# How to calculate Nusselt Number in Fluent

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September 4, 2017, 14:05
How to calculate Nusselt Number in Fluent
#1
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Dear All

I need your help how to solve the Nuseelt number formula to plot GRAPH
between length vs Nusselt number.I do not how to calculate DTm/DX, Ts, and Tm.

Thank you
Regards
Ramakant
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 September 5, 2017, 05:45 #2 Senior Member   Cees Haringa Join Date: May 2013 Location: Delft Posts: 607 Rep Power: 13 FLUENT can give you the wall nusselt number directly; you can visualize it with contour plots or find it under reports. DO note that this is the local Nusselt number, you have to area-average it if you want a value representing a larger wall section. ramakant likes this.

September 5, 2017, 06:42
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Quote:
 Originally Posted by CeesH FLUENT can give you the wall nusselt number directly; you can visualize it with contour plots or find it under reports. DO note that this is the local Nusselt number, you have to area-average it if you want a value representing a larger wall section.

Hi..

Thank you i am trying to go this...How can i do this area-average in surface integral ?

 September 5, 2017, 08:06 #4 Senior Member   Cees Haringa Join Date: May 2013 Location: Delft Posts: 607 Rep Power: 13 reports -> surface integrals

September 5, 2017, 08:51
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Quote:
 Originally Posted by CeesH reports -> surface integrals

But it is coming not correct result.

 February 13, 2018, 03:21 hi #6 New Member   pankaj sharma Join Date: Feb 2016 Posts: 7 Rep Power: 6 hey i am working on the same stuff, but unable to figure the accurate nusselt no. please let me know if you have a solution.

March 27, 2018, 09:32
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Quote:
 Originally Posted by CeesH FLUENT can give you the wall nusselt number directly; you can visualize it with contour plots or find it under reports. DO note that this is the local Nusselt number, you have to area-average it if you want a value representing a larger wall section.
Hello Cees,

I have an array of conductive fins attached to a constant temperature hot plate losing heat to surroundings.

Here, the temperature of the fin varies along its length as it loses heat to surroundings.

I want to plot variation of Nu along the length of one fin.

Then to calculate local Nu along the length of the fin, what are the available options in Fluent. Does the "Plot-->WallFluxes--->Surface Nusselt Number" gives the right values?

Length of the base plate which is many times larger than that of the fin is taken as reference value for length.

February 26, 2019, 09:37
#8
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Oula
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Quote:
 Originally Posted by CeesH FLUENT can give you the wall nusselt number directly; you can visualize it with contour plots or find it under reports. DO note that this is the local Nusselt number, you have to area-average it if you want a value representing a larger wall section.
Hi CeesH

Can Fluent give Nu as a single value?. Another thing, I can't find "Surface Nusselt Number" in the surface integral. I did a transient simulation do you think that I need to set this parameter in advance before commencing the solution?

Your help will be greatly appreciated

February 26, 2019, 10:56
#9
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Oula
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Quote:
 Originally Posted by vidyadhar Hello Cees, I have an array of conductive fins attached to a constant temperature hot plate losing heat to surroundings. Here, the temperature of the fin varies along its length as it loses heat to surroundings. I want to plot variation of Nu along the length of one fin. Then to calculate local Nu along the length of the fin, what are the available options in Fluent. Does the "Plot-->WallFluxes--->Surface Nusselt Number" gives the right values? Length of the base plate which is many times larger than that of the fin is taken as reference value for length. Thanks in advance!

Did you manage to solve your problem? can you share your experience here?
Did you saved data of "Wall Fluxes" & "Surface Nusselt Number" first before starting the solution?

 February 26, 2019, 12:47 #10 Member   Oula Join Date: Apr 2015 Location: United Kingdom Posts: 81 Rep Power: 6 Hi again I just got this information and I would like to share it here for any future visitors To get access to the Surface Nusselt Number you need to have the following set: 1) In the Run Calculation Task Page (where you set the number of iterations), ensure you toggle on the Data Sampling for Steady State Statistics under the Options section (there is an equivalent one for Transient simulations). 2) When plotting values, you will find the variable under Unsteady Wall Statistics and then Mean Surface Nusselt Number. If Data Sampling for Time Statistics is enabled in the Run Calculation Task Page, ANSYS Fluent gathers data for time statistics while performing the simulation. The statistics that ANSYS Fluent collects at each sampling interval (which consists of the mean and the root-mean-square-error (RMSE) values) can be postprocessed by selecting Unsteady Statistics... in any of the postprocessing dialog boxes. If you select Unsteady Wall Statistics... in any of the postprocessing dialog boxes, you can view wall statistics such as Mean Pressure Coefficient, Mean Wall Shear Stress, Mean X-Wall Shear Stress, Mean Y-Wall Shear Stress, Mean Z-Wall Shear Stress, Mean Skin Friction Coefficient, Mean Surface Heat Flux, Mean Surface Heat Transfer Coef., Mean Surface Nusselt Number, Mean Surface Stanton Number. Important: When including or excluding statistics on variables, it is recommended that you re-initialize the flow statistics.

 May 8, 2019, 05:00 #11 Senior Member   vidyadhar Join Date: Jul 2016 Posts: 131 Rep Power: 5 Hi Oula, I have done like this Local heat transfer coefficients can be plotted on any surface of interest using Plot--->Wall Fluxes-->surface heat transfer coefficient. Regards, vidyadhar