CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > ANSYS > CFX

Plotting of Graphs of Reynold Number Versus Length In Counter Flow Double Pipe in CFX

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   January 2, 2016, 04:55
Default Plotting of Graphs of Reynold Number Versus Length In Counter Flow Double Pipe in CFX
  #1
Senior Member
 
Shomaz ul Haq
Join Date: Aug 2015
Location: Islamabad, Pakistan
Posts: 205
Rep Power: 9
Shomaz ul Haq is on a distinguished road
Send a message via Skype™ to Shomaz ul Haq
Hi all. Hope everyone is well. I am modeling heat transfer in counter flow double pipe heat exchanger for nanofluids for the past three months. I am working without nanoparticles at the moment and just using heat exchanger with water. I have made the geometry, meshed it and ran the iterations which gave me good results. Now I am trying to plot some graphs of some variables along the length of the pipe. I am currently using constant normal speed boundary condition that is giving me constant Re number versus pipe length/axis in CFD-Post at inlet boundary condition (which I suppose it would). Now I want to use a velocity equation and not a constant normal speed boundary condition. I want to study how Re number changes and the different flow regimes (laminar, transitional, and turbulent) and boundary layer thickness and effect. I can't seem to find the relationship for velocity as a function of pipe length in counter flow double pipe heat exchanger. I have consulted numerous heat transfer articles and books. Does anybody know any relation of that kind? Would be grateful. Thanks.
Shomaz ul Haq is offline   Reply With Quote

Old   January 4, 2016, 12:16
Default
  #2
Senior Member
 
Join Date: Jun 2009
Posts: 1,437
Rep Power: 27
Opaque will become famous soon enough
Not sure what your definition of Reynolds number is, but for a uniform cross section pipe, the Re number is defined as

Re = Density * Mean Velocity * Characteristic Length (Usually Hydraulic Diameter) / Dynamic Viscosity

If your inlet boundary condition is constant in time, your mass flow is also constant in time and so is the mean velocity.

For constant property fluid, there is nothing changing on the right hand side of the definition; therefore, what are you expecting to see ?

If the inlet velocity boundary condition is a profile, not uniform in the cross section, you will see the flow developing (with a constant mean velocity for every cross section along the pipe) and you could the growth of the boundary layer until the flow is fully developed (assume the pipe is long enough). In any case, the Re number remains constant along the pipe.

Hope the above helps you.
Opaque is offline   Reply With Quote

Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Parallel User Defined Real Gas Model aeroman FLUENT 4 July 1, 2015 06:09
Fanno flow (pipe flow) in CFX Saima CFX 1 December 17, 2012 05:36
CFX Solver Reynolds Number haider760 CFX 2 March 4, 2012 22:05
REAL GAS UDF brian FLUENT 6 September 11, 2006 08:23


All times are GMT -4. The time now is 10:43.