On 06/05/2021 12:55, jon wrote:

What is this nonsense, heat is dissipated by radiation, convection or
conduction so how come efficiency becomes a problem.

Very easily. How 'efficient' is a radiator in a polystyrene box?

What the OP means is not heat in to heat out, but peak heat flow.

a vertical radiator will be transferring heat from its top to already
hot air, so less 'efficient' in terms of peak heatflow into the room, in
the same way that I have 2KW heaters the size of a cornflake packet
because they are fan blown

With 'radiators' airflow is everything. There is not much 'radiation'
going on at 60C...


--
There is something fascinating about science. One gets such wholesale
returns of conjecture out of such a trifling investment of fact.

Mark Twain