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Themal siphon.

 
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Hairyloon



Joined: 20 Nov 2008
Posts: 15425
Location: Today I are mostly being in Yorkshire.
PostPosted: Sat Dec 07, 13 8:37 pm    Post subject: Themal siphon. Reply with quote
    

Anyone here know how to calculate the force of a thermal siphon?
i.e. If I have a heat source about <yay big> down there, and a hot water tank up there, will the heat flow by itself, or would I need a pump to help it?

vegplot



Joined: 19 Apr 2007
Posts: 21301
Location: Bethesda, Gwynedd
PostPosted: Sat Dec 07, 13 10:15 pm    Post subject: Reply with quote
    

This may help

Woo



Joined: 19 Sep 2011
Posts: 787
Location: Mayenne, Pays de Loire
PostPosted: Sun Dec 08, 13 10:34 pm    Post subject: Reply with quote
    

i cant help with the maths but we used themo syphon the first year we had our wood burner with a back boiler. it worked, albeit a bit bangy as the pipes warmed up!(think the polar express at the door!)
we have since fitted a pump to help it get round the rads without the sound effects.
we have a cheepo grey metal stove with the back boiler. it manages to heat 6 radiators and baths for us all. the pipes are 28 mm, the bottom of the coil is about a foot above the back of the boiler. we are currently in a caravan set up so cant have too much more height!

i hope this little anecdote helps a bit?

Hairyloon



Joined: 20 Nov 2008
Posts: 15425
Location: Today I are mostly being in Yorkshire.
PostPosted: Sun Dec 08, 13 11:51 pm    Post subject: Reply with quote
    

vegplot wrote:
This may help

It gives a few clues... thanks.

Woo wrote:
i hope this little anecdote helps a bit?

A bit. Thank you too.

Ty Gwyn



Joined: 22 Sep 2010
Posts: 4562
Location: Lampeter
PostPosted: Mon Dec 09, 13 12:05 am    Post subject: Reply with quote
    

Would`nt this be the same as if you had a back boiler on a downstairs fireplace,heating a copper tank of water upstairs,

Or a central heating system,were the upstairs rads get hot ,but one needs a pump to heat the downstairs rads.

Heat rises naturally.

Mistress Rose



Joined: 21 Jul 2011
Posts: 15539

PostPosted: Mon Dec 09, 13 7:16 am    Post subject: Reply with quote
    

It would work a lot better with a pump I think Hairyloon. Is there any reason you don't want a pump?

Hairyloon



Joined: 20 Nov 2008
Posts: 15425
Location: Today I are mostly being in Yorkshire.
PostPosted: Mon Dec 09, 13 8:57 am    Post subject: Reply with quote
    

Mistress Rose wrote:
It would work a lot better with a pump I think Hairyloon. Is there any reason you don't want a pump?

Why have a pump if you don't need one?
A thermal siphon is perfectly adequate for many applications.

Mistress Rose



Joined: 21 Jul 2011
Posts: 15539

PostPosted: Mon Dec 09, 13 9:19 am    Post subject: Reply with quote
    

You will get movement by thermal syphoning, but using a pump moves the heat round faster and you won't get cold spots at the lowest points. If you run the heat source at a high temperature, there is less chance of boiling too. As you say, a thermal syphon should work, if those are not problems in your system.

Hairyloon



Joined: 20 Nov 2008
Posts: 15425
Location: Today I are mostly being in Yorkshire.
PostPosted: Mon Dec 09, 13 6:11 pm    Post subject: Reply with quote
    

Mistress Rose wrote:
You will get movement by thermal syphoning, but using a pump moves the heat round faster and you won't get cold spots at the lowest points.

I have a full central heating system here (with a pump). I have a few thoughts going around: for example turning an old freezer into an air-source heat pump, and I'm wondering if the heat will siphon effectively into the water tank by itself when the central heating is not running.

Mistress Rose



Joined: 21 Jul 2011
Posts: 15539

PostPosted: Tue Dec 10, 13 7:54 am    Post subject: Reply with quote
    

Think the only way to find out is to try it. Leave some room to put in a pump if it doesn't work well.

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