radiator output calculator at differing delta T values

[old duffer]

Is there a site or can someone provide the formula to be able to calculate radiator heat output at various delta T values?

 

[Johntheo5]

Try "my" one, this is the relative output in % of a "50deg" rad which is the European standard.

Deg rad is the mean radiator temperature - the required room temp, the required room temp is typically, 20c but you can do your own calcs.
For example a rad with flow/return temps of 75C/65C and a required room temp of 20C is a 50 deg rad, ((75+65)/2) - 20. Any other deg rad output is then its (Deg Rad/50)^1.3, ie a 30 deg rad will have a output of (30/50)^1.3 X 100, 51.5% of the output of a 50 Deg Rad and so on. I'll make a table in a spreadsheet in a few minutes and display the formula

 

[old duffer]

thanks for that
I have 2 known variables and I need to find third.
so I have known room temp@ 19
Flow temp @ 40
I need to find radiator output based on those variables

 

[Johntheo5]

You can't get a relative rad output with only 2 variables, you need the rad return temp or the rad dT to give you the return temp, obviously you can only get the actual required rad output if you know the required output in kw for any particular room and then oversize your rad based on a 50Deg rad basis.

 

[old duffer]

return temp is 27

 

[Johntheo5]

You have a (40+27)/2 - 19, 14.5 deg rad with (14.5/50)^1.3, 20% output of its full rating.