"Fredxx" wrote in message
...
On 06/05/2021 18:29, Rod Speed wrote:
Fredxx wrote
Rod Speed wrote
Robin wrote
jon wrote

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

As I think I said the last time this came up, my physics is nowhere
near good enough to decide "by inspection" whether a vertical or
horizontal radiator is better at transferring heat to a room.

Yes, you clearly have that problem. Plenty of us dont.

I don't know why you say that,

Because its true ? Novel concept I realise.

as the chimney effect can sometimes be very good at providing a good
airflow.

They both have that. The difference is that the
horizontal radiators have the air moving over
much less of the radiator so the radiator has
more cold air moving over it and so you will
see more heat moving out of the radiator
into the airstream.

So at first sight it's not obvious which orientation is best.

Only for those who dont have a clue about the basics.

Only those with hindsight will think differently.

Wrong.

And (like some others)

Who have the same problem.

I saw too many /known/ unknowns - e.g laminar flow? temperature of air
exiting top? chimney effect? - quite apart from the possible unknown^2

None of that matters. What matters is the vertical distance.

There is no chimney effect with a radiator.

The gap between the radiator and the wall and radiator height will
determine air speed over the radiator.

But that isnt different with the two types of radiator.

What matter is the distance that the cold air at the bottom of
the radiator moves over before it gets to the top of the radiator.

If you think differently, please feel free to cite an explanation why
this isn't the case.

Just did. And dont need a cite, just an explanation.

You haven't explained why a larger temperature difference within an
enclosed space such as a flue or the space around a radiator won't create
a bigger draught when we know the opposite is generally true.

This paper for instance:
http://cit.edu.ly/wp-content/uploads/2018/02/15-091.pdf

University of Zawia, hardly one of the world's great universitys.
And they only use aspect ratios up to 2 and no verticals, so
none of that paper is relevant anyway.

suggests the optimum aspect ratio of the radiator is highly dependent on
wall height.

Ah yes:

https://groups.google.com/g/uk.d-i-y...m/lwVTe0U-U3YJ