After putting direct air-cooled unit into operation for some time

the influence of thermal resistance due to internal and external fouling of radiators'tubebandle in the air-cooled condenser upon the thermal economic efficiency of unit is remarkable.Taking 600 MW direct air-cooled unit as an example

and supposing the thermal resistance due to fouling in and out tubebandles of the radiators varying in a range of 0~0.001(m2·k)W

a mathematical model for calculating thermal resistance characteristics of fouling occurred in and out tubebandles used for the radiators of direct air-cooled unit has been established by using the η-NUT method

and corresponding characteristic curves being drawn out by programmed calculation

the influence of thermal resistance due to fouling occurred on tubebandles of air-cooled condenser

as well as wind velocity and ambient temperature on the windward side of air-cooled condensor upon the exhaust steam pressure being analysed.