What is the meaning of this 1 BTUlb-f?

Answer 1

The notation "1 BTU/lb-f" refers to one British Thermal Unit (BTU) of energy per pound-force (lb-f). It is a measure of energy, specifically the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit. The "lb-f" indicates the force due to gravity acting on that pound mass, often used in contexts involving thermodynamics or heat transfer where the weight of the material is relevant.