Eco Fan

[IanD]

9 minutes ago, Jim Riley said:

But they still work, for 20 beer tokens it's a no brainer. A simple heat sink would keep the heat in the vicinity of the stove,, assisted by convection, whereas there is a greater airflow with the fan. 

The big argument is whether the airflow is actually big enough to make a difference -- some people have said it is, some have said it has little or no effect. For sure those fans are pretty feeble compared to anything else used to push air around a room even if they look like they're spinning fast, so maybe the improvement is mostly down to the placebo effect -- people think it's working so they feel warmer/cooler...

7 minutes ago, Mike Todd said:

I was about to ask the same! Where does the absorbed heat energy go if not into electricity or radiated heat? 

99% of it is heat, and warms the air up -- but there's no extra heat generated, it all comes from the stove, the stove just runs a little bit cooler.

 

1% (maybe) gets turned into electricity to drive the fan. A DC fan with only a few watts (at best!) driving it doesn't move much air, and I suspect that most of them have well under a watt to play with...

Edited December 7, 2021 by IanD

[Jim Riley]

7 minutes ago, IanD said:

The big argument is whether the airflow is actually big enough to make a difference -- some people have said it is, some have said it has little or no effect. For sure those fans are pretty feeble compared to anything else used to push air around a room even if they look like they're spinning fast, so maybe the improvement is mostly down to the placebo effect -- people think it's working so they feel warmer/cooler...

99% of it is heat, and warms the air up -- but there's no extra heat generated, it all comes from the stove, the stove just runs a little bit cooler.

 

1% (maybe) gets turned into electricity to drive the fan. A DC fan with only a few watts (at best!) driving it doesn't move much air, and I suspect that most of them have well under a watt to play with...

Slow and steady does it, take ncertainly notice a difference at home, a more even heat spread around the house, if doors are left open. 

 

 

[IanD]

1 minute ago, Jim Riley said:

Slow and steady does it, take ncertainly notice a difference at home, a more even heat spread around the house, if doors are left open. 

 

Lots of cases of people thinking something makes a difference which turn out to not to be the case when actually tested, and especially if they don't know which case they're seeing -- exotic cables, green markers on CDs, gold-plated HDMI cables...

 

You might be right or you might not; other people have said that they make a big difference or none. Proper testing is the only way to answer the question... 😉

[Jen-in-Wellies]

The heat going up the ecofan from the stove top plate is mostly radiated and convected from the stem below the thermoelectric generator and from the heatsink fins above. The thermoelectric generator itself is horribly inefficient at turning heat flow across the module in to electricity. That small amount of power generated is what turns the fan and allegedly moves the air.

[Mike Todd]

15 hours ago, Jen-in-Wellies said:

The heat going up the ecofan from the stove top plate is mostly radiated and convected from the stem below the thermoelectric generator and from the heatsink fins above. The thermoelectric generator itself is horribly inefficient at turning heat flow across the module in to electricity. That small amount of power generated is what turns the fan and allegedly moves the air.

Only inefficient in the sense that a hydro scheme only extracts a proportion of the kinetic/potential energy in the water flow - much of it bypasses the system.

[IanD]

1 hour ago, Mike Todd said:

Only inefficient in the sense that a hydro scheme only extracts a proportion of the kinetic/potential energy in the water flow - much of it bypasses the system.

True, but unless the fan actually moves enough air to make a difference you'd get the same effect putting any cheap finned radiator on top of the stove -- and in practice though this drops the stovetop temperature a bit (which is why the kettle won't boil) it doesn't actually generate any more heat from the fuel, what happens is you get a bit more heat into the room from convection and a bit less from radiation but the total heating power is unchanged.

 

So the key question remains -- do ecofans actually move enough air to make a noticeable difference in the temperature distribution in the room? Given the low fan power I suspect not, the only way to prove it (unless somebody has access to some heavy-duty CFD thermal simulation software like Flotherm or Comsol, which costs thousands of pounds a year) is to do some properly controlled measurements of room temperature and temperature gradients.

 

For this you would really need a stove with constant output power so a solid fuel one won't really do (so diesel?), plus a constant outside temperature and enough time (several hours?) to let the room temperature and airflow to stabilise.

 

I'm not being a nit-picking theorist here, this is what you need to do in any test to get results that are actually valid, as opposed to marketing claims or "I know it works because it does" statements that turn out to be wrong when eventually tested.

 

This wouldn't be that difficult to do given the right equipment and some time, but AFAIK nobody has actually done it -- and until then, all the claims are just that, they may be true or just as valid as Trump's "stolen election" claims.

 

Maybe this has been done, though I doubt it because all the ecofan manufacturers and supporters would be shouting it from the rooftops if it proved the fans did what they claim. My suspicion is that either it hasn't been done (because the manufacturers know their claims are dodgy so don't want this to come to light), or even worse that they have been done and showed that the fans were ineffective but the results were then buried. Ooh, a new conspiracy theory raises its ugly head... 😉

 

Anyone know of any proper measurements to prove this one way or the other? Not just anecdotal evidence (e.g. "it definitely makes a difference" or "it moves a lot of air") but real results (e.g. "difference in temperature between the two ends of the room was reduced from 10C to 5C")

[ditchcrawler]

7 minutes ago, IanD said:

True, but unless the fan actually moves enough air to make a difference you'd get the same effect putting any cheap finned radiator on top of the stove -- and in practice though this drops the stovetop temperature a bit (which is why the kettle won't boil) it doesn't actually generate any more heat from the fuel, what happens is you get a bit more heat into the room from convection and a bit less from radiation but the total heating power is unchanged. 

Did anyone suggest it did generate more heat. A smouldering taper will indicate the air movement

[Tony Brooks]

Dr Bob did those measurements and posted them on this forum with diagrams, but I can't find the thread. It did show a degree of better heat distribution.

[IanD]

1 minute ago, Tony Brooks said:

Dr Bob did those measurements and posted them on this forum with diagrams, but I can't find the thread. It did show a degree of better heat distribution.

If the measurements were done properly -- so maybe not from the point of view of an ecofan enthusiast trying to prove they're correct -- I'm sure many people would love to see them...

[Tony Brooks]

1 minute ago, IanD said:

If the measurements were done properly -- so maybe not from the point of view of an ecofan enthusiast trying to prove they're correct -- I'm sure many people would love to see them...

 

It seems Dr Bob is some kind of scientist so one would hope his methods would be more reliable than most. How he condurted the tests are all in the topic, but as I said, I can't find it to link to. It must be buried in a long topic.

[IanD]

5 minutes ago, Tony Brooks said:

 

It seems Dr Bob is some kind of scientist so one would hope his methods would be more reliable than most. How he condurted the tests are all in the topic, but as I said, I can't find it to link to. It must be buried in a long topic.

Plenty of scientists believe that $1000 silver mains cables make their hi-fi sound better to their golden ears.

 

Many scientists know an enormous amount about their own specialist field, but no more about other fields than Joe Public. At least they should understand the scientific method and how to run trials, but this can sometimes be trumped (see what I did there?) by beliefs which are wrong -- see silver mains cables... 😉

 

If Dr. Bob did proper controlled tests, kudos to him -- let's see them 🙂

Edited December 8, 2021 by IanD

[Jim Riley]

When I first put a woodstove in at home there were colder areas in the room, a noticeable heat gradient. Once I put a fan on top the temperature around the room evened up, no noticeable gradient. With the fan going and doors left open the adjacent rooms get warmer.

A ribbon held in front of the fan will go horizontal in the air flow. It may not be a huge air flow, but over the day it shifts the air around. 

While not being able to quote actual temperatures, just as I know if I put my hand in a pan of bubbling water on the stove, or touch a piece of red hot metal, I will get burnt, it is possible to assess relative heat without instruments. 

[GUMPY]

We have the same, with no fan there is a definite cold layer of air beneath the hot layer. With the fan there are no noticeable layers.

Works for me 😱

[IanD]

1 minute ago, Jim Riley said:

When I first put a woodstove in at home there were colder areas in the room, a noticeable heat gradient. Once I put a fan on top the temperature around the room evened up, no noticeable gradient. With the fan going and doors left open the adjacent rooms get warmer.

A ribbon held in front of the fan will go horizontal in the air flow. It may not be a huge air flow, but over the day it shifts the air around. 

While not being able to quote actual temperatures, just as I know if I put my hand in a pan of bubbling water on the stove, or touch a piece of red hot metal, I will get burnt, it is possible to assess relative heat without instruments. 

It is indeed, but nobody is debating that if you hold a ribbon in front of the fan it will get blown sideways, the question is -- does it make a big enough difference to the heat distribution across a room?

 

Subjective "it gets warmer" results are not reliable -- do you know about "confirmation bias"?

 

Loads and *loads* of cases of this in many fields, basically people believe what they want/expect to see -- and to be clear they're not lying, they genuinely do believe what they say. But they're quite often wrong, which is why scientists do actual tests to either confirm they're right or show that they're not... 😉

[IanD]

1 minute ago, Loddon said:

We have the same, with no fan there is a definite cold layer of air beneath the hot layer. With the fan there are no noticeable layers.

Works for me 😱

And other people have said "It tried one and it made no difference at all". And then "I swapped it for a "better" one and that didn't do anything either".

 

Who is right? Both of you? Neither of you? One of you? (which one?) Does it depend on which fan you use, or which stove you use it on? Do they always work, never work, or somewhere in between?

 

There are lots of classic experiments in all sorts of areas showing that you absolutely can't rely on people's opinions when they know the expected outcome -- including "this is warmer", and the placebo effect -- and the nocebo effect, when even if they're *told* it's a placebo they still report feeling better. The mind can easily be convinced of many things, some of them not true.

 

So you might be right. Or you might just *believe* that you're right when you're not. Which might make you happy, but not right 😉

[tree monkey]

42 minutes ago, IanD said:

Plenty of scientists believe that $1000 silver mains cables make their hi-fi sound better to their golden ears.

 

Many scientists know an enormous amount about their own specialist field, but no more about other fields than Joe Public. At least they should understand the scientific method and how to run trials, but this can sometimes be trumped (see what I did there?) by beliefs which are wrong -- see silver mains cables... 😉

 

If Dr. Bob did proper controlled tests, kudos to him -- let's see them 🙂

My memory tells me you were part of that thread where Bob found some Canadian data and did some tests of his own

[IanD]

6 minutes ago, tree monkey said:

My memory tells me you were part of that thread where Bob found some Canadian data and did some tests of his own

I have vague memories, but I can't find it either. IIRC there was some debate at the time about the measurements but I could well be wrong, it was some time ago...

 

(and I'm afraid Dr.Bob dented any claim to scientific credibility -- in my mind, at least -- by his biased and inaccurate posts about composting toilets, not that I want to start that discussion up again)

 

As I said, if he does have some valid results, maybe it would be worth posting them again since they seem to be lost in the mists of CWDF time...

Edited December 8, 2021 by IanD

[Jim Riley]

12 minutes ago, IanD said:

And other people have said "It tried one and it made no difference at all". And then "I swapped it for a "better" one and that didn't do anything either".

 

Who is right? Both of you? Neither of you? One of you? (which one?) Does it depend on which fan you use, or which stove you use it on? Do they always work, never work, or somewhere in between?

 

There are lots of classic experiments in all sorts of areas showing that you absolutely can't rely on people's opinions when they know the expected outcome -- including "this is warmer", and the placebo effect -- and the nocebo effect, when even if they're *told* it's a placebo they still report feeling better. The mind can easily be convinced of many things, some of them not true.

 

So you might be right. Or you might just *believe* that you're right when you're not. Which might make you happy, but not right 😉

I think there's a relationship between the unbelievers and voting brexit, eg @mrsmelly for one.

[tree monkey]

7 minutes ago, Jim Riley said:

I think there's a relationship between the unbelievers and voting brexit, eg @mrsmelly for one.

Oy

 

[BlueStringPudding]

1 hour ago, ditchcrawler said:

Did anyone suggest it did generate more heat. A smouldering taper will indicate the air movement

As does the smoke from incense or fine particles of ash. 

The former I did as a test a few winters ago. (No discernible change in the movement of the smoke) 

The latter I do every day in the winter, because I place a pot on the stove top into which I empty the ash pan, before taking the pot outside to cool. The pot is positioned right in front of the stove top fan, with the fan "blowing" across the top of the pot from left to right. So the finer ash particles in the air ought to move to the right, or at least curl or circulate round. Here's the daily official Pud eco fan test results:

 

With the fan turning, the fine particles of ash (hot or cold) that puff up into the air from tipping out the ash pan into the pot, float vertically upwards following the rising heat from the stove top and flue, with a small amount of the ash particles moving up and left towards the closed but presumably draughty window nearby. 

 

With no stove top fan, the fine particles of ash that puff up into the air from tipping out the ash pan into the pot, float vertically upwards following the rising heat from the stove top and flue, with a small amount of the ash particles moving up and left towards the closed but presumably draughty window nearby. 

 

In other words, the fan makes no visible difference at all to the air flow, using either smoke to test it or fine ash particles. 

 

These are the results of the BlueStringPudding jury. 😊

 

So if you don't already have an eco fan, I would suggest you don't waste your money on buying one. If you do have one, enjoy its pretty spinning propellers and the sense of comfort that you feel warmer at the other end of your boat, whether it's real or imagined. 😊

Edited December 8, 2021 by BlueStringPudding

[Higgs]

Not sure how much work the eco fan is doing to circulate warm air. It is definitely moving air enough to notice it has a fan effect. I'd rate it as not much more than a curiosity. Once purchased and in use, it is converting one source of energy into another, and interesting for that. 

 

 

[Alway Swilby]

I don't particularly care about any scientific tests to prove whether a stove top fan works or not. IanD can go on about it all he likes about placebos etc. but I know that without a fan on the fire my feet get cold when I'm sitting on the sofa. With a £20 fan on the fire my feet don't get cold. Worth it in my book even if they're proven by science not to work.

Edited December 8, 2021 by Alway Swilby

[Higgs]

I've just blown some smoke into the fan, and detected it moving over 8' away. 

 

 

[IanD]

21 minutes ago, Alway Swilby said:

I don't particularly care about any scientific tests to prove whether a stove top fan works or not. IanD can go on about it all he likes about placebos etc. but I know that without a fan on the fire my feet get cold when I'm sitting on the sofa. With a £20 fan on the fire my feet don't get cold. Worth it in my book even if they're proven by science not to work.

Nobody has proved it to not work -- or work -- by science, unless some actual test results -- objective (measured) not subjective (feeling) are provided.

 

You believe (opinion) that your feet are warmer because the ecofan is on. You don't know (fact) that they're warmer, because the brain plays tricks on us -- when we expect something to happen we often think it happens, even if it doesn't.

 

There are literally thousands of cases of this happening in any field you can name, it's why (reliable) tests are needed instead of relying on (unreliable) opinions. Confirmation bias means that people aren't lying, they genuinely believe that what they hear/feel is real, even if it's not. Or it could be real, even if they believe it isn't.

 

None of which means that you're wrong, it's possible that the fan is doing what you think it is -- but your opinion doesn't prove it... 😉

Edited December 8, 2021 by IanD

[Alway Swilby]

4 minutes ago, IanD said:

Nobody has proved it to not work -- or work -- by science, unless some actual test results -- objective (measured) not subjective (feeling) are provided.

 

You believe (opinion) that your feet are warmer because the ecofan is on. You don't know (fact) that they're warmer, because the brain plays tricks on us -- when we expect something to happen we often think it happens, even if it doesn't.

 

There are literally thousands of cases of this happening in any field you can name, it's why (reliable) tests are needed instead of relying on (unreliable) opinions. Confirmation bias means that people aren't lying, they genuinely believe that what they hear/feel is real, even if it's not. Or it could be real, even if they believe it isn't.

 

None of which means that you're wrong, it's possible that the fan is doing what you think it is -- but your opinion doesn't prove it... 😉

I don't want to prove it! As I said, I don't care whether science proves it or not. I just want warm feet and putting a fan on the stove means that I ( and my partner) have warm feet. Even if my brain is playing tricks on me at least I still have what seem to me to be warm feet.