stratification idea for unsealed storage

[pybyr]

I'm hoping to get feedback on this (also hoping the technology cooperates in my first effort to post a graphic)(excuse my non-artist skills!)

since I am ending up going with non-pressurized storage, I want to make particular effort to have the inflows and outflows of the tank occur in a way that maximizes stratification, and does not mix the tank's contents all around.

below, depicted in my crude sketch, is the concept, which would be:

a round large diameter (6-8 inch?) hollow vertical column in the center of the tank, with a horizontal partition at its vertical midpoint, and one ring of holes around the perimeter near the bottom, and another ring of holes near the top, not too far below the water level. intake and suction pipes enter these upper and lower chambers.

"hot" intake and outlet pipe is on left, "cold" is on right

The idea/ hope is that by having the intake and suction pipes enter these larger chambers, velocity of flow will be greatly reduced where the flow "meets" the tank as a whole- to avoid "stirring up" the tank. Having the ring of holes at top/ bottom of the large diameter column will cause water to be pushed to or drawn from the places where the temperature differential is greatest. Horizontal partition in the middle of the vertical column will keep the intake and outflows from mixing Having this all in the middle seems like the place to have it, since the tank's sides, being naturally coolest (even with insulation) will have their own convection going on.

reactions, ideas, suggestions? fire away, please!

 

[free75degrees]

I think the most important part is to set it up so that you can tweak it and experiment with it. Fluid dynamics and heat flow are so complicated that it would be really hard to predict the outcome. The best route may be to use trial and error.

 

[in hot water]

sounds workable. I saw a bunch of different stratification tank concepts at a solar show recently. Most had cylinders as you describe. Another common feature is a small vessel near the top for DHW generation. Tank companies are trying to get away from large storage of DHW for hygienic reasons, aka Legionella. Either a small tank or a large stainless steel corrugated coil for DHW generation.

Another concept uses a phase change material in an open tank to try and capture latent heat from humidity in the room. Wild ideas floating around the think tanks, pun intended, over in Europe.

Some of these tanks are making their way to the US. 4 grand and up seems to be the price!

hr

 

[Willman]

It seems the Euros prefer vertical tanks. Do you think it is for space savings or better stratification ?

Will

 

[Hansson]

It seems the Euros prefer vertical tanks. Do you think it is for space savings or better stratification ?

Will

Better stratification ! A system whit bad stratification is a bad system

 

[jebatty]

Maybe someone with a large tank with multiple sensors actually knows what's happening during a charge cycle. My tank probably achieves minimum stratification by reason on height. It's 19'-L by 3'-diameter. Inlet is 4" from the top and about 1/3 from and end, and is an L to direct water flow to the opposite end of the tank. Outlet is same end as the inlet, but on the bottom and very end of the tank.

I have a thermometer which reads input temp and tank outlet temp, and there always is large temp difference between these two, which gradually narrows as the tank charges. There appears to be considerable stratification occurring.

This fall when the boiler is again fired up I will add sensors at different points along the top and bottom of the tank to see better as to stratification. I have no ability to add sensors midpoint inside the tank.

 

[Hansson]

To get stratification when you load the tank is not so hard.
The hot water goes naturally to the top of the tank.Slow flow is important
If you have a vertical tank you get a longer distance.Hope you know what i mean :-(

Its when you unload it it`s important to get good stratification.

If i cold rebuild my system i wold make the hot water outside the tank whit a hx.
Like this one.Then you get good stratification
(broken link removed to http://www.baxi.se/visa_produkt.asp?produktid=25&Kategori=7&Produkttyp=2)