How to obtain average Nusselt number

Caner · July 6, 2010, 00:52

Dear All

I have problem on how to obtain average nusselt number on a isothermal flat plate

I conducted numerical simulation (discretized governing equations and fed input datas are in non dimensional form) and got temperature distribution on this isothermal flat plate.According to the textbooks; Nusselt number is equal to non-dimensional temperature gradient on the surface

$\frac{\partial T^{*}}{\partial y^{*}}$ = Nu

like I said above, I got non-dimensional temperature distribution on isothermal flat plate from numerical calculation and I took temperature difference for every nodes on the plate surface and divided that difference to the non dimensional distance between wall node and first calculated domain node(which is first neighbour node to the isothermal wall node)

I have attached an image below to show you what I did to get nusselt number

http://yfrog.com/9himagepyrj

when I get every nodes nusselt number, in order to get average nusselt number distribution, I summed them all and divided to total number of nodes.

I wonder if this way correct or not?

all of your valuable comments are appreciated

Thanks in advance!

amir2920 · July 6, 2010, 06:03

Hi,

The way that you have mentioned for calculating the average Nu number is wrong.

I have written the correct formulation in an attached file.

This is my email. a_mansouri2920@yahoo.com for further information.

luiggi · July 27, 2011, 20:33

What about 3D calculationof average Nusselt number?, in this case the Nusselt number is calculated on a surface, so in my opinion should be:

$\overline{Nu}$ = $\frac{1}{Lx \times Ly}$ $\int$ $\int$ Nu(x,y) dx dy

Is that right?

Best regards,

Goutam · March 2, 2012, 15:44

Quote:

Originally Posted by amir2920

Hi,

The way that you have mentioned for calculating the average Nu number is wrong.

I have written the correct formulation in an attached file.

This is my email. a_mansouri2920@yahoo.com for further information.

Dear Amir, I have calculated Nu(x) that is local Nusselt number, Could you tell me how I will calculate the average Nusselt number in OpenFOAM?

July 6, 2010, 00:52	How to obtain average Nusselt number	#1
Caner New Member Caner Join Date: Jan 2010 Posts: 8 Rep Power: 16	Dear All I have problem on how to obtain average nusselt number on a isothermal flat plate I conducted numerical simulation (discretized governing equations and fed input datas are in non dimensional form) and got temperature distribution on this isothermal flat plate.According to the textbooks; Nusselt number is equal to non-dimensional temperature gradient on the surface $\frac{\partial T^{}}{\partial y^{}}$ = Nu like I said above, I got non-dimensional temperature distribution on isothermal flat plate from numerical calculation and I took temperature difference for every nodes on the plate surface and divided that difference to the non dimensional distance between wall node and first calculated domain node(which is first neighbour node to the isothermal wall node) I have attached an image below to show you what I did to get nusselt number http://yfrog.com/9himagepyrj when I get every nodes nusselt number, in order to get average nusselt number distribution, I summed them all and divided to total number of nodes. I wonder if this way correct or not? all of your valuable comments are appreciated Thanks in advance!

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July 27, 2011, 20:33		#3
luiggi New Member Luis Join Date: Jul 2011 Posts: 1 Rep Power: 0	What about 3D calculationof average Nusselt number?, in this case the Nusselt number is calculated on a surface, so in my opinion should be: $\overline{Nu}$ = $\frac{1}{Lx \times Ly}$ $\int$ $\int$ Nu(x,y) dx dy Is that right? Best regards,