Several prior posts of mine have demonstrated the extreme stratification in a 1000 gallon horizontal storage tank (19' x 3'). In my application, it seems that stratification only matters when charging the tank, because that's the only time it is important to keep the delta-T as high as possible for as long as possible to insure the most efficient operation of the boiler by keeping it at full burn and without idle cycling. This seems to be best accomplished by maintaining as low a flow as possible which still keeps the boiler from idling. My system accomplishes this goal.
But stratification during the draw down is another matter. My only hot water draw is heating a 1500 sq ft concrete radiant floor. Others may have a similar situation. I am easily able to heat the storage to 185-190F, top to bottom. The mixing valve is set to deliver hot water to the floor at 100-105F, and heat from storage still functions well with a draw down to as low as 85F, the lowest I've gone so far, although this winter my normal boiler firing occurs when storage drops to about 100F, and firing is occurring every 2-3 days. In this scenario, there is little benefit to maintaining stratification during the draw down.
I've noticed that during draw down considerable mixing occurs in the tank. Between draw downs the tank quite quickly re-stratifies with about a 10F temperature difference between the top and bottom, with only the very bottom 6" or so having the low temperature and everything above being very close to the high temperature. The tank is quite well insulated.
I have been logging boiler/storage performance, as well as floor, inside, and outside temperatures, and wood consumption by weight, nearly continuously since the beginning of November. This will present the best data picture yet which I have of real world performance in a cold climate.
But stratification during the draw down is another matter. My only hot water draw is heating a 1500 sq ft concrete radiant floor. Others may have a similar situation. I am easily able to heat the storage to 185-190F, top to bottom. The mixing valve is set to deliver hot water to the floor at 100-105F, and heat from storage still functions well with a draw down to as low as 85F, the lowest I've gone so far, although this winter my normal boiler firing occurs when storage drops to about 100F, and firing is occurring every 2-3 days. In this scenario, there is little benefit to maintaining stratification during the draw down.
I've noticed that during draw down considerable mixing occurs in the tank. Between draw downs the tank quite quickly re-stratifies with about a 10F temperature difference between the top and bottom, with only the very bottom 6" or so having the low temperature and everything above being very close to the high temperature. The tank is quite well insulated.
I have been logging boiler/storage performance, as well as floor, inside, and outside temperatures, and wood consumption by weight, nearly continuously since the beginning of November. This will present the best data picture yet which I have of real world performance in a cold climate.