Average Nusselt Number

kamran651 · November 21, 2011, 03:41

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

sandeep_tu · November 21, 2011, 06:35

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.

kamran651 · November 21, 2011, 15:07

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.

rahimahm · November 27, 2011, 13:01

You create a point at the surface where you want to calculate the Nusselt number. Then use this formulae
Nu=Q*X/(T-Tb)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

kamran651 · November 29, 2011, 02:48

Thanks guys for your input...it would be of great help...keep rocking..!

samanpnh · February 9, 2013, 03:40

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

cldewangan · August 20, 2014, 07:46

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 drag-time history. Plz any one can give me idea to plot graph.

fadhel · August 20, 2014, 19:58

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.

faycal2013 · April 2, 2016, 09:41

This method is valid for a flow over a flat plane or for a internal flow in a channel?
Thank you.

November 21, 2011, 03:41	Average Nusselt Number	#1
kamran651 New Member Kamran Join Date: Nov 2010 Posts: 8 Rep Power: 16	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

August 20, 2014, 07:46	Nu-Time History plot	#7
cldewangan New Member Chunnu Join Date: Aug 2014 Posts: 1 Rep Power: 0	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 drag-time history. Plz any one can give me idea to plot graph.

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November 21, 2011, 06:35		#2
sandeep_tu Member Sandeep Join Date: Apr 2009 Location: Munich, Germany Posts: 30 Rep Power: 17	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
kamran651 New Member Kamran Join Date: Nov 2010 Posts: 8 Rep Power: 16	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
rahimahm New Member Mahmood Rahi Join Date: Jun 2009 Posts: 1 Rep Power: 0	You create a point at the surface where you want to calculate the Nusselt number. Then use this formulae Nu=Q*X/(T-Tb)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
kamran651 New Member Kamran Join Date: Nov 2010 Posts: 8 Rep Power: 16	Thanks guys for your input...it would be of great help...keep rocking..!

August 20, 2014, 19:58		#8
fadhel New Member f_alafoo Join Date: Jun 2013 Location: Bahrain Posts: 2 Rep Power: 0	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, 09:41		#9
faycal2013 New Member Join Date: Mar 2013 Posts: 10 Rep Power: 13	This method is valid for a flow over a flat plane or for a internal flow in a channel? Thank you.