What is boiler efficiency? What is thermal efficiency of an steam engine?
Boiler efficiency is the ratio, often expressed as a percentage: (heat energy out)/(heat energy in) of the boiler. The difference between the two arises mainly from the heat escaping up the chimney stack, although there's also loss due to radiation and convection from the boiler surfaces. In the case of a steam engine the thermal efficiency is the ratio (mechanical energy out)/(heat energy in). A large portion of the difference between the two arises from thermodynamic considerations which do not affect a boiler since it performs no energy conversion.
