How to Determine the Amount of Steam Required for Heating Water
To determine the amount or steam required to heat a specified quantity of water using steam at atmospheric pressure (212° F) either in a heat exchanger* or by direct injection.
(Gallons of water) x (Pounds per gallon) x
(Temperature rise in ° F.) = Pounds of steam
(Latent Heat of steam / Btu’s)
Example: To determine the amount of steam required to heat, 300 gallons of water form 60° to 160° F. in one hour with steam at atmospheric pressure—gallons of water = 300 x pounds per gallon (8.3 lbs.) x temperature rise (100° F.) ÷ latent heat of steam (970 Btu’s)
300 x 8.3 x 100 = 257 pound of steam per hour
Divide 257 by 34.5 (one boiler horsepower = 34.5 pounds of steam production per hour) or approximately 7.5 BHP.
Higher temperature latent heat factors
0.0 PSI Gauge = 970.3 Btu’s 25.3 Lbs. Gauge = 933.7 Btu’s
5.3 PSI Gauge = 960.1 Btu’s 50.3 Lbs. Gauge = 911.6 Btu’s
10.3 PSI Gauge = 952.1 Btu’s 75.0 Lbs. Gauge = 940.5 Btu’s
15.3 PSI Gauge = 945.3 Btu’s 100.0 Lbs. Gauge = 888.8 Btu’s
Or – Divide the product of (gallons of water) x (pounds per gallons) x (temperature rise in ° F.) by 33,479 number of Btu’s in one boiler horse power to obtain boiler horse power = 7.5 from the example above.
Both of the above methods assume 100% efficiency. Add 25% to compensate for radiation heat loss, which is certain to occur. This will determine the minimum boiler horsepower required.
Note: One Btu will raise the temperature of one pound of water one ° F.
*Assumes sufficient heat exchange surface.