hello

i want to do RTD studies on reactor for that i have a created an Additional Variable "RDT" with unit [s]and volumetric vaiable type . RDT is set "0" at all inlet.

Then create a subdomain "RDT sub" over all and impement a source for RTD with 1 [s/s].

my question is how do to see residence time distribution in CFX post and how will we get RTD curve

with regards user

Hi,

Similer as doing experiment, you need to input tracer('RDT' as you created) (either step or pulse input) from inlet and monitor the change of concentrations at outlet. You will see the RTD curve in solver monitoring window.

The steady state solution as you described will not give you a tracer curve.

Search 'tracer' in official CFX forum, you will find more detailed information.

Regards!

Jianping

hello zhang

thanks for suggestions,now i got RTD curve is it possible to get dispersion coefficient from residence time distribution

can u guide me How to get dispersion coeffiecient from RTD study

thanks in advance with regards

Hi,

I do not have experience of doing that, however I think you have to have some experiemntal RTD curves(for validation purpose) as well for calculating dispersion coefficient.

To calculate dispersion coefficient, I believe you can easily find examples in most of reactor theory books.

Regards!

Jianping

hi zhang

thanks for suggestions

best regards

Hello friend,

I am a student of M.E chemical engineering, BITS-Pilani, INDIA. I am working on RTD prediction in an ideal plug flow reactor using fluent. I don't know how to inject tracer in CFD. I would be grateful to you if you can help me in this regard.

These are the inputs I have given. Are these specifications correct?

Models-viscous-laminar. 2-D unsteady state, implicit formulation. Length of PFR=50 cm. Diameter=5 cm. Materials inside the reactor=Water, Toulene. Tracer used: Toulene. Mass flow inlet of toluene=0.023 kg/s. Mass flow inlet of water=0.039 kg/s. X-velocity of tracer=0.0135 m/s. Delta t=1 s. Total no. of time steps=840 s.

I would be very much grateful to you Jianping Zhang if you can help me in this regard. Please send the procedure of predicting RTD in Fluent if you can.Also is there any provision of concentartion input in fluent?

Awaiting for your earliest reply, Jayadeep.

Hi,

To model tracer RTD, usually you define tracer(Toulene?) as a scalar instead of as a component.

I do not use fluent. The following post may be useful for you.

http://www.cfd-online.com/Forum/flue....cgi/read/6677

regards!

Jianping