My Thermal Storage Project

[vdubnut62]

Geno, if you don't mind my asking, what are those heater cores from?
Ron

[Geno]

I don't know what car there from but here's the link. 20 bucks. Can't beat that.
# on the box: Ready-Aire 399022
http://shop.advanceautoparts.com/1/1/539396-heater-core-by-ready-aire-part-399022.html

Thanks, Geno

[mbryner]

Well, I got all excited seeing that price, thinking, "hey, why am I using copper coils instead of heater cores?"  Then I remembered: heater cores are not pressure rated for 50-60 psi.   I'd probably pop some soldered joint.   But it does make me wonder how well a heater core or radiator would work for water-water heat transfer instead of its designed use of water-air.

[Geno]

I would like to pressure test one to see what it will really handle but I'll never get around to that.

I can't see any reason why they wouldn't work well for liquid-to-liquid heat transfer. They have all that folded aluminum in there and the chimney will increase flow. Total surface area is about 4.3 sq. ft. I should have things ready for a real test in a week or two.

Thanks, Geno

[vdubnut62]

I don't know what car there from but here's the link. 20 bucks. Can't beat that.
# on the box: Ready-Aire 399022
http://shop.advanceautoparts.com/1/1/539396-heater-core-by-ready-aire-part-399022.html

Thanks, Geno

Thanks Geno!! That's cheaper than dirt.
Ron

[mobile_bob]

if you want a relatively high pressure core, look for a gm A/C evaporator core

the too are aluminum construction and should handle 50-60 psi without problems,

new they are probably expensive, but used they don't bring much.

bob g

[Lloyd]

Hey All,

Alum. doesn't survive very well in an anaerobic environment, unless it's one of the marine grades. Just a thought.

Lloyd

[vdubnut62]

Gotta be some additive or anode material or combination of the two that would stop the electrolysis. I would have thought that a fresh water
anaerobic environment would  be just peachy! However salt water would have been a disaster.
What happens Lloyd?
Ron

[Geno]

Looks like a proper PH level is the key.

http://www.floodbreak.com/default/Maintenance%20Ops/Aluminum%20corrosion%20paper.pdf

http://www.corrosion-doctors.org/MatSelect/corraluminalloys.htm

Thanks, Geno

(addition)  Based on some reading, unless my tap water is way out PH wise I should be fine in fresh water. I could get a magnesium anode for added protection. They're cheap enough. Anaerobic environments prevent the protective layer on aluminum from regenerating if it's damaged. In my application, with the materials I'm using, I don't believe there exists any way to damage this coating.

[Geno]

The hot loop from the engine room is all plumbed. The loop is refilled and bled. I had a leak at the heat ex's but double hose clamps on all the fittings fixed that. Once the loop was hot I put the heat exchangers in pic 1 in 5 gallon buckets and the results were good. I put small pieces of magnesium on the heat ex's. Second time around I did an unexpected pressure test by forgetting to open the valve to the vent/expansion/fill tank. No leaks.

Pic 2 shows the first test in the barrel. They need some weight, I don't want to take a chance of them shifting around. Should've thought of that. Good news is they're removing every BTU the engine can throw at them in this very cold water.

There is no insulation on the barrels or the new plumbing and the tops of the barrels are open. Engine load, 2400-2700 watts.
Startup temp. 0630, 9.9°c at the top of both barrels.
0730, main barrel 17.5°c, t-siphon barrel 11.2°c
0830, 23.5°c,  17°c
1045, 32.3°c, 27.8°c   Uh oh, the heat-ex barrel is warm from top to bottom but the t-siphon barrel is only warm to about 10" below the top cross connect. Hopefully it will find its groove with some more heat.

Thanks, Geno

[Geno]

Missing from first post. It's about 12.8°c in the basement. All temp readings are at the top of the barrels unless otherwise noted.
1200, Top of barrels covered.
1230, 37.5°c, 33.9°c  The t-siphon barrel is warm several inches further down and the temperature spread between them is declining.
1245, I turned on one of the heating elements. 1000 watts.
1345, 40.5°c, 37.5°c  T-siphon barrel is warm of 1/2 the way down.
1500, 44.2°c, 41.5°c  Temperature increases are decreasing, likely due to lack of insulation. T-siphon barrel is warm 2/3 of the way down.
1645, 47.4°c, 44.7c
1830, 50.1°c, 47.2°c The t-siphon barrel is somewhat warm near the bottom. 20" down it's 39°c. The heat-ex barrel is the same temp down to 20" and that's as far as my probe reaches. I thought thermosiphon would work better that this. Perhaps a small pump is in order. I'll wait and see for now and check temps in the morning to see if things equalize better. A lack of insulation skews this test quite a bit I'm sure, but all in all it was a success. It's time to shutdown and eat some leftovers.

Thanks, Geno

[Geno]

I don't know how long it took but 11 hours after I shut down the temps in the barrels were pretty much equalized. They cooled off to about 35°c and there was a .5°c difference where the temp probe could reach and I could feel by hand it was pretty close the rest of the way down. I'll have to do some more testing but I am now leaning towards a small pump to be used only while I'm adding heat. A second option would be to put one heat-ex in the t-siphon barrel. That would mean draining the system and putting longer hoses on. Draining, refilling and bleeding the system is a PITA. It would however increase efficiency due to the greater delta.

(addition) Before the t-siphon barrel warmed up there was a very distinct  boundary between the warm and cold water. It doesn't seem to make sense but I wonder if this thermocline did something to inhibit the t-siphon. My engine t-siphons just fine.

Thanks, Geno

[Ronmar]

Tha barrels are at the same height right?  One of the biggest things that powers thermosiphon is gravity.  the difference in potential from heated barrel to cool barrel is probably mostly used up in pumping the fluid across horizontally from one barrel to the other and back.    The flow is slow enough that the water gets to stratify, and that boundry layer just slowly moves downward as the barrels ultimatly equalize...

I would say yuour assessment is correct, either a small circ pump to equalize faster, or move one cooling tower to each tank.  I guess a third option would be to raise the secondary barrel up higher to improve thermosiphon flow, but that sounds like a bigger PITA than the other 2 options:(

[Geno]

Thanks Ron, I've been waiting to hear from you. Only problem is you didn't have an easy solution    Damn gravity. Works great on the engine loop though. The barrels are the same height.

I rather not have another pump. I've got enough stuff to turn on and off as it is. I've built in many options depending on what I need at the time and they're all manual. I'll soon need a clipboard to carry around with me. I'll just drain the system and do it right. Besides, I forgot to put in a couple valves for the next option. A hot water heat-ex off the wood stove in the basement.

Thanks, Geno

[Geno]

I'm done splitting the heat-ex's into each barrel. Temp spread between the barrels is only a couple degrees off now, top to bottom. The next hot water loop that goes to domestic hot water is complete. I don't get much domestic hot water yet since I can't get the barrels above 105°f without insulation but the basement is 15°f warmer because of that. No leaks yet. Some more testing and I'm ready to insulate everything.

Thanks, Geno