How can I find where the code for those limits is located?
I want to do this because I want larger fireballs to move faster upwards like the smaller ones do and maybe increasing this value would help (I don’t want to change the simulation speed or add any fake velocity to it.):
Make sure you have developer tooltips turned on (Edit / Preferences / Interface / “User Tooltips” and “Python Tooltips”). Hover over that input and note that the python name includes “flow_settings.temperature”. So you could grep the source for “flow_settings” or “temperature”. But I would instead grep the text of the tooltip hint: “Temperature difference to ambient temperature”. That will take you to the definition of the property and you’ll see the limits set.
If your testing determines that there is utility in changing those limits, then submit a patch. Just make sure to sell the idea in detail in the patch details, even including videos is appreciated.