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-   -   Average Nusselt Number (https://www.cfd-online.com/Forums/fluent/94606-average-nusselt-number.html)

 kamran651 November 21, 2011 03:41

Average Nusselt Number

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) http://www.cfd-online.com/Forums/dat.../jIQP3/GUXAQA7 http://www.cfd-online.com/Forums/dat.../jIQP3/GUXAQA7 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

2 Attachment(s)
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

 cldewangan August 20, 2014 06:46

Nu-Time History plot

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.