal. Simultaneous studies of these molecules could yield valuable information on their respective atmospheric lifetimes.

Modelling of Flow of a Liquid in Apparatus with Mobile Packing: Dispersion Model

1993 ◽  
Vol 58 (9) ◽  
pp. 2047-2058
Author(s):  
Zdeněk Palatý
Keyword(s):  
Differential Equation ◽  
Numerical Integration ◽  
Residence Time ◽  
Mean Residence Time ◽  
Peclet Number ◽  
Dispersion Model ◽  
Tracer Concentration ◽  
Optimization Of Parameters ◽  
Determination Of Parameters

The paper deals with determination of parameters of a dispersion model used for describing the flow of liquid on a plate with mobile packing in the region of gas velocities up to 1.5 m s-1. The parameters of the model - the diffusion Peclet number and mean residence time of liquid - were determined from the nonideal input impulse of tracer concentration and its response by the method of numerical integration of differential equation with subsequent optimization of parameters. The results of measurements are presented graphically and in the form of criterion equations.

Determination of the aeration capacity of bubble columns by dynamic method. The influence of axial dispersion and of the start-up period

1979 ◽  
Vol 44 (9) ◽  
pp. 2583-2597 ◽  
Author(s):  
Václav Linek ◽  
Jiří Stejskal ◽  
Jiří Sinkule ◽  
Václav Vacek
Keyword(s):  
Dynamic Method ◽  
Dispersion Model ◽  
Oxygen Electrode ◽  
Axial Dispersion ◽  
Bubble Columns ◽  
Oxygen Probe ◽  
Start Up ◽  
Axial Dispersion Model ◽  
Aeration Capacity

A dynamic method for the determination of volumetric mass transfer coefficient of oxygen, kLa, in bubble columns using an oxygen electrode was derived on the basis of a liquid phase axial dispersion model The influence of aeration startup was studied assuming that the kLa value is position and time dependent. The conditions are defined under which the influence of aeration startup and of axial mixing of the liquid upon the steady state kLa value is negligible. A critical assessment has been made of various methods proposed for evaluation of oxygen probe responses.

Simultaneous determination of dispersion model parameters and local thickness of thin films by imaging spectrophotometry

2015 ◽  
Vol 350 ◽  
pp. 149-155 ◽  
Author(s):  
David Nečas ◽  
Jiří Vodák ◽  
Ivan Ohlídal ◽  
Miloslav Ohlídal ◽  
Abhijit Majumdar ◽  
...  
Keyword(s):  
Thin Films ◽  
Simultaneous Determination ◽  
Dispersion Model ◽  
Model Parameters

scholarly journals The effect of electronic excitation on London dispersion

2018 ◽  
Vol 96 (7) ◽  
pp. 730-737 ◽  
Author(s):  
Xibo Feng ◽  
Alberto Otero-de-la-Roza ◽  
Erin R. Johnson
Keyword(s):  
Density Functional ◽  
Electronic Excitation ◽  
Organic Dyes ◽  
Dispersion Model ◽  
Dispersion Energy ◽  
Dispersion Coefficients ◽  
Light Emitting ◽  
Molecular Dispersion ◽  
London Dispersion

Atomic and molecular dispersion coefficients can now be calculated routinely using density-functional theory. In this work, we present the first determination of how electronic excitation affects molecular C6 London dispersion coefficients from the exchange-hole dipole moment (XDM) dispersion model. Excited states are typically found to have larger dispersion coefficients than the corresponding ground states, due to their more diffuse electron densities. A particular focus is both intramolecular and intermolecular charge-transfer excitations, which have high absorbance intensities and are important in organic dyes, light-emitting diodes, and photovoltaics. In these classes of molecules, the increase in C6 for the electron-accepting moiety is largely offset by a decrease in C6 for the electron-donating moiety. As a result, the change in dispersion energy for a chromophore interacting with neighbouring molecules in the condensed phase is minimal.

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