by Guest » Fri Apr 15, 2005 9:40 pm
The BTU is imprecisely defined because the properties of water change depending on the temperature range over which the properties are measured. It is the heat to heat 1 lb of H2O 1 degree F, but temperature of the water matters, and there are about 10 "flavors" of BTU which differ in 4th significant figure and beyond.
However, 1 IT "steam table" BTU = 1.055056 kJ.
Measured under other conditions, values range from 1.05435 kJ to 1.05967 kJ.
(Similar problems exist with the calorie and Calorie)