Entropy

Entropy is the heat available measured in Btu per pound degree change for a substance.

Entropy calculations are made from generally accepted temperature bases. For heating and steam power using water as the medium, the accepted base is 32 F. For domestic, and most commercial refriger­ation calculations, the base is -40 F. For research and very low-temperature work, a base of a lower temperature may be selected. Entropy is generally used only in engineering calculations. Entropy tables have been worked out and are contained in most engineering handbooks.