In winter

spring

and autum seasons at norther area in China

the natural draft counter flow cooling towers were generally adopting an operation mode with water tricking in the outer area of the cooling tower

while in a part of the centre area

there isn't water tricking.In this case

however

the traditional calculation method of thermal performance will be unsuitable to use.Through simplified assumption that the density of hot air is changing linearly with the height of tower

and the resistance of rain droplets is even with the their radiuses

an one-dimensional calculation method for thermal performance of cooling towers with water destribution in the outer area has been deduced and obtained.After comparison with the prototype measured data

the calculation error isn't greater than 3 ℃

tallying well with the measured data

providing reference for the cooling tower design.