Exergy Analysis of Boiler Based on the Temperature Gradient

In this paper, three temperature degrees are divided in boiler according to the character of transfer and combustion in the boiler. At the same time, three units are divided on the basis of temperature gradient. The energy and exergy analysis are on these basis. Energy and exergy efficiency are deduced according to the energy and exergy equations of three units as shown in fig.1. In this study, we take the temperature of hot air at the air pre-heater for example. When the temperature increases, the adiabatic flame temperature also increases, resulting in the exergy loss of the first unit decreases. However, with the increase of the adiabatic flame temperature, the exergy loss of the second and third units will increase if the exergy of the working fluid is invariable. General considerations, the total exergy loss will be increased; exergy efficiency will be reduced.