Cool down time calculation 1

[narenr]

I have written a code for calculating temperature profile along the coated pipeline length. Now I need to calculate cool-down time. Can somebody suggest the equations.
Thanks.


Narendranath R
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[MortenA]

You could assume that the liquid inside the pipe maintains a uniform temperature at a give cross section (this simplifies everything a lot. Then use the same heat transfer equations that you used the first time but instead of assuming a steady state profile - use this profile to calculate a time step wise cooling for each of your intial length segments. If you just want to find the max or min temp then use the first or last segment only.

The inside film coefficient would be something like the formular used for a outside convection. try to look in Perry or a heat transfer text book. There must be a formular for this special case (or at leat the exponents for use in the Nu=a*Pr^b*Re^c type of formular).

Best reagards

Morten