Calculation model for evaluating the influence of different spray desuperheating modes on the unit thermal economy was established by exhaust coefficient method.Taking an ultra supercritical 1 000 MW unit as the object

the unit thermal economy under different spray desuperheating modes was evaluated

with assumption that the spray desuperheating flow rate of main steam equaled to that of the reheat steam.The results showed that

for both superheater and reheater spray desuperheating system

the one shunted from the final heater outlet had smaller effect on the unit thermal economy than that from the water feed pump outlet;the spray desuperheating for reheater caused more unit thermal efficiency drop than that for superheater;for the same spray quantity

the unit thermal efficiency drop resulted from the reheater spray desuperheating system was about 10 times larger than that from the superheater spary desuperheating system;for the same spray desuperheating mode

the unit thermal efficiency drop was proportional to the spray quantity.