Wyniki wyszukiwania - BazTech

1

Modelling of mass transport in watercourses at unsteady states

Bielski A.

Environment Protection Engineering

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2012

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Vol. 38, nr 3

159--173

EN

In terms of quality particularly difficult to describe are processes of mass exchange between different phases (e.g., atmospheric air-water, water-river sediment, water-algae, etc.). Whitman's model is most often used to describe the mass transport processes through the phase boundary. Theoretical analysis of the mass transfer process through the phase boundary showed that in unsteady states, the calculation results obtained from Whitman's model differ from the results obtained using the accurate diffusion model. These differences are due to the fact that concentration profiles in the direction of diffusion process change in time. Assumptions for Whitman's model do not include changes in the concentration distribution over time. Therefore, the correction factor was introduced to Whitman's model. The correction factor is defined as a parameter that multiplies a concentration derivative over time in the mass transport model. The correction factor can be used to estimate the effective diffusion coefficient of the substance that permeates from the aqueous phase to the sediment. The correction factor improves the degree of fit of the mass transport model to the measurement data. It can be used to estimate the effective turbulent diffusion coefficient from water phase to the sediment phase.

2

Modelling of mass transport in watercourses considering mass transfer between phases in unsteady states. Part I. Mass transfer process for periodic and aperiodic changes of concentration

Bielski A.

Environment Protection Engineering

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2011

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Vol. 37, nr 2

35-51

EN

A model most often used for the description of the processes of mass transport through phase boundaries is the model of Whitman. Results of calculations obtained using this model may occasionally considerably differ from the results obtained using diffusion models. Thus an attempt has been made to correct the model proposed by Whitman. The dynamics of the processes of mass transport from a liquid phase (river water) to a solid phase (layer of material in the river bottom) has been analysed. Several equations have been derived describing the rate of absorption with a chemical reaction and periodical changes of the concentration of the analysed substance. An attempt has been made to determine the relation between the concentration gradient and concentration at the phase boundary. In dynamic conditions, the concentration gradient at the phase boundary can be approximated by means of time dependence of a linear combination of concentration, delayed concentration, and concentration derivative at the phase boundary. Analysis of the dynamics of the absorption process with the chemical reaction enabled one to derive an equation describing the stream of the substance penetrating to the inside of the solid phase. Such equations may be used to determine the error generated by the film model of Whitman for the process of mass penetration.

3

Model transportu i dyfuzji w aspekcie zarządzania środowiskiem naturalnym

Przybycin Z.

Zeszyty Naukowe. Organizacja i Zarządzanie / Politechnika Śląska

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2006

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z. 35

149-157

PL

W artykule podjęto próbę zastosowania tez modelu transportu i dyfuzji do sterowania jakością powietrza atmosferycznego. Proponowany model umożliwia identyfikację sprawców zanieczyszczeń powietrza, a tym samym przypisanie im ekologicznych negatywnych skutków ich działalności. Zagadnienie sterowania jakością powietrza atmosferycznego sprowadzono do zagadnienia programowania liniowego.

EN

The paper presents the attemption to seploy so-named transportation and diffusion model to control of quality of the atmospheric air. The proposed model offers the possibility to identify pollution originators and to attribute them their activity results. The atmospheric air control problems comes to linear programming issues.

4

Double diffusivity from the distributed source on surface of a layer

Chaplia Y., Chernukha O.

Journal of Applied Computer Science

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2004

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Vol. 12, nr 2

45-64

EN

The solution has been obtained for the space problem of admixture diffusion by two ways allowing for mass transitions between the states under action of a constant circular source on a layer surface. This case has been compared with the solutions of the particular diffusion problems in a body with traps and diffusion in a medium with effective characteristics.