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# Boiler Horsepower

## 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)

where

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

 from multiply to 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

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Temperature

oC
oF

Length

m
km
in
ft
yards
miles
naut miles

Area

m2
km2
in2
ft2
miles2
acres

Volume

m3
liters
in3
ft3
us gal

Weight

kgf
N
lbf

Velocity

m/s
km/h
ft/min
ft/s
mph
knots

Pressure

Pa (N/m2)
bar
mm H2O
kg/cm2
psi
inches H2O

Flow

m3/s
m3/h
US gpm
cfm

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