The applicability of the exhaust temperature correction calculation model in the Performance test code for utility boiler(GB/T 10184—2015) is investigated under conditions with atypical inlet air temperature and air preheater performance state. The improved calculation model is given and moreover

the test results on a 300 MW unit are checked by using the improved model. The results show that

when the air leakage rate at the flue gas side of the air preheater deviates from the design value by more than 1% and the inlet air temperature deviates from the design value by more than 20 ℃(the non-typical inlet air temperature condition)

the corrected calculation result of the exhaust temperature according to the GB/T 10184—2015 has relatively large error. The air leakage rate and the flue gas side efficiency should be introduced in the correction calculation. At different electricity loads

the air leakage rate at the flue gas side of the air preheater of the test unit is 2%～3% larger than the design value. According to the corrected calculation results of GB/T 10184—2015

the tG 15δA1 will be 1.7～2.6 ℃ lower. This error value is proportional to the flue gas side air leakage rate(AL). Under atypical boundary conditions(the inlet air temperature deviates from the design value by more than 20 ℃)

the air preheater flue gas side efficiency η is 1.2%～3.3% lower than the reference condition. According to the GB/T 10184—2015

the calculation result tG 15δA1 is 0～7.2 ℃ higher

this error value is positively correlated with the system inlet air temperature. The modified calculation model proposed in this paper not only eliminates the correction calculation error

but also provides scientific guidance for the accurate calculation of thermal efficiency of many utility boilers.