Hello Stressers!!!'

I know this is not a Caesar II question. But I'm doing a transient thermal analysis to calculate some thermal stresses in a pad. Basically my question is how fast (in sec.) does the temperature rises say from ambient (21 deg. C) to say 427 deg. C operating at a 24" STD wall pipe. I will use this data in the Load Curve for a Transient Thermal Analysis. What factors affect this data? Do I need to run CFD analysis to get this value (rise time of temp.) and are dependent on fluid velocity, etc.

Any expert opinion is highly appreciated. Basically, if my rise time is very fast the thermal stresses are very high obviously.

Many Thanks,