Heat transfer area and boiler horsepower
Boiler horsepower - a power unit from the 19th-20th centuries - was used to rate the capacity of a boiler to deliver steam to steam engines.
A common definition of one boiler horsepower is the amount of energy required to produce 34.5 pounds (15.65 kg) of steam per hour at pressure and temperature 0 psig (0 bar) and 212oF (100oC) - with feed water at pressure 0 psig and temperature 212oF. One boiler horsepower is about 33479 Btu per hour (about 9812 watts, 8437 kcal/hr).
Boiler horsepower was used in USA, Australia, and New Zealand and have been calculated in different ways.
PBoHP = A / k (1)
PBoHP = boiler horsepower
A = heat transfer area (ft2)
k = standard area (ft2) - in New Zealand it was common to use 17, in US it was common to use 10 before year 1900 - and more common to use 5 after
Be aware that the a boiler horsepower is not the commonly accepted 550 ft lbf/s and the generally accepted conversion factor of 746 Watts = 1 horsepower does not apply.
Boiler Conversion Ratios
|sq.ft. EDR steam||240||Btu per hr.|
|sq. ft. EDR water||160||Btu per hr.|
|Boiler hp||33.5||MBtu per hr.|
|Boiler hp||140||sq.ft. EDR steam|
|Boiler hp||223||sq.ft. EDR steam|
|Boiler hp.||34.5||lb. per hr. steam|
|lb. per hr. steam||970||Btu per hr.|
|to||divide by above||from|