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-   -   Nusselt Number - Heat Transfer over a rotating cylinder (http://www.cfd-online.com/Forums/cfx/98259-nusselt-number-heat-transfer-over-rotating-cylinder.html)

leomec88 March 6, 2012 20:53

Nusselt Number - Heat Transfer over a rotating cylinder
 
Hello guys,
I'm making a CFX simulating that consists on a air flow over a heated rotating cylinder. I would like to know how to obtain the Nusselt Number and also the averagen Nu for this situation over the cylinder. I know I have the wall heat transfer transfer coefficient but I also need to know how to creat a expression for Nu and how to create a graphic for those values of Nu. I want to keep my x axis from 0 to 2 π or 0 to 360. Thanks you all!

evcelica March 6, 2012 23:13

You can do this by "create new expression" and insert your formula for Nusselt. remember if you use the wall heat tranfer coefficient it will default to using the adjacent temperature not your bulk temperature.

After you have made this expression you can also create another expression for the average Nusselt: areaAve(Nusselt)@cylinder.

To create a graphic, you define a new variable that references your Nusselt expression, and you can use this variable in a contour.

leomec88 March 7, 2012 13:33

thanks erik! But, how can I set the bulk temperature??

evcelica March 7, 2012 18:09

I think there is an expert parameter "tBulk for HTC" which you can set to whatever you wish.

mehyan December 8, 2015 14:17

nusselt expression
 
Quote:

Originally Posted by evcelica (Post 348020)
You can do this by "create new expression" and insert your formula for Nusselt. remember if you use the wall heat tranfer coefficient it will default to using the adjacent temperature not your bulk temperature.

After you have made this expression you can also create another expression for the average Nusselt: areaAve(Nusselt)@cylinder.

To create a graphic, you define a new variable that references your Nusselt expression, and you can use this variable in a contour.

what is the expression of nusselt number for double pipe heat exchanger?


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