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The Nusselt number is a non-dimensional parameter that provides a measure of the convection heat transfer at a surface. It is the ratio of convection to pure conduction heat transfer. We will now derive the Nussult number as a function of the given parameters and temperature.
The convection heat transfer at the pipe wall is:

We can rearrange terms to find an expression for h, the convection coefficient:

Substitute the convection coefficient expression into the Nusselt Number expression:

where
h is the convection coefficient.
k is the thermal conductivity.
L is the length scale. Similar to the Reynold's Number, the length scale is the diameter of the pipe for an internal pipe flow.
q''_w is the heat flux at the heated surface, 37.5 W/m^2.
Tw is the pipe wall temperature at a given location along the pipe.
Tm is the mean temperature in the pipe at the location where Tw is defined.

To find the temperature at the wall, click on insert >> location >> point, and name it Tw exit. Select Method to XYZ and enter 8.64, 0.06, 0 to define the coordinate of a point. Click on Expression right below Image Added and right click in the window to create a new expression named Tw. In the Definition of Tw panel, enter probe(Temperature)@Tw exit. Tw now gives the temperature at the location (8.64, 0.06, 0), which is on the exit pipe wall.
!Tw,jpg!

To export the data, click on the "export" button.  Comma Seperated Value (.csv) is able to be read by matlab and Excel, so it should be fine.

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