Storage Tank Line Location

[George Webster]

I am trying to figure out the best location for my supply (hot) and return (cold) lines to my storage tank. The tank has 4 openings on the top, one at each end and two located about 18" apart near the middle. Nofossil thinks I should run the lines at the middle of the tank, with a tee on the bottom of each line so that the water gets directed out in both directions, horizontally, encouraging stratification. This places the lines as close as possible to one another and I'm a little concerned about heating the return water and at the same time cooling that close to the hot line, since the return will be in close proximity. My thought is to place the supply at the middle of the tank with the tee to direct water in both directions, but to have the return located at the far end of the tank where it won't have such an immediate effect on water in close proximity to the supply. Any thoughts on this will be greatly appreciated, as I have no experience with how this will work. Nofossil has a tank with internal exchange coils, so it is far different than mine. As a result, we're both kind of guessing at what might work.

 

[maple1]

So you're talking about using a dip tube on your return?

EDIT: Are there any fittings at all on the bottom of the tank? Mine had a very handy 1-1/4" one.

 

[George Webster]

So you're talking about using a dip tube on your return?

EDIT: Are there any fittings at all on the bottom of the tank? Mine had a very handy 1-1/4" one.

Unfortunately not. I decided to go with the lines close - as long as they need to drop down from the top I'm, not sure it makes that much difference. Having a tee which allows the water to flow in both directions would seem to reduce turbulence and help the stratification, so we'll see how it performs.

 

[goosegunner]

So is one of the middle lines a dip tube?

If so I doubt you would get much mixing if you use adequate pipe size to move water at low velocity. Once you are running it will make more sense but it is amazing to feel the tank as it charges. The stratification is very apparent. I think it would be very hard to pull the hot water down into the cold return water to the bottom of the tank.

If you're still concerned you could use both ends. Buy double tap bushings, put a short section in one end for supply and a longer pipe in the other end to pull return water from the bottom of the tank.

gg

 

[George Webster]

So is one of the middle lines a dip tube?

If so I doubt you would get much mixing if you use adequate pipe size to move water at low velocity. Once you are running it will make more sense but it is amazing to feel the tank as it charges. The stratification is very apparent. I think it would be very hard to pull the hot water down into the cold return water to the bottom of the tank.

If you're still concerned you could use both ends. Buy double tap bushings, put a short section in one end for supply and a longer pipe in the other end to pull return water from the bottom of the tank.

gg

Basically, there are two openings near the middle of the tank, at the top, about 16" apart, with dip tubes in each one. One dip tube extends to the bottom of the tank to 1" off the bottom - this is the return. At the top, there is another line that will terminate near the top of the tank. Both lines are 1" copper with a 1" tee at the end of the pipe and about 3" of 1" copper extending from each end of the tee, to slow the velocity even further and distribute the water in both directions horizontally across the length of the tank. My concern is heat transfer to the return water as it passes through the dip tube to the bottom of the tank, especially since it is in such close proximity to the supply line, where the water will be the hottest. I know, anal. Since it is a short tube - about 45", there shouldn't be appreciable transfer.

 

[goosegunner]

What size boiler are you using? 1" seems small for the output of most gasifiers.


Once you feel your tank as it heats I think you will see that your concern won't matter that much. Using a dip tube for the return anywhere on the tank would have the same effect.


It would be interesting to monitor bottom of tank temps compared to return right before thermal protection to see how much it is warming the water as it passes through the hot layer on its way to boiler.

gg
gg