# HTC in Pipe flow

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 June 9, 2011, 06:59 #2 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,728 Rep Power: 143 You cannot simply use the mesh recommendations from the literature. Half the time they do not check properly, half the time they use a different solver with different requirements. This FAQ has some general tips. http://www.cfd-online.com/Wiki/Ansys..._inaccurate.3F But heat transfer modelling is far from accurate. Errors of 50% can happen. A big source of errors is the turbulence model, getting the heat transfer right is usually even harder than getting the bulk flow right. Also, the point of a turbulence model is that a 3D transient flow can be reduced to a 2D steady flow. The turbulence model does the simplification by modelling the effects of the turbulent fluctuations on the bulk flow.

 June 9, 2011, 08:50 #3 New Member   Join Date: Jun 2011 Posts: 24 Rep Power: 14 Thanks for your answer. Actually I don't think it's the mesh. I modified/refined it four times and always got exactly the same results. On my way to desperation i already conducted a transient simulation run and *tataaa* got the same 27000 W/Mē. What could be wrong, do you have any hints?

 June 9, 2011, 18:28 #4 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,728 Rep Power: 143 The FAQ discusses much more than just the mesh.

 May 6, 2013, 14:00 #5 New Member   Soham Harshe Join Date: May 2013 Posts: 2 Rep Power: 0 Hello I am new to star ccm+ and I am trying to simulate laminar flow of mercury through the pipe of diameter 1cm and flow avg velocity = 0.022m/s. Re=2000 and constant heat flux of 25000W/m^2 through the walls. the pipe length is 2m. flow inlet temperature 300K what should I keep static temp of outlet ? What boundary conditions shall I set to get appropriate solution ? (Currently I am not at all getting proper results) Please Help...

 May 6, 2013, 18:53 #6 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,728 Rep Power: 143 Try the star CCM forum: http://www.cfd-online.com/Forums/star-ccm/

 May 6, 2013, 22:00 #7 Senior Member   Erik Join Date: Feb 2011 Location: Earth (Land portion) Posts: 1,171 Rep Power: 23 I have simulated single phase tube heat transfer with CFX before and was within about half a percent from the Petukhov correlation. I used SST and had a Y+ of about 1. So it worked very well for me. I see you say you have an annular pipe (tube in a tube), what correlation did Gnielinski give for a turbulent annulus? You describe only 1 diameter? Are you looking at Hybrid values for wall temperature? What did you pick for "bulk temperature" It should be a function of length along your pipe which you would calculate with a simple mass and energy balance. I could be wrong, but I'm guessing there may be something wrong with the way you are calculating the HTC.