ISSN:0009-286X    

DOI:10.1002/cite.330680702

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractDue to the development of computers one may have the impression that the differences between methods of fluid mechanics and of chemical reaction engineering are diminished. But important differences survive, and their disregard can lead to misunderstandings. The main difference is the domination of the mass related view in reaction engineering and of the position related view in hydrodynamics. The analysis of the fundamentals result in the incorporation of the reaction kinetics and of the residence time distribution. Taking this into account, the dispersion model and the convection diffusion model are compared and the character of the axial dispersion coefficient and of the boundary conditions are discussed. It can be seen, that a direct transformation of hydrodynamics results is not possible. The simulation of the life history of molecules and particles offer an alternative for this.

ISSN:0009-286X    

DOI:10.1002/cite.330680703

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe sound pressure level measured at a distance of one meter is frequently used to assess the sound emission of a machine. The sound pressure level depends on the measuring distance, the directivity pattern, if any, of the machine and on the sound‐absorbing properties of the place of installation. Because it is a local field parameter it is not very suitable for ascertaining the sound emission of a machine. In contrast to, the sound power level is far more suitable because the influence mentioned earlier can be corrected and the value is reproducible for any random test condition. Generally, it is calculated from the results of sound pressure level measurements by application of the standardised enveloping surface method. Concerning sound intensity measurements a special probe allows ascertainment of the sound intensities directly on the enveloping surface. Despite an initially elaborate measuring technology, this method is in fact often faster and more exact than the enveloping surface method because it does not require subsequent correction to determine the sound power level. The benefits and drawbacks of sound pressure and sound intensity measurements are compared with each other on the basis of measurements on centrifuges directly related to practical operatio

ISSN:0009-286X    

DOI:10.1002/cite.330680704

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractIn the first part of this article an equation was derived for calculation of the specific interfacial are and the size distribution of bubbles in bubble flow. However, its application is limited to gas contents lower than 12%. At higher gas contents, large bubbles and gas plugs occur in the field of flow. These have a very low interfacial area per unit volume compared to small bubbles. Since large bubbles and gas plugs contain a large proportion of the gas in the flow, the overall interfacial area is reduced. In the present contribution, the gas content above which large bubbles and gas plugs occur is calculated. The results are subjected to experimental testing for vertical pipe flow. In addition, the volume fraction of the larger bubbles is calculated and the results verified experimentally by measurements in bubble columns. Subsequently, the specific enterfacial area with and without large bubbles is calculated for high gas contents. The results are in agreement with values measured for bubble columns and column plates.

ISSN:0009-286X    

DOI:10.1002/cite.330680705

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractIn spite of the fact that vortex formation, in unbaffled agitated vessels, is in most cases an undesirable phenomenon, many cases exist in chemical engineering where unbaffled systems can be used with greater effectivness than systems with baffles, at the same or even smaller energy consumption levels. Satisfactory results can also be obtained in unbaffled agitatated vessels without an air‐liquid interface. These facts, viewed in the light of energy problems in the chemical industry, show the current importance of comparative studies of baffled and unbaffled systems. In the present review article some characteristic cases from the fields of fluid dynamics, homogeneous distribution processes, suspensions, as well as mass‐transfer and heat‐transfer operations in baffled and unbaffled agitated vessels are presented and comparatively discussed in relation to their effecti

ISSN:0009-286X    

DOI:10.1002/cite.330680706

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

ISSN:0009-286X    

DOI:10.1002/cite.330680707

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

ISSN:0009-286X    

DOI:10.1002/cite.330680708

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

ISSN:0009-286X    

DOI:10.1002/cite.330680709

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

ISSN:0009-286X    

DOI:10.1002/cite.330680710

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

ISSN:0009-286X    

DOI:10.1002/cite.330680711

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY