Stratification Report

[jebatty]

I just put in operation a 1000 gal LP tank for storage, approx dimensions are 3'D x 19'L. I draw water from the bottom drain fitting and return hot water to top of tank. The tank is insulated with 6" fiberglass. With this diameter, I am finding minimal stratification, 10-20 degrees, as the tank heats. So far I have only heated to about 140F. Example: 170F supply to tank, 120 return from tank, tank temperature 130-135. The 170F water seems to quickly disperses in the tank rather than stay towards the top.

What experience have others had on tank diameter or height and degree of stratification?

I have some more trials to run and will report more if further experience shows a material difference.

In my application the minimal stratification is OK for heating purposes, but a greater level of stratification would be better in regard to pulling heat off the boiler without cycling. At lower return temp to boiler there is essentially no cycling, but as return temp rises, cycling begins to occur. A variable speed pump with more volume at higher temp, or just a higher volume pump in general, might work to reduce cycling.

 

[SciGuy]

Jim,

How does the hot water enter? Is it entering straight down? this would cause a great amount of mixing and therefore little stratification. Perhaps you can rig a fitting to send it at 90 degrees to stay at the top of the tank.

Hugh

 

[jebatty]

Good idea -- it is straight down, and I can try the horizontal fitting. Thanks.

 

[sled_mack]

Same thing with the return - if it pulls down you may want to add a fitting there.

Also, where are the supply/return fitting relative to each other? If close to each other (horizontally, as one is top and one is bottom), it may lead to a more direct path of the water. Having them at opposite ends of the tank may give better stratification, just in terms of the flow path of the water.

I know something 19 ft tall is impractical, but that would give ideal results for stratificaiton. My tank is 10 ft across and 5 ft high, and it is hard to get good stratification in it. It seems to want to heat soak the whole way through. But, mine has coils, not pressurized.