Replacing TRVs, should I replace rads?

[winston1]

I suppose it's reasonable for rad makers to claim higher efficiency if it gives more kW/m2, (for given water flow and temp).

Not reasonable at all. Efficiency is nothing to do with output for a given area.

 

[fixitflav]

Not reasonable at all. Efficiency is nothing to do with output for a given area.

There's more than one way to define efficiency.

 

[winston1]

I suppose it's reasonable for rad makers to claim higher efficiency if it gives more kW/m2, (for given water flow and temp).

Not reasonable at all. Efficiency is nothing to do with output for a given area.

There's more than one way to define efficiency.

No there isn’t. Efficiency is energy in divided by energy out times 100%. Any other definition is due to ignorance.

 

[JohnD]

Maybe, but depends how you define it. It's often used in a general way when no measurement is possible. Eg "the NHS is an efficient operation".

In your example, it is not being used in a "general" way, but in a meaningless way.

 

[Lower]

Not reasonable at all. Efficiency is nothing to do with output for a given area.

No there isn’t. Efficiency is energy in divided by energy out times 100%. Any other definition is due to ignorance.

Efficiency can apply to different aspects of a design. Heat output for a given area is a standard measure of efficiency in all kinds of applications.

 

[Mottie]

Maybe the OP just meant "Will new rads chuck out more heat compared to the old ones?". Can that question be answered without splitting hairs?

 

[winston1]

Maybe the OP just meant "Will new rads chuck out more heat compared to the old ones?". Can that question be answered without splitting hairs?

It depends on the size and design. The design of central heating is such that a given output radiator is used depending on heat loss calculations for the room. Then a boiler is sized to be able to supply the required energy. If you start putting higher output radiators everywhere the boiler may not be able to cope. But at the end of the day do you need more heat? Are you cold?

 

[winston1]

Efficiency can apply to different aspects of a design. Heat output for a given area is a standard measure of efficiency in all kinds of applications.

No, that is not efficiency.

 

[Lower]

No, that is not efficiency.

How do you measure the efficiency of a heat exchanger then?

 

[winston1]

You measure the energy going into and the energy coming out of it, divide the latter by the former and multiply by 100%.

 

[Lower]

Which measure of energy out? The return energy or the energy emitted by the panel?

 

[fixitflav]

You measure the energy going into and the energy coming out of it, divide the latter by the former and multiply by 100%.

For a heat exchanger? So if there were say 5% heat loss from the external surfaces of the exchanger it would 95% efficient? That tells you nothing about its performance. You would need the kW transferred (under specified conditions), per m2 or for a specific piece of kit, depending on the details.

 

[Mottie]

It depends on the size and design. The design of central heating is such that a given output radiator is used depending on heat loss calculations for the room. Then a boiler is sized to be able to supply the required energy. If you start putting higher output radiators everywhere the boiler may not be able to cope. But at the end of the day do you need more heat? Are you cold?

Modern/new rad v the same size old crusted/slugged/painted rad. If it’s hotter, you can always turn it down.