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stmbtwle

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Reply with quote  #1 
When returning heated water from the solar collector to the storage tank, should I bring it in at the top, bottom, or middle of the tank. I can see arguments for each, but curious as to which is better.  Opinions?
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Willie, Tampa Bay

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Reply with quote  #2 
Hi, Willie,

I'd say it depends on the aspect ratio (AR) of the tank, and what the tank is doing: if you have a tall tank, and it is for DHW, then definitely into the top of the tank: this will give optimal stratification.  Additionally, it is the conditions in which the water arrives that are as important: in this case, the water should not even be mixed as it comes in, it would need to be delivered over a "weir" or some other device.  Then when you run off your hot water, it is coming from the hottest part of the tank.

If the tank is for heat exchange, optimally the cold side (coil etc.) ought also to be in the top of the (stratified) tank, to give best heat exchange.

If you have a low AR tank, I'd say it did not matter where the hot comes in, since stratification will not be significant anyhow.

If you are using a low-profile tank itself as a radiant heat source, then I'd circulate it in any case (and obviously NOT insulate it !).

G_H

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stmbtwle

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Reply with quote  #3 
For the moment I'm using a 55gal (200L?) plastic drum but thinking of a 275 gal tote. I guess those would be "low" AR?
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Willie, Tampa Bay
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Reply with quote  #4 
Hi, Willie,

I posted some stuff here about tank AR...

http://simplysolar.supporttopics.com/post/importance-of-tank-aspect-ratio-on-stratification-6898208?pid=1282780036#post1282780036

I guess a cubic tote qualifies as a "squared-off circumscribed cylinder" ?

G_H

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(1)  "Heat goes from hot to cold, there is no directional bias"
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stmbtwle

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Reply with quote  #5 
Thanks for the link on tanks!

My first idea was to stand a couple drums in the room and cover them with a tablecloth, but the Admiral nixed that. So now the plan is to put drums or the tote in an insulated shed, and pump the hot water in to a heat exchanger in the room. For a collector I'm going to use a couple of swimming pool collectors laid on the roof and covered with sheet plastic. Not that efficient but they're BIG (50sq ft each). If it works through the winter I'll be happy, I'll have to remove the plastic in the spring anyway to keep from melting the collectors. If the results are good I may get more sophisticated next year.

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Willie, Tampa Bay
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