Rads???

Looking for a new rad for the lounge at Handyman Towers.

Wickes list a 60mm high x 700mm wide @ 4370btu/1280w and a 700mm high x

60mm wide @ 3952btu/1158w

Since they are exactly the same surface area, why is one 10% more efficient than the other?

Reply to
The Medway Handyman
Loading thread data ...

Convection?

AB

Reply to
Archibald

Do they have the same surface area though? The fins between the two panels cover nearly the whole width, but stop well short of the full height. I guess that means the two shapes have differing fin surface areas. I can't be bothered to do the maths though.

Then there's the trade-off between many short fins and few tall ones...

Cheers,

Colin.

Reply to
Colin Stamp

But are they "exactly the same surface area"?

Is the pattern of waterways and between waterways identical?

Are the waterways the same diameter, shape length and volume?

Are they the same thickness?

If they have fins are the fins exactly the same size and number?

Is the spacing of the fins the same?

Anything else different that could effect the efficiency?

Reply to
Old Codger

Even if they did they wouldn't match. As the air rises next to the rad it gets hotter and the heat transfer gets less as the temp difference is less. So the extra 100 mm on the height will transfer less heat than the extra

100 mm on the width.
Reply to
dennis

Height is more efficient than width, due to chimney effect.

Reply to
Andrew Gabriel

It's not any more efficient; it has a higher output.

It is possible that different specs are given for different water flow and return temperatures.

Mrs Handyman will probably prefer (a) the more expensive or (b) the one you didn't buy.

Owain

Reply to
spuorgelgoog

Except that the higher narrower one claims to give out *less* heat!

[I'm assuming that the smaller dimension is 600 in each case, and not 60!]
Reply to
Roger Mills

I'm sure Mrs Handyman prefers the one that matches the wallpaper/curtains/sofa/this weeks' choice of paper napkins

tim

Reply to
tim......

How many fin things do they have?

There's a number coding something like

11 - having one panel and one fin 12 one panel and 2 fins 21 having two panels and one fin 22 two panels and 2 fins.

They might not be called fins.. but you know the things I mean.

Reply to
mogga

Never seen one of those!

Four of mine have 3 panels 3 fins.

Reply to
Andrew Gabriel

However the fins are arranged, the unit that stands taller will not radiate heat as efficiently. By the time the convection current carries the air from bottom to the top of the radiator, it will hotter than that of the wider, lower unit. So assuming that the surface area including fins is the same, then the heat tranfer would be limited by the reduced temperature gradient as the increasingly warmer air ascends.

AB

Reply to
Archibald

I'm not sure it's so simple. I can't do the sums but as others have pointed out there is eg the way that the velocity of air flow increases with the height of the radiator. (Hence eg one book states "a long, low radiator will therefore give lower convective output than a short tall radiator of the same area"[1]). I'm inclined then to think that the radiator manufacturers' figures are realisitic - not least as there'd be open to prosecution if they are demonstrably wrong.

[1]Heat and Mass Transfer in Buildings (Hardback) By (author) Keith Moss
Reply to
Robin

Neither have I! Unless always covered, there'd be fins sticking out at the front - bit sharp for domestic use.

Reply to
PeterC

I only said it was something like... Couldn't find the document I'd read it on the other week...

That's a 12 but apparently not as I remembered...

formatting link

Reply to
mogga

The photo shows that it is 'covered'; the diagram looks like half a 22 and half a 21.

Reply to
PeterC

While we're on radiators ... most rads you see nowadays are plumbed BBOE, is there any reason not to plumb them TBSE? Providing support to the tall vertical pipe I can see being one possible issue.

Reply to
Andy Burns

The important thing is that the outlet is at the bottom. On a gravity system, the inlet must be at the top. On a pumped system, inlet can be top or bottom. When inlet is connected to the bottom, if you look at the radiator with an IR camera, you can see the hot water all rises directly to the top in the first channel, and piping it to the top instead makes no difference.

Reply to
Andrew Gabriel

HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.