Homespun
03-22-2015, 07:48 AM
This formula is from a HVAC forum. I'm not confirming its accuracy, but just passing it along.
1 gallon of water = 8.33 lbs
To take 1 lb of water from 32 F degrees F to 220 F degrees steam temperature in an open container:
180 BTUs needed to take 32 F water to 212 F water
+ 970 BTUs needed to take 212 F water to 212 F steam
+ 5.376 BTUs needed to take 212 F steam to 220 F steam (constant pressure in an open container)
1,155.376 BTUs total needed per pound of water
1155.376 BTUs X 8.33 lbs (the weight of 1 gallon of water) = 9,624.82 BTUs is required to raise 1 gallon of water from 32 F degrees to 220 F steam temperature
Rounded up, 9,625 BTUs per gallon are needed to actually be absorbed by the water itself, to take it from 32 f degrees to 220 f degrees steam.
If 1 gallon of 32 f degree water absorbs 9,625 BTUs in one hour, it is boiling away at 1 GPH
If 1 gallon of 32 f degree water absorbs 19,250 BTUs in one hour, it is boiling away at 2 GPH
If 1 gallon of 32 f degree water absorbs 28,875 BTUs in one hour, it is boiling away at 3 GPH
and so on...
I have no idea on how to calculate how much heat from the burner is actually wasted away as exhaust or flowing around the pan and not being absorbed by the water in the pan...or the heat loss of the pan to the surrounding air as you're heating it...or heat being absorbed by the surrounding equipment or downwards to the ground.
That being said, I'll guesstimate that maybe we're only 20% efficient...only 20% of the heat we supply actually gets absorbed by or transferred into the water, so the above BTUs per hour would need to be multiplied by 5.
If this is the case, the BTUs/hour input required, at 20% efficiency (80% wasted heat) would be:
1 gallon of 32 f degree water needs 48,125 BTUs heat supplied in one hour, to boil away at 1 GPH
1 gallon of 32 f degree water needs 96,250 BTUs heat supplied in one hour, to boil away at 2 GPH
1 gallon of 32 f degree water needs 144,375 BTUs heat supplied in one hour, to boil away at 3 GPH
and so on...
If you have water warmer than 32 f degrees to boil away, less heat input is required to boil it away... or more GPH will result (pre-heated or warmed water will increase the efficiency).
If you increase the amount of heat the water absorbs by trapping it, funneling it, focusing it, or forcing it into the water, less heat input is required to boil it away... or more GPH will result.
1 gallon of water = 8.33 lbs
To take 1 lb of water from 32 F degrees F to 220 F degrees steam temperature in an open container:
180 BTUs needed to take 32 F water to 212 F water
+ 970 BTUs needed to take 212 F water to 212 F steam
+ 5.376 BTUs needed to take 212 F steam to 220 F steam (constant pressure in an open container)
1,155.376 BTUs total needed per pound of water
1155.376 BTUs X 8.33 lbs (the weight of 1 gallon of water) = 9,624.82 BTUs is required to raise 1 gallon of water from 32 F degrees to 220 F steam temperature
Rounded up, 9,625 BTUs per gallon are needed to actually be absorbed by the water itself, to take it from 32 f degrees to 220 f degrees steam.
If 1 gallon of 32 f degree water absorbs 9,625 BTUs in one hour, it is boiling away at 1 GPH
If 1 gallon of 32 f degree water absorbs 19,250 BTUs in one hour, it is boiling away at 2 GPH
If 1 gallon of 32 f degree water absorbs 28,875 BTUs in one hour, it is boiling away at 3 GPH
and so on...
I have no idea on how to calculate how much heat from the burner is actually wasted away as exhaust or flowing around the pan and not being absorbed by the water in the pan...or the heat loss of the pan to the surrounding air as you're heating it...or heat being absorbed by the surrounding equipment or downwards to the ground.
That being said, I'll guesstimate that maybe we're only 20% efficient...only 20% of the heat we supply actually gets absorbed by or transferred into the water, so the above BTUs per hour would need to be multiplied by 5.
If this is the case, the BTUs/hour input required, at 20% efficiency (80% wasted heat) would be:
1 gallon of 32 f degree water needs 48,125 BTUs heat supplied in one hour, to boil away at 1 GPH
1 gallon of 32 f degree water needs 96,250 BTUs heat supplied in one hour, to boil away at 2 GPH
1 gallon of 32 f degree water needs 144,375 BTUs heat supplied in one hour, to boil away at 3 GPH
and so on...
If you have water warmer than 32 f degrees to boil away, less heat input is required to boil it away... or more GPH will result (pre-heated or warmed water will increase the efficiency).
If you increase the amount of heat the water absorbs by trapping it, funneling it, focusing it, or forcing it into the water, less heat input is required to boil it away... or more GPH will result.