On 06/05/2021 14:44, charles wrote:
In article , The Natural Philosopher
wrote:
On 06/05/2021 13:50, polygonum_on_google wrote:
On Thursday, 6 May 2021 at 13:10:20 UTC+1, Fredxx wrote:
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.
For conventional central heating radiators most heat-loss is through
convection. Air is a poor conductor.

It seems there is less overall air flow for a tall radiator than long
for a radiator with the same area and construction.

So hardly nonsense.

Likely true. But, in many cases, so what?

Let's assume a horizontal radiator is 100% efficient.

wrong understanding of 'efficient'

how about a rewrite of the OP

'vertical radiators are less *effective* at heating a room than
horizontal ones'

So, you choose a slightly larger one

I tend to use one that is 2 x overrated (80-60/in-out) over design
minimum so I can use a lower water temperature. And of course safer for
those in contact.