Originally Posted by Áedán
Originally Posted by XeroHouR
you can't base how much heat your water system can take based off the heat that your rad can supposedly dissipate either I assume?
Not on its own. It's all about thermal resistance. Basically, the more heat you push into the radiator, the hotter it will get, all things being the same.
Actually yes you can. The radiator is (usually) the rate-limiting step since air is a pretty useless heat transfer material. In thermal system design one either works forwards, specifying the size of radiator needed to dissipate a given thermal load or to work in reverse, specifying the maximum acceptable load for a given radiator.
The calculations to determine the temperatures of the system at or near steady-state are pretty simple (for a chemical or mechanical engineer)