Electronic Journal of Polish Agricultural Universities (EJPAU) founded by all Polish Agriculture Universities presents original papers and review articles relevant to all aspects of agricultural sciences. It is target for persons working both in science and industry,regulatory agencies or teaching in agricultural sector. Covered by IFIS Publishing (Food Science and Technology Abstracts), ELSEVIER Science - Food Science and Technology Program, CAS USA (Chemical Abstracts), CABI Publishing UK and ALPSP (Association of Learned and Professional Society Publisher - full membership). Presented in the Master List of Thomson ISI.

Copyright © Wydawnictwo Akademii Rolniczej we Wroclawiu, ISSN 1505-0297

Siwiec T. 2007. THE EXPERIMENTAL VERIFICATION OF RICHARDSON-ZAKI LAW ON EXAMPLE OF SELECTED BEDS USED IN WATER TREATMENT, EJPAU 10(2), #05.
Available Online: http://www.ejpau.media.pl/volume10/issue2/abs-05.html

ABSTRACT

The paper presents and discusses the characteristics of various methods of determining the exponent for Richardson-Zaki [34] formula, which binds the flow velocity of rinsing water, sedimentation of bed grains in water, as well as bed porosity at various states of expansion. The characteristic of methods served for verification of their correlation with the results received from experimental tests, where the exponent was the degree of inclination in the relationship log V = n · log ε + log V_s, which is a logarithmic form of Richardson-Zaki formula. The tests were carried out for 8 minerals such as anthracite, barite, chalcedonite, diatomite, clinoptylolite, nevtraco, sand and pyrolusite. In order to make results more trustworthy, they were carried out for 10 fractions of each bed. It was shown that the formulas, from which the value of exponent n is commonly calculated, give results not differing much from one another, but considerably different from experimental ones, where the exponent was the degree of inclination of the above mentioned function. The results close to experimental ones were given by the formula containing sphericity of particles developed by Dharmajah and Cleasby [5]. Experimental results of testing enabled to develop the exponential functions describing the relationship of exponent n on Reynolds number in the state of free sedimentation.

Key words: backwashing filters, bed expansion, porosity, fluidization.

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Tadeusz Siwiec
Department of Civil Engineering and Geodesy,
Water Supply and Sewage Systems Section,
Warsaw Agricultural University, Poland
Nowoursynowska St. 159, 02-776 Warsaw, Poland
Phone: +48 22 59 35 161
email: Tadeusz_Siwiec@sggw.pl

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