[Incoherent]

There might be a rather simple way to get a C/W number for a radiator.
The maths behind it is rather complex but try this.
You need to know:
1. Water temp
2. Water volume in litres
3. Water heat capacity in j/l°C

Run system with no load except the pump itself and the fan running and run until the water temperature has stabilised. Record temperature.
Switch on load and log temperature and time. Run system until the temperature has stabilised. I mean really stabilised.
Find the time t (in seconds) at which the temperature was half way towards the final loaded temperature.
t/(natural log of 2) = tau
tau/(Cp*volume)= C/W of radiator

This is the UI for some rather complex maths, which is possibly (or even probably) wrong but I think it works. Half lives, timeconstants, charging phenomena which I have attempted to hack away at.
I believe it works without knowing the watts or air temperature, they are intrinsically bound to tau. Also it does not matter what your starting point vs end temperature is.


T=(1-e^(-t/R.Cp.v))*(R.Cp.v.(Q/v.Cp)+Tamb-Tinit)+Tinit

T=(1-e^(-t/tau))*(Tend-Tinit)+Tinit