system
Given the following post, respond as if you're commenting on Reddit:
human
Why are cooling towers shaped the way they are?

Power plants or large factorys all have the same shape of their cooling tower. The radius is smaller in the middle and widing up on top again. Whats the reason we dont use the same radius everywhere or it only gets smaller higher up.
gpt
The broad base is to support the structure, as you go up, the radius gets smaller to allow for a faster flow of vapour out of the tower (warm vapour will tend to go upwards and by reducing the area, you force it to go faster). On the top of the tower, you have the mixing between the vapour and the cold outside air. You would want this mixing to be as best as possible so increasing the radius a bit helps with this.