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Hot water storage tanks?
By Number21, Section Heat Posted on Wed Oct 21, 2009 at 03:44:32 AM MST
How hot should they be?

I'm moving into a new shop with a wood stove for heat. I would like to use the stove to heat up water, which would then continue to heat the shop continuously even when the fire has long gone out. I'd like to use steel 55 gallon barrel(s) to store the hot water in. If I use a glycol based "coolant" in the barrels it would keep them from rusting and allow me to store water at above 212 degrees. I will then pump the hot water through a radiator and through another heat exchanger for my electric water heater.
My question is, how hot should I store the water? I'm not sure how much I'll need yet, but, I can always add more barrels to the system. Should I bother going much above 200 degrees?
Also, how much glycol cooling mix would I need in the barrels to keep them from rusting out? 25%? 10%?

Hot water storage tanks? | 4 comments (4 topical)

Re: Hot water storage tanks? (3.00 / 0) (#1)
by electrak on Wed Oct 21, 2009 at 04:56:45 AM MST

10% will get you to 214F
20% will get you to 216F
30% will get you to 219F
40% will get you to 221F
50% will get you to 225F
60% will get you to 232F
Specific Heat Capacity
25% is 0.953
50% is 0.865
100% is 0.66

So as to have some safety, I would target about 180-190F. Now if you pressurize it you can go hotter, but do not use 55 gallon drums, keep them vented, and if you are using Ethylene Glycol, vent it outside, that sweet smell is antifreeze condensing in your nose, from there it goes into your blood, breathing that all day is not good.
You can get Propolene Glycol, the stuff for RV tanks, and get a crosion preventer mix. then in small amounts it's not deadly.

Re: Hot water storage tanks? (3.00 / 0) (#2)
by BigBreaker on Wed Oct 21, 2009 at 08:45:07 AM MST

Check out builditsolar.com - Gary has some great plans for hot water storage tanks. The liners can't handle 200F but you may want to consider a lower, safer temperature.

[ Parent ]

Re: Hot water storage tanks? (3.00 / 0) (#3)
by bob g on Wed Oct 21, 2009 at 11:33:27 AM MST

if all your after is rust inhibitor, use a DCA fluid
and forget the antifreeze.

its relatively inexpensive and a pint can treat something like 10 gallons
or more.

you can get it from any heavy truck dealer, so shop around for the best price.

bob g

Re: Hot water storage tanks? (3.00 / 0) (#4)
by scottsAI on Wed Oct 21, 2009 at 07:36:28 PM MST

Alternative

Rocket stove
http://en.wikipedia.org/wiki/Rocket_stove
Better diagram of it:
http://www.permies.com/permaculture-images/1078_150/rocket_stove_butt_warmer_3.gif

Have fun,
Scott.

Hot water storage tanks? | 4 comments (4 topical)

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