On 16/06/2020 22:25, wrote:
On Tuesday, 16 June 2020 20:08:04 UTC+1, Fredxx wrote:
On 16/06/2020 17:59:37, tabbypurr wrote:
On Tuesday, 16 June 2020 17:51:25 UTC+1, Robin wrote:
On 16/06/2020 17:41, tabbypurr wrote:
On Tuesday, 16 June 2020 09:28:35 UTC+1, Robin wrote:
On 16/06/2020 08:55, PeterC wrote:
On Mon, 15 Jun 2020 22:30:39 +0100, Robin wrote:
On 15/06/2020 21:55, tabbypurr wrote:


A rad is 100% efficient because there is nowhere for
any waste energy to go. Thus energy input & energy
output are actually the same thing for a rad.


That's conservation of energy.

Efficiency involves the concept of usefulness - as in
the traditional definition "the ratio of the useful
work performed by a machine to the total energy
expended". On that it's entirely reasonable to
consider how a radiator in a CH system affects the
ratio of the energy released where it's wanted to the
total energy expended (i.e. including all the energy
released where it's not - e.g. in the boiler, pump, and
pipes under suspended floors).

Looking at it another way, I'd consider a radiator
which took water in at 70 degrees and passed it out at
65 degrees to be less efficient than one which passes
it out at 55 degrees. The second done is doing a much
better job at putting the energy where it's wanted.

Is that efficiency or is it effectivness?


It's a fair cop that I conflated the 2. My mitigation is
that I was trying to stop the post growing even longer.
Slightly longer 2nd attempt:

The second radiator is more effective (assuming it's a good
thing to have at least the option of warming the room
faster)

probably, though I don't know what 'second one' you refer to

and (very probably)
also more efficient

no.

in that the CH system delivers heat to the room more
efficiently.

no. You are still not grasping what radiator efficiency is.


Please state your definition.

NT: useful energy out over energy in is the definition.

With a wet radiator there are only 2 places energy can go: into
the room or out the outlet pipe. In neither case does the rad
lose any energy, hence efficiency is 100%.

Energy efficiency is always going to be 100% for a radiator.

Efficiency has several meanings. This might assist:
https://en.wikipedia.org/wiki/Effici...disambiguation)

only one of which applies here, and that is: Energy efficiency
(physics), the ratio of power consumed to useful power output


For the avoidance of difficulty in comprehending English, this may
also assist:
https://www.oxfordlearnersdictionari...lish/efficient



Adjective: doing something in a good, careful and complete way with no
waste of time, money or energy

a usage of the word that applies primarily to a person's actions.
'with no waste of energy' certainly applies to radiators. Good &
careful certainly have nothing to do with radiator efficiency.


It doesn't just have to be time, money or energy. It could be
weight or area in respect of a radiator.

sorry but no. The definition of efficiency in physics & engineering
is useful energy output divided by input. That's just what efficiency
is.

I don't buy that in this circumstance, since we have already highlighted
that in those terms its always 100% and also meaningless.

Hence one has to use the common English definition, which alludes to the
thing we do want to know, how *fast* the radiator can dissipate heat. In
other words what we are interested in is the output power, not the
proportion of energy out vs in.

A radiator may be more efficient radiating heat if the water is at
a higher temperature.

Radiation from a radiator versus convection is irrelevant to its
efficiency. That is more relevant to filament lamps.





Some further examples 2) efficient heating equipment 3) more
efficient use of energy 4) fuel-efficient cars (= that do not use
much fuel) 10) efficient in something - Modern water boilers are
highly efficient in fuel use.

those are of course the efficiency that we are discussing, useful
energy output over input.

Except we ain't...

There may be occasions where you might swap the word for
effectiveness, in many instances they are synonyms.

Perhaps English has moved on since you were at school?

It's moved on since all of us were at school, but like most words,
efficient still has the same meaning. And like so many words it also
gets used inaccurately, imprecisely and for the purposes of
promotional bs.

Good, lets all stop talking about radiator efficiency.

You can talk about overall system efficiency, or radiator power...

--
Cheers,

John.

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