If this website doesn't help, I can dig further:
Engineering toolbox. I think I may be able to find the one for building structures (was on a machine that crashed). I don't know if that will directly correspond. ISTR, it expressed loss or gain in temperature. From that, one could derive the needed BTU to add/gain to reach a set temp.
Isn't there a direct number to call into a chiller company, asking for needed size of one of their units for a given space? :h That may be easier and more impirical than running your own calculations.
