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Eco Fan


mrsmelly

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Wiki says: "While air movement can be pleasant and provide comfort in some circumstances, it is sometimes unwanted and causes discomfort. This unwanted air movement is called "draft" and is most prevalent when the thermal sensation of the whole body is cool. People are most likely to feel a draft on uncovered body parts such as their head, neck, shoulders, ankles, feet, and legs, but the sensation also depends on the air speed, air temperature, activity, and clothing" (my emphasis).

There must be a cross-over between the comfort felt from the convection and the discomfort from the draught. At what air speed would you suggest that crossover occurs?

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2 hours ago, mark99 said:

 

10 feet away I would be sitting in the cratch outside the front door.

"While the physics are relatively complex, air stratification is a basic layering effect that allows large air pockets with different core temperatures to remain intact, regardless of whether the building's central HVAC system is running"

If you had the Stirling Engine going the bone may have been rotating so fast you would not have noticed it.  ;)

 

Still no credible answer from the wider crew why 3m3/min of air circulating does not help even out temps in front of stove. But lots of avoidance and random opinions.

The credible answer is " Placebo effect " as I stated in an earlier post. It is a very real and recognised thing.

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1 minute ago, mross said:

'Wind chill' only applies when the air is colder than you.  Or if your clothes are wet.

Yes totally correct. But what temperature are you? From your avatar I guess you are less than 20degC but I am 39deg C ish. Air flows of 20-25deg will cool. Ever tried sailing in the Med? Stiffling sat in the sea in no wind (in the shade) but when the wind starts, it is great - all at 30deg C. At around the 20-25deg our cabin is normally, it is more comfortable not to feel the draught. I would not want a 12 volt computer fan blowing at me. Try it, you will feel a draught.

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4 minutes ago, Dr Bob said:

Yes totally correct. But what temperature are you? From your avatar I guess you are less than 20degC but I am 39deg C ish. Air flows of 20-25deg will cool. Ever tried sailing in the Med? Stiffling sat in the sea in no wind (in the shade) but when the wind starts, it is great - all at 30deg C. At around the 20-25deg our cabin is normally, it is more comfortable not to feel the draught. I would not want a 12 volt computer fan blowing at me. Try it, you will feel a draught.

You would feel a draught with a computer fan that's because it actualy does something.

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I learnt all about windchill on a motorcycle; even on a warm day you can get chilled at 70mph in the UK.  In California, in their summer, I often put a leather jacket on to stop the warm air from making me too hot!

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6 minutes ago, Machpoint005 said:

Wiki says: "While air movement can be pleasant and provide comfort in some circumstances, it is sometimes unwanted and causes discomfort. This unwanted air movement is called "draft" and is most prevalent when the thermal sensation of the whole body is cool. People are most likely to feel a draft on uncovered body parts such as their head, neck, shoulders, ankles, feet, and legs, but the sensation also depends on the air speed, air temperature, activity, and clothing" (my emphasis).

There must be a cross-over between the comfort felt from the convection and the discomfort from the draught. At what air speed would you suggest that crossover occurs?

Now that I totally agree with. Yes there must be a cross-over, which is exactly my point. If I am sat in the front cabin at 10ft from the stove, I dont want to feel an air flow - so a 12v fan would be bad. I dont know what the crossover is, but I do know that the fan produces an environment that is more comfortable than without it as my feet are not as cold and the temp feels more even. What I feel is pretty much in line with the heat maps produced earlier in  the thread which will have been based on 10,000 temperature recordings per run.

I think the crossover will vary person to person and that is why there is so much 'positioning' on this thread. It is not as easy to see on this thread but if you look at the first page of the other one, there are quite a few early respondents who acknowledge both low fan effectiveness but with improved thermal comfort.

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3 minutes ago, Dr Bob said:

What I feel is pretty much in line with the heat maps produced earlier in  the thread which will have been based on 10,000 temperature recordings per run.

Where does the report say they took 10,000 readings!  It's implied that they recorded them manually; they even show the log sheets!  A heat map is a snapshot and can't use more readings than the number of sensors, which was about 20 iirc.

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20 minutes ago, mross said:

Where does the report say they took 10,000 readings!  It's implied that they recorded them manually; they even show the log sheets!  A heat map is a snapshot and can't use more readings than the number of sensors, which was about 20 iirc.

Co'mon, keep up. I pointed you at this earlier in the thread. In Appendix 2, it lists the 56 thermocouple probes connected to their data logger. Each run was 3 hrs (=180 minutes) and they took a temperature recording every minute. They list the position of each probe. Runs were done in pairs, one with a fan and one without. During a run they would therefore have recorded 56 results per minute which by my calculation (multiply by 180) says 10,000 readings ish (actually 10,080 which sounds like an extraordinary high darts shot).

The heat map would have used a set of the 56 readings to compute a 2d and 3d picture of the room from the simulation software – of which we are only seeing a 2d image.

What has not been discussed from that paper is the claim of 15% fuel saving. Other than 'dissing' the whole paper, I've not heard any constructive comments on what they have done wrong to come to that conclusion. I, like you, cannot believe a fuel saving.

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They may have accumulated 10,000 readings although some of the sensors were not temperature sensors inside the room and can't have contributed to the heat map.  The heat map is a cross-section of the room down its centerline - but most of the sensors were on the ceiling and walls.  there is no mention of a 3d analysis and they produce no heat maps to support any 3d analysis.   The report is dated July 2010 and a follow up report was mentioned.  Let's try and find it!

Although they had an anemometer, they never measured the airflow from the Ecofan!

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30 minutes ago, Dr Bob said:

What has not been discussed from that paper is the claim of 15% fuel saving. Other than 'dissing' the whole paper, I've not heard any constructive comments on what they have done wrong to come to that conclusion. I, like you, cannot believe a fuel saving.

Maybe because we are pretty well all agreed that it's very unlikely? An unsubstantiated claim like that must cast some doubt on the veracity of the rest of the 'paper' too. 

8 minutes ago, mross said:

Although they had an anemometer, they never measured the airflow from the Ecofan!

In which case, what does the quoted cfm figure relate to? The anemometer would measure velocity and you need an area to calculate the volume flow rate through it.

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3 minutes ago, mross said:

They may have accumulated 10,000 readings although some of the sensors were not temperature sensors inside the room and can't have contributed to the heat map.  The heat map is a cross-section of the room down its centerline - but most of the sensors were on the ceiling and walls.  there is no mention of a 3d analysis and they produce no heat maps to support any 3d analysis.   The report is dated July 2010 and a follow up report was mentioned.  Let's try and find it!

I counted 56 temperature sensors out of the 60 plus 'tags'. Maybe I miss counted. Ive only got 20 fingers and toes. Some of the sensors were outside the room but suspect they would help in the heat modelling in calculating losses through the walls - but obviously not as relevant to the 'internal' probes (hence a proportion of the 10K readings would be less important :)).

I know you have been saying there is a second paper but I never saw that comment. What page was that on? I was confused that the overall paper - 40 odd pages - (havent got it open at the moment) seemed to be made up of 2 papers, the first saying what they were going to do and the second (after the set of appendicies) with the results. I wonder then, is the second part - the second paper you mention?

I will do a bit of searching for more papers.

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3 minutes ago, Machpoint005 said:

Maybe because we are pretty well all agreed that it's very unlikely? An unsubstantiated claim like that must cast some doubt on the veracity of the rest of the 'paper' too.

The claim was not unsbustantiated. They provided data that they assumed to 'prove' the claim. As a scientist with lots of experience in writing and reviewing papers, I gave some criticism earlier in the thread that would have helped more in the proof - but it is possible that they did have the proof. As it was 10 years ago, it is now impossible to question the paper. No one (other than Mross) has tried to discuss the paper. Yes, I think there is doubt based on the comments I made  (and Mross made) but it would be wrong to 'flush it down the loo' and say rubbish without more reasoned debate. The information on fuel usage actually seems quite robust. We need to see the follow up paper.

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http://www.ecofan.ch/pdf/Studie_Energieeinsparung_Ecofan_komplett.pdf

for anyone looking for the report.

On page 9, it says, "The authors intend to design and conduct improved experiments in the fall of 2010 to adequately quantify advantages of using a fan when used with a wood stove. The new experiments will be conducted in a test facility with improved controlled environment that allows for below 0°C settings."

Edited by mross
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4 minutes ago, Dr Bob said:

The claim was not unsbustantiated. They provided data that they assumed to 'prove' the claim. As a scientist with lots of experience in writing and reviewing papers, I gave some criticism earlier in the thread that would have helped more in the proof - but it is possible that they did have the proof. As it was 10 years ago, it is now impossible to question the paper. No one (other than Mross) has tried to discuss the paper. Yes, I think there is doubt based on the comments I made  (and Mross made) but it would be wrong to 'flush it down the loo' and say rubbish without more reasoned debate. The information on fuel usage actually seems quite robust. We need to see the follow up paper.

Please do NOT flush it down the loo if its a macerator or you may need to harness the unbridled power of an " Eco fan " as a pump to clear the blockage.

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1 minute ago, mross said:

The report states fuel savings but gives no 'margin of error'.  It has not been published in any peer-reviewed journal or industry magazine or even in Practical Boat Owner!

Unfortunately they were unable to replicate their results after being forced to abandon the experiment when one of the Ecofans broke loose and destroyed the lab.

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