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Temperature at outlet for non-isothermal laminar flow in circular tube

Posted 27 avr. 2015, 07:20 UTC−4 Fluid & Heat, Heat Transfer & Phase Change, Computational Fluid Dynamics (CFD), Results & Visualization Version 5.1 4 Replies

Fanny Lindberg
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I am examining a non-isothermal laminar flow in circular tube in COMSOL where the heat transfer fluid in the tube is heated as is passes the tube. Since the flow is laminar a velocity profile will form. This will impact the outlet temperature since the average temperature at the outlet won't be the actual outlet temperature, i.e. the heat transfer fluid in the middle will have twice the velocity of the average and hence the fluid with this temperature will exit in a greater extent.

How can I take the velocity profile and circular cross-section into account and get the "actual" outlet temperature?

Thank you!
4 Replies Last Post 3 mai 2015, 14:48 UTC−4
Frank van Gool COMSOL Employee

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Posted: 10 years ago 28 avr. 2015, 11:09 UTC−4
Dear Fanny,

you can take the integral of the velocity times the temperature (w*T). Where you use the checkbox "compute surface integral".
This value should then be divided by the integal of the velocity only (total flux).

Best regards,
Frank
Dear Fanny, you can take the integral of the velocity times the temperature (w*T). Where you use the checkbox "compute surface integral". This value should then be divided by the integal of the velocity only (total flux). Best regards, Frank
Daniel Connelly
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Posted: 10 years ago 28 avr. 2015, 11:19 UTC−4
Shouldn't this be additionally weighted by the local mass density?
Shouldn't this be additionally weighted by the local mass density?
Fanny Lindberg
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Posted: 10 years ago 3 mai 2015, 14:47 UTC−4
Thank you! Though, I do not quite understand what you mean by "total flux" do you refer to the normal inlet velocity or something else?
Thank you! Though, I do not quite understand what you mean by "total flux" do you refer to the normal inlet velocity or something else?
Fanny Lindberg
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Posted: 10 years ago 3 mai 2015, 14:48 UTC−4

Shouldn't this be additionally weighted by the local mass density?


Yup, though the density does not vary too much so I will disregard this.
[QUOTE] Shouldn't this be additionally weighted by the local mass density? [/QUOTE] Yup, though the density does not vary too much so I will disregard this.

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