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Hairyloon



Joined: 20 Nov 2008
Posts: 14922
Location: Today I are mostly being in Yorkshire.
PostPosted: Wed Jan 31, 18 9:26 am    Post subject:  Reply with quote    

Nick wrote:
Yeah. I’ll recheck the figures next time it’s on.

Don't go to any much trouble: the critical temperature would be the top of the stand, which would be all but impossible to measure.
Probably just a bit too hot for the 150°C cells...

Hairyloon



Joined: 20 Nov 2008
Posts: 14922
Location: Today I are mostly being in Yorkshire.
PostPosted: Wed Jan 31, 18 9:28 am    Post subject: Reply with quote    

Mistress Rose wrote:
You would need to have all electronics and electrics well away from the heat source. I wouldn't expect domestic electronics to be useable above 125 C, or even lower. Temperature cycling is also the most stressful test for electronics, so repeat, keep them away from the heat source or they will fail quite quickly. We used to use that as a test when I was working in the industry, and short of keep turning things on and off, it was the best way to get them to fail.


As far as I can tell, all it consists of is a thermoelectric cell and a motor, both of which are situated as far from the heat as they reasonably can be.

Nick



Joined: 02 Nov 2004
Posts: 33815
Location: Hereford
PostPosted: Wed Jan 31, 18 9:31 am    Post subject: Reply with quote    

Hairyloon wrote:
Nick wrote:
Yeah. I’ll recheck the figures next time it’s on.

Don't go to any much trouble: the critical temperature would be the top of the stand, which would be all but impossible to measure.
Probably just a bit too hot for the 150°C cells...


I’ve a laser pointer thermometer. It’s easy to measure with that. As long as it’s below about 600C it’s pretty accurate.

Hairyloon



Joined: 20 Nov 2008
Posts: 14922
Location: Today I are mostly being in Yorkshire.
PostPosted: Wed Jan 31, 18 10:16 am    Post subject: Reply with quote    

Nick wrote:
Hairyloon wrote:
Nick wrote:
Yeah. I’ll recheck the figures next time it’s on.

Don't go to any much trouble: the critical temperature would be the top of the stand, which would be all but impossible to measure.
Probably just a bit too hot for the 150°C cells...


I’ve a laser pointer thermometer. It’s easy to measure with that. As long as it’s below about 600C it’s pretty accurate.

Well if you're going to be like that about it, can you do me a thermal image of a fan in operation?

Slim



Joined: 05 Mar 2006
Posts: 5184
Location: New England (In the US of A)
PostPosted: Wed Jan 31, 18 12:48 pm    Post subject: Reply with quote    

I thought those fans used Stirling engines?

Edit: nevermind, quick google showed that most are thermoelectric but there are stirling engine options

Nick



Joined: 02 Nov 2004
Posts: 33815
Location: Hereford
PostPosted: Thu Feb 01, 18 6:37 pm    Post subject: Reply with quote    

Hairyloon wrote:
Nick wrote:
Hairyloon wrote:
Nick wrote:
Yeah. I’ll recheck the figures next time it’s on.

Don't go to any much trouble: the critical temperature would be the top of the stand, which would be all but impossible to measure.
Probably just a bit too hot for the 150°C cells...


I’ve a laser pointer thermometer. It’s easy to measure with that. As long as it’s below about 600C it’s pretty accurate.

Well if you're going to be like that about it, can you do me a thermal image of a fan in operation?


No.

But I can paint a thermal picture with numbers, if that helps.

Fire is on. Fan started turning when the cowl it sits on got to about 100. Base of the fan is that. Body of be fan, the rotating parts and the blades for heat transfer were about 45.

Fires running well now, on a reasonably low heat and the cowl is 180, fan base is around 145 and the other parts about 70.

All values in degrees C.

Hairyloon



Joined: 20 Nov 2008
Posts: 14922
Location: Today I are mostly being in Yorkshire.
PostPosted: Fri Feb 02, 18 12:07 pm    Post subject: Reply with quote    

Thank you. Very helpful. Looks like the 150°C cells will probably cope, which is handy 'cos I have one here (somewhere).
I don't suppose you are able to measure the top of the stand? Effectively the hot side of the cell. I imagine it's a bit tricky to do so don't go to trouble, but I'm curious about the rate of heat transfer up the stem compared to the heat lost from the stem, if that makes sense.

Nick



Joined: 02 Nov 2004
Posts: 33815
Location: Hereford
PostPosted: Fri Feb 02, 18 1:58 pm    Post subject: Reply with quote    

I’ll try and remember next time it gets cold and I’m here.

Hairyloon



Joined: 20 Nov 2008
Posts: 14922
Location: Today I are mostly being in Yorkshire.
PostPosted: Fri Feb 02, 18 8:51 pm    Post subject: Reply with quote    

As I said, don't go to trouble: is just curiosity now.

Slim



Joined: 05 Mar 2006
Posts: 5184
Location: New England (In the US of A)
PostPosted: Mon Feb 05, 18 9:35 pm    Post subject: Reply with quote    

Google must have remembered that I looked up stirling vs. thermoelectric stove fans. They've just suggested this scrapheap challenge DIY stove fan video to me (seems to be one of many out there): https://youtu.be/1u7POtVxtMI

Hairyloon



Joined: 20 Nov 2008
Posts: 14922
Location: Today I are mostly being in Yorkshire.
PostPosted: Tue Feb 06, 18 2:52 pm    Post subject: Reply with quote    

Slim wrote:
Google must have remembered that I looked up stirling vs. thermoelectric stove fans. They've just suggested this scrapheap challenge DIY stove fan video to me (seems to be one of many out there): https://youtu.be/1u7POtVxtMI


I thought it was a really clever Stirling engine when I saw the chainsaw cylinder. Disappointed to find it was just being a cooling device.

Did like his explanation of how the thermoelectric cell works.

Slim



Joined: 05 Mar 2006
Posts: 5184
Location: New England (In the US of A)
PostPosted: Tue Feb 06, 18 5:33 pm    Post subject: Reply with quote    

I was hoping he would use the pipe fitting that held the fan as a "chimney" with fan assist to draw air directly over the thermoelectric cell for better cooling the cool side. The fan still basically did that, I just wanted to see some extra flourishes I guess.

I also thought it was going to be stirling at first

dpack



Joined: 02 Jul 2005
Posts: 33718
Location: yes
PostPosted: Tue Feb 06, 18 8:06 pm    Post subject: Reply with quote    

a stirling that small might be a bit beyond scrapheap challenge.

scale matters when it comes to coefficients of friction, longevity of tolerences, etc etc.

my point is small and moving requires supergood engineering in general as well as in relation to energy harvest by mechanical means.
solid state stuff making leccy works well for small machines

pop a fan on the drive of a chainsaw and cut out most of the faff?

Mistress Rose



Joined: 21 Jul 2011
Posts: 9622

PostPosted: Wed Feb 07, 18 8:08 am    Post subject: Reply with quote    

I would agree with you Dpack. Having been fighting tolerances and coefficients of expansion most of my working life in microelectronics I understand the problem.

dpack



Joined: 02 Jul 2005
Posts: 33718
Location: yes
PostPosted: Wed Feb 07, 18 10:50 am    Post subject: Reply with quote    

rolex and t34 demonstrate the different approaches depending on scale. both are complex machines but one can be mended in a barn with a gas torch, half a dozen stout tools and a big hammer, the other needs a microscope, a cleanroom and a very steady hand.

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