William Bronson wrote: Wow 275 is huge
Yes, that was . It was what I had at the time and I figured if I was trying to heat 10,000 gallons at one burning, I might have to go big! remembering back, it got to 119F under the rock wool at the very top as it was stratifying. The water may have started at 50F. It would take a lot of figuring at different levels of stratified temperatures to figure the BTU captured. I cannot take the time for that right now. I'm sure it's going to do the same for me in the big tanks. I believe I'm going to have to use pumps to circulate the water to mix it to de-stratify the water since I cannot have water above 140F in any one part of the tank as the poly tank can become weak and may leak. If mixed, I don't believe it will stratify. I have not found any evidence to the contrary. If there is, I will have to reconsider my options as I am off grid and do not want to operate pumps full time to keep the water mixed.
As far as the heating tank or coils, I don't want to go too awfully big as it will be expensive for the materials, and too much heat will be lost in the process of heating the water. I may be wrong. I'm thinking I could make the entire room that the tanks would be a part of would be a "bell". Not only would the boiler be heating water directly, but the exhaust could envelop the tanks to heat them from the outside. Having over 800 sq ft of heating area of the outside of the tanks would definitely help in warming the water. Then I get back to the poly not being being able to be exposed to temperatures above 140F. Alas, I have crazy thoughts and should not entertain them.
A 6" batch stove at 77,000 BTU would take 32.5 hours at 90% efficiency to create 2,500,000 BTU. Now, that would be three 10 hr days of burning which I'm fine with. But, how efficiently can I transfer 2,500,000 BTU to water? If I am only 70% efficient that means I have burn another 14 hrs (1.5 days) to save enough of the 3,600,000 BTU. If I can cut losses to 15% instead of 30%, I can save 1/2 a day burning.
I know it sounds like a complicated process to be able to cut burn time to a minimum and I could do it with a smaller tank system, but I'm looking to heat a 1500 sq ft house, possibly two houses, a 750 sq ft utility building and a 1600 sq ft greenhouse for fresh winter product for 2 families.
As I see it, i need to now determine boiler size (BTU), material and type of heat exchange and if the water will stay de-stratified once mixed. Perhaps, the most important part of this will be the latter. If the water will not stay mixed, I cannot operate mixing pumps full-time...mooting the first two questions of BTU output and heat exchange.
Lunch is over. Time to go back to work. Thank you for making me think.