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November 21, 2011, 03:41 
Average Nusselt Number

#1 
New Member
Kamran
Join Date: Nov 2010
Posts: 8
Rep Power: 8 
Hi everyone,
I am doing a problem in Fluent, wherein i have made a model of NACA 23012 airfoil , and placed the piccolo hole at the leading edge, after messing and running it in fluent, i need to calculate the Average Nusselt Number at the front wall of the leading edge, because thats where i need to see the heat transfer effect, in fluent, there is an option wall fluxes  surface nusselt number, but that is giving me some absurd number, can anyone tell me the formula for average nusselt number and how to add it to the custom fields.... Best Regards, Kamran 

November 21, 2011, 06:35 

#2 
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Sandeep
Join Date: Apr 2009
Location: Munich, Germany
Posts: 30
Rep Power: 9 
Hi,
In Fluent the surface nusselt number is calculated based upon the formula ((h_eff*L_ref) / k) where h_eff is heat transfer coefficient and L_ref is reference length which you define in refernce values panel and k is thermal conductivity. 

November 21, 2011, 15:07 

#3 
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Kamran
Join Date: Nov 2010
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I understand brother..this info is understood, but my question is how to calculate AVERAGE NUSSELT NUMBER ..in Fluent..do we have to define some equation based on local or suface nusselt number.


November 27, 2011, 13:01 

#4 
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Mahmood Rahi
Join Date: Jun 2009
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You create a point at the surface where you want to calculate the Nusselt number. Then use this formulae
Nu=Q*X/(TTb)K Q you cant get by using the wall fluxes , total heat transfer X is the location T is surface temperature Tb is the bulk temp, you need to create a iso surface for that where you have created the point K thermal conductivity of the Fluid 

November 29, 2011, 02:48 

#5 
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Kamran
Join Date: Nov 2010
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Thanks guys for your input...it would be of great help...keep rocking..!


February 9, 2013, 03:40 

#6 
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saman
Join Date: Jan 2013
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I wrote a code that gives average nusselt number in steady state as a scalar number for a cylinder in cross flow with Induced Vibrations
local nusselt nuL= (Wall Heat Flux *shoa*2[m])/(75 [K]*Thermal Conductivity ) that 75 is Temperature difference average nusselt number nuave=areaAve(nuL)@Pipe1 but I need a way that plot average nusselt number as a function of time like the follow picture of course I Send the variable nuave to a monitor point, but it gives this error in follow picture. please help me 

August 20, 2014, 06:46 
NuTime History plot

#7 
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Chunnu
Join Date: Aug 2014
Posts: 1
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hello fiends,
i m calculate average nusselt no. flow over a cylinder. i just try to plot a graph between nusselt no. and time, like dragtime history. Plz any one can give me idea to plot graph. 

August 20, 2014, 18:58 

#8 
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f_alafoo
Join Date: Jun 2013
Location: Bahrain
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Dear Kamran,
As I understand in your problem, the values you are getting in the Fluent at the leading edge of the airfoil is the local Nusselt number, one thing you can do is to take the average over a specific region as you are looking for. 

April 2, 2016, 08:41 

#9 
New Member
Join Date: Mar 2013
Posts: 10
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This method is valid for a flow over a flat plane or for a internal flow in a channel?
Thank you. 

Tags 
fluent 6.3.26, nusselt number, post processing 
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