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Stove Fan Effectiveness Question


BlueStringPudding

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It's a bit of a pointless question really. A bit like asking what's the point of having a cat.

If you like having a fan on your stove then that IS the effect.

If you like having a cat (or dog) around, what is the point of that? Answer, the same. A stove fan is rather like having a pet around in your bote.

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5 minutes ago, Bargebuilder said:

Did you fail physics at school?  

I have just lifted this from the web site of a wet towel rail manufacturer as proof:

A 1500 X 600 towel rail in white gives a maximum of 2839BTU, but the chrome version is only 1945BTU

 

BSP was Tutored by the Clangers.She knows lots.

Edited by cereal tiller
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2 hours ago, Bargebuilder said:

Did you fail physics at school?  

I have just lifted this from the web site of a wet towel rail manufacturer as proof:

A 1500 X 600 towel rail in white gives a maximum of 2839BTU, but the chrome version is only 1945BTU

 

And yet the whole point of a burner is to radiate heat not retain it so the (marginally) more efficient colour scheme would be black on the inside and white or silver on the outside thereby absorbing heat from the fire and kicking it out into the boat.

The marginal difference allows aesthetics to play a role too... Just like the teapot. 

 

 

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6 hours ago, mross said:

Great paint job!  But you really ought to paint the stove and flue matt black as it would radiate a lot more heat.  The only colour worse than white would be a shiny silver.  Silver/aluminium is used on tea pots for good reason.

Mross actually got it the wrong way round.

Teapots should (ideally) retain heat so their ideal colour would be pale on the inside and dark on the outside.

Aesthetics and poshness dictate that folk make teapots in metal but they are the worst possible material for them.

Aside from the heat escaping quickly they also taint the flavour of the tea.

 

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1 hour ago, carlt said:

The marginal difference allows aesthetics to play a role too... Just like the teapot. 

The difference can be a lot more than marginal as has already been demonstrated.

 

1 hour ago, carlt said:

And yet the whole point of a burner is to radiate heat not retain it so the (marginally) more efficient colour scheme would be black on the inside and white or silver on the outside thereby absorbing heat from the fire and kicking it out into the boat.

This is quite wrong, as the worst possible colour for the outside, assuming that you want the heat to be radiated, is silver, with white being another poor choice.

 

1 hour ago, carlt said:

Teapots should (ideally) retain heat so their ideal colour would be pale on the inside and dark on the outside.

 Wrong again! The ideal external finish for a teapot if you want it to retain heat is silver.

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3 hours ago, Bargebuilder said:

The difference can be a lot more than marginal as has already been demonstrated.

 

This is quite wrong, as the worst possible colour for the outside, assuming that you want the heat to be radiated, is silver, with white being another poor choice.

 

 Wrong again! The ideal external finish for a teapot if you want it to retain heat is silver.

 

Seconded. All of that. 

Matt black both absorbs radiated heat and radiates heat out FAR more effectively than shiny silver.

Basic skoolboy fizzicks innit.  

Edited by Mike the Boilerman
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5 minutes ago, Mike the Boilerman said:

 

Seconded. All of that. 

Matt black both absorbs radiated heat and radiates heat out FAR more effectively than shiny silver.

basic skoolboy fizzicks.  

and it is even more basic skoolboy fizzicks that room heaters work through convection  more than radiation.

"Radiators" is a misnomer.

A black heater may well be radiating heat more effectively but emissivity of thermal radiation is not the main way to heat a room.

Halogen and fan heaters are true "radiators" which is why they only warm you up if you are sat directly in front of them and an Ecofan wouldn't turn if sat on top of them.

Painting your stove white or silver will not reduce it's ability to heat a room by convection by any (barely) measurable degree except by adding a very thin insulating layer.

Putting a silver or white board behind it though will heat the room immediately in front of it more effectively (which is why halogen heaters have a reflector behind the heat source).

Worrying about radiated heat is only really an issue if you want to keep heat out which is why those screens for keeping cars cool are silver on the outside.

 

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9 hours ago, Bargebuilder said:

It is a fact that matt black surfaces both absorb and radiate heat better than any other colour. The lighter and shinier the worse they are at radiating heat.

 

Write a complaint to all the stove manufacturers that use any other colour, then :closedeyes:

28 minutes ago, carlt said:

and it is even more basic skoolboy fizzicks that room heaters work through convection  more than radiation.

"Radiators" is a misnomer.

A black heater may well be radiating heat more effectively but emissivity of thermal radiation is not the main way to heat a room.

Halogen and fan heaters are true "radiators" which is why they only warm you up if you are sat directly in front of them and an Ecofan wouldn't turn if sat on top of them.

Painting your stove white or silver will not reduce it's ability to heat a room by convection by any (barely) measurable degree except by adding a very thin insulating layer.

Putting a silver or white board behind it though will heat the room immediately in front of it more effectively (which is why halogen heaters have a reflector behind the heat source).

Worrying about radiated heat is only really an issue if you want to keep heat out which is why those screens for keeping cars cool are silver on the outside.

 

:clapping:

Oh look - I have shiny white tiles behind my stove all the way up to the ceiling. :) The cumulative effect of those and my stove in whatever colour the stove is painted is probably better than the equivalent matt black painted stove without the selective surface behind. 

Edited by BlueStringPudding
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9 minutes ago, Mike the Boilerman said:

 

Frankly this is twaddle. 

You are correct and I have edited accordingly (it is early and I have been up all night) but it is nice to know that it is the only part of my post that was worth pulling apart.

Halogen heaters are, however, radiators whereas stoves and "radiators" are convectors.

Edited by carlt
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On 19/11/2017 at 07:17, carlt said:

You are correct and I have edited accordingly (it is early and I have been up all night) but it is nice to know that it is the only part of my post that was worth pulling apart.

Halogen heaters are, however, radiators whereas stoves and "radiators" are convectors.

 

I couldn't be bothered with the rest given it was mostly irrelevant, but that bit stuck out in particular.

The point is, black surfaces radiate heat more effectively than white or silver. A fact you seem unwilling to accept.

 

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1 minute ago, Mike the Boilerman said:

 

The point is, black surfaces radiate heat more effectively than white or silver. A fact you seem unwilling to accept.

 

The point is, radiated heat is largely irrelevant with a convection heater. A fact you seem unwilling to accept.

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There's another thread running at the same time as this one with 160+ posts discussing the merits of MP's Holy Grail and Ecofans. Pulling together the various views from both threads, there is a pattern emerging – for me anyway.

1). There are stove fans and stove fans. I have a 2017 Eco fan which does move air. I can feel the effect 10ft away. It looks like cheap Chinese copies do not work as well. My new one claims it moves air twice as fast as other models (265 CuFt/min). Anyone with an old/cheap fan may want to try a better one before claiming that none work.

2) We are all different. We all have different 'sensory' levels. How many of you (now we are old and grey) have lost your 'top end frequency' hearing? There is a wide difference in how we sense temperature. Look at Machpoints response in the other thread?

Machpoint005 said:

Look closely at Dr Bob's graphs above. Look at the temperature difference between the red and the green. The pictures look very dramatic, but in fact they show no more than two extremes of a temperature range of a couple of degrees. I suggest that:

  1. The temperature change would not be readily detected by a human observer who was unaware whether the fan is there or not (ie it's not a blind trial, and certainly not double-blind, which would have removed observer bias);

To me, I can feel a couple of degrees temperature differential. Machpoint obviously can't. Is this a reason why a lot of people cant feel the difference? We spent one year living in a neighbours house while we built on the next door property. It became very apparent that we noticed temp changes far more than our hosts (in a very leaky and energy inefficient house).

I wont be getting rid of my fan and will replace it when it dies. Worth every penny to me.

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Perhaps Carlt studied physics with Bluestringpudding on the planet Clanger. Clearly a case for an OFSTED inspection and special measures.

There can be no argument that both the colour and finish of a surface make a huge difference to its ability to radiate heat.

Wood stoves do rely largely on convection, but it is the radiated heat element that warms your knees from the other side of the room, it is the radiated heat that warms the fabric of the cabin, especially at low levels where the warm convected air struggles to reach and it is the radiated heat that makes the cabin feel cosy.

I have a Wallas convector heater that heats up quickly, is clean, very efficient and cheap to run, and yet I choose to lug coal a 1/4 of a mile to my boat, spend a great deal of time riddling, disposing of ash, and dusting the shelves, simply because my Squirrel stove produces a much 'nicer' heat, and that difference is down to heat radiation.

However, if you don't trust science and prefer style over performance, then you enjoy your brightly coloured stove!

Perhaps Carlt studied physics with Bluestringpudding on the planet Clanger. Clearly a case for an OFSTED inspection and special measures.

There can be no argument that both the colour and finish of a surface make a huge difference to its ability to radiate heat.

Wood stoves do rely largely on convection, but it is the radiated heat element that warms your knees from the other side of the room, it is the radiated heat that warms the fabric of the cabin, especially at low levels where the warm convected air struggles to reach and it is the radiated heat that makes the cabin feel cosy.

I have a Wallas convector heater that heats up quickly, is clean, very efficient and cheap to run, and yet I choose to lug coal a 1/4 of a mile to my boat, spend a great deal of time riddling, disposing of ash, and dusting the shelves, simply because my Squirrel stove produces a much 'nicer' heat, and that difference is down to heat radiation.

However, if you don't trust science and prefer style over performance, then you enjoy your brightly coloured stove!

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Wood stoves can be designed for convection, radiation or a mix.  The convection stoves normally have an air passage between the 'furnace' and the casing and often have visible air outlets.  Most UK stoves don't and are primarily radiating.  They will, of course, have some convection too.

But each to his own.  Your beliefs do me no harm and vice versa.

Here's another link for cynics https://www.thestoveyard.com/faqs-home/what-s-the-difference-between-a-radiant-stove-and-a-convection-stove-

and https://www.rockfordchimneysupply.com/blog-2/cat/articles-and-info/post/Wood-Stove-Convection-vs-Radiant/

If you doubt how much heat is radiating from a stove, sit in front of it with your eyes shut and get someone to hang a coat or curtain in front of you.  You will feel a difference immediately.

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17 minutes ago, bizzard said:

A Thermos flask is a wonderful thing to have. It can keep things cold as well as hot. Both lovely hot soup and a choc-ice for afters for example.

And critically and to prove the point rather well, the flask consists of two 'shells' with a vacuum  between them to eliminate convection and conduction and both internal surfaces are silvered to reduce radiation to fairly close to zero, evidenced by the fact that your coffee stays warm for many, many hours.

When they start to use blacking rather than silvering in a flask to reduce radiation, I might start thinking that Carlt has got it right after all.

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