Tank stratification - how long does it take?

[MrEd]

Lets assume you are just blasting hot water into your 500 gallon propane tank without regard for how it will stratify (lets assume worst case even that you are pumping hot water into the bottom of the tank).

It will eventually stratify itself, no? How long would it take?

 

[deerefanatic]

Oh, it WILL stratify itself..... Pumps and such are no match for mother nature! As for how long, I would swing a (totally random) guess at about an hour...........

 

[Nofossil]

In my experience, it won't startify at all unless you're adding or removing heat. If you get it thoroughly mixed at a given temperature and don't remove any heat, it will stay uniformly mixed. If you let it cool (due to inadequate insulation, for instance) it will begin to stratify as the cooler water from the outside flows downwards and collects in the bottom.

 

[deerefanatic]

Ok, makes sense.... You definitely have more hands on knowledge of this than I do.

 

[DaveBP]

Nofossil is right. If you are not adding or removing heat the water won't stratify if it is not already stratified.

Heat does not rise. Gases and liquids that are less dense will rise. That is usually the warmer liquids and gases that rise but the heat itself conducts down as easily as up. Water is densest at 39F so water warmer or colder than that will rise. The warmest water in a frozen-over pond (39F) is on the bottom. Gotta love those apparent paradoxes.

In fact, I'll see Nofossil and raise him one. I contend that if the water in the storage tank is highly stratified and closed off and insulated enough to not be losing much heat it will de-stratify and become a uniform temperature throughout. The hot water on top will heat the adjacent water below it until it's all the same temp.

Any real physics people out there?

Anybody up after 1AM thinking about this stuff definitely has the bug.

 

[WoodNotOil]

DaveBp - I believe it is the thermocline that separates the stratified layers and prevents a well stratified tank from mixing.

 

[Huskurdu]

Someone please give a definition of 'stratification'. I took a vacation day yesterday to play with my Econoburn 150. I had it heating my 500 gallon pressurized storage. The lines attach to the end of the tank towards the top. I felt the take periodically and it was interesting how the heat slowly worked its way to the bottom of the tank. It was so hot on top that you could barely hold you hand on it, but the bottom was totally cold. This morning it was finally all 'warm', appararently the E-burn ran out of wood before my house and tank were warm. Now that the storage is at about 100-110 degrees maybe the E-burn will catch up today!

 

[Nofossil]

Someone please give a definition of 'stratification'. I took a vacation day yesterday to play with my Econoburn 150. I had it heating my 500 gallon pressurized storage. The lines attach to the end of the tank towards the top. I felt the take periodically and it was interesting how the heat slowly worked its way to the bottom of the tank. It was so hot on top that you could barely hold you hand on it, but the bottom was totally cold. This morning it was finally all 'warm', appararently the E-burn ran out of wood before my house and tank were warm. Now that the storage is at about 100-110 degrees maybe the E-burn will catch up today!

Stratification is exactly what you describe - the situation where water at the top is much hotter than water at the bottom, ideally with a sharp transition called a thermocline.

Stratification is desirable because it increases the effective storage capacity.