6 replies to this topic

[rosa]

hi friends,

I want to calculate Reynolds number in a packed bed.would you please introduce me a suitable sources?
your cooporation would be appreciated.

Kind regards,
Rosa

[P.K.Rao]

Rosa,

Please visit the following sites in this respect.

http://www.processas...imen/dn_rey.htm

http://www.efunda.co...lc_reynolds.cfm

All the best

P.K.Rao

[Nirav]

Hello,

For "PACKED BED", Reynold's number can be calculated online at following link.

http://www.mycalcula...jmm/chem08.html

Regards,

[Art Montemayor]

P. K.:

The query is for determining the Reynolds Number in a packed bed (for example, in an adsorber or a packed bed reactor) - not in a pipe. Therefore, your response does not apply to the query. The two are totally different in the calculation method and the specific equations. One has to be very careful and analyze the application. The Reynolds Number applies to a variety of situations, but the application and the configuration of the flow determines how the concept is applied.

Nirav:

Great response. I believe it is right on the button as to the application. The Ergun equation is the equation of choice in doing packed bed pressure drops. I have used it quite a lot in designing adsorber beds and it is the recommended relationship used by ALCOA for their Activated Alumina adsorbents.

I notice that the site you lead us to cites the following reference for their application of the equation:

Coker, AK; Fortran Programs For Chemical Process Design, Analysis & Simulation; Gulf Publ. Co, Houston, 1995

Coker wrote a book that was on to something sorely needed in the process engineeering arena and he came close to contributing something of worth. However, this particular book turned out to be a pile of trash - filled with gross errors, flawed equations, enough errata to fill a room, and the book's index and formatting are a shame to look at. Coker is a brilliant academic with a progressive look at how to teach engineering. However, on this book he or Gulf Publishing really dropped the ball. The material is basically there and the subject matter is vital and useful to all engineers. However, the way it was handled and treated leaves one with a bad taste in one's mouth. I have found so many errors in this reference that I would be very suspicious of using it without a detailed and accurate check of all the equations and the methodology used. I caution any engineer who might be attracted to this book (because the attraction is only a natural one) and recommend that the algorithm and the related equations be scrutinized very carefully.

Rosa:

You don't state what type, size, and application of packed bed you are looking at, but I assume that Nirav gave you what you need. The type, size, and shape of the packing play a factor in determining the pressure drop - as well as the assumption that the bed will remain perfectly static. I always try to employ downflow in order to ensure a stable bed during flow. If you have to employ upflow, then you have to design and use bed hold-downs and restraints, taking into consideration that your bed will shrink in size during use for various reasons. In a real application, this can cause a lot of operational grief.

[P.K.Rao]

Art,

Thanks for pointing out my mistake.

P.K.Rao

[Profe]

Hi Rosa

Attached I send you an article about your request

Review it completely to have a greater understanding of the subject.

Good luck

[Profe]

Hi again Rosa

Attached I send you another article about your request:

By the way Rosa, for Reynolds in Packed bed, you find about it, in Perry "Chemical Engineers Handbook"
by Robert H. Perry & Don W. Green. Chapter 6 Fluid and Particle Dynamics pp.6-38, ...., 6-40. Subject BEDS OF SOLIDS
And Perry "Chemical Engineers Handbook" Fifth edition by Robert H. Perry & Cecil H. Chilton Chapter 5 pp. 5-52, ...., 5-54

Adittionaly Rosa, If you read Spanish, you can review "Problemas de Ingeniería Química" by Joaquín Ocon Garcia & Gabriel Tojo Barreiro. Tomo 2 Chapter 10 if you get this book.

Good luck