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

                                                  970

 

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.