# Nusselt Number - Heat Transfer over a rotating cylinder

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 March 6, 2012, 20:53 Nusselt Number - Heat Transfer over a rotating cylinder #1 New Member   Leandro Join Date: Mar 2012 Posts: 8 Rep Power: 6 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 360º. Thanks you all!

 March 6, 2012, 23:13 #2 Senior Member   Erik Join Date: Feb 2011 Location: Earth (Land portion) Posts: 577 Rep Power: 11 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.

 March 7, 2012, 13:33 #3 New Member   Leandro Join Date: Mar 2012 Posts: 8 Rep Power: 6 thanks erik! But, how can I set the bulk temperature??

 March 7, 2012, 18:09 #4 Senior Member   Erik Join Date: Feb 2011 Location: Earth (Land portion) Posts: 577 Rep Power: 11 I think there is an expert parameter "tBulk for HTC" which you can set to whatever you wish. leomec88 likes this.

December 8, 2015, 14:17
nusselt expression
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mehran
Join Date: Dec 2015
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Quote:
 Originally Posted by evcelica 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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