×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Relationship between Reynolds number and plug flow

Relationship between Reynolds number and plug flow

Relationship between Reynolds number and plug flow

(OP)
I have a situation where I have a 3" pipe and want to reach a certain residence time in the pipe.  The fluid is nylon at approximately 300 poise.  I've done an experiment and found that I get channeling.  My pipe length is 36" and flow is about 16 lb/hr.  I can get 40 minutes RT when filling an empty pipe, but doing a tracer study, I found that it is only 20 minutes, which suggests channeling.  I am wondering if there is too small of a Reynolds number to achieve true plug flow.  Is there some correlation there?  What are the "rules of thumb" for PFR's?  

The pipe is vertical and filling from the bottom.  Should I try using a static mixer?

RE: Relationship between Reynolds number and plug flow

Suggest you read a chemical reaction engineering text such as Levenspiel or Fogler to refresh your memory.  

Plug flow doesn't happen until you have not just turbulent flow, but fully developed turbulent flow (Re > 10,000).  Doubtful that you're going to get Reynolds numbers that high with a viscosity of 30,000 cP at anything approximating a reasonable pressure drop.

You NEED static mixers, and even single tube static mixers may not be enough.

RE: Relationship between Reynolds number and plug flow

As nylon is a non-newtonian fluid (viscoelastic), I guess you cannot use the reynolds as you would do for a newtonian fluid? -or can you assume that the 'flow conditions' are similar to those of a newtonian fluid and thus use the reynolds as we know it?

RE: Relationship between Reynolds number and plug flow

(OP)
Ah yes...  Fogler...  His book is an argument for another day.

Thanks for the insight.  I doubt I can realistically get the Reynold's number over 1 with nylon and my equipment.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources