In energy transfer and conversion processes of a thermal system or equipments, the ratio between the
exergy used or gained and payment or consumptive exergy is defined as the exergy efficiency of the
system or equipments [2]. In order to express every equipment’s production purpose, many scholars use
“fuel-product” concept to define equipments function [3,4]. Quantified the production purpose of a
equipment or a component is “product” (P), and consumptive exergy for the “product” is called “fuel”
(F).Then, the exergy balance equation can be written as follows: