How is the evaporation of 34.5 pounds of water per hour at a feedwater temperature of 212°F defined?

The evaporation of 34.5 pounds of water per hour at a feedwater temperature of 212°F is defined as 1 BHP (Boiler Horsepower). The term "BHP" is a unit of power that is commonly used in the context of boilers and steam engines. Specifically, 1 BHP is defined as the ability to evaporate 34.5 pounds of water per hour into steam at a feedwater temperature of 212°F.

Understanding this definition is crucial because it directly links the amount of water evaporated to the power output of the boiler. In practical terms, if you have a boiler that can evaporate exactly 34.5 pounds of water in one hour, it is operating at a rate of 1 Boiler Horsepower. This makes it a standard measure for comparing the capacities of different boilers and their efficiencies.

In this case, knowing that the feedwater temperature is at the boiling point of water (212°F) indicates the conditions under which this evaluation is made, reinforcing the defined rate of evaporation as a standard measure of performance. Therefore, the answer is accurately 1 BHP, reflecting this specific relationship between evaporation rate and horsepower.