On Tuesday, 16 June 2020 22:49:26 UTC+1, Fredxx wrote:

You're very much on your own when it comes to your definition of
radiator efficiency. This should help give you an indication of your
losing argument:
https://lmgtfy.com/?q=efficiency+of+a+radiator&s=l

The application of efficiency to a radiator isn't just heat out / heat
in. Best get used to it or be forever stuck in the past and viewed as
senile.

come back when you've got a fact to offer us.