The wind blown down by industrial ceiling fans is hot and cannot achieve cooling effect. Is this correct?

Some people say that the wind blown down by a 7-meter-3 fan is hot, is that right? Firstly, let's take a look at the motion diagram of the airflow after turning on the fan. The airflow is indeed a continuous supply of air from the roof to the ground. Common sense tells us that hot air has a low density and accumulates on the roof, which is why some people say that what comes down from a large fan is the hot air from the roof. But this statement is both correct and incorrect. Why? The fan is turned on, and the air from the roof is constantly being sent to the ground. Is the roof in a negative pressure state, and the air next to it will quickly replenish and flow to the roof, forming such a circulation of air flow. So what blows down is not always the air from the roof, but an air circulation.

簡單來說就是當(dāng)大風(fēng)扇轉(zhuǎn)動時，扇葉帶動氣流，氣流沿著扇葉角度向下移動，當(dāng)向下移動的氣流遇到地面后向外折射移動，這種向外折射移動的氣流稱為水平噴射，相對于風(fēng)扇的直徑，在持續(xù)源源不斷的氣流向外推下，形成一個大面積的圓柱形立體風(fēng)。當(dāng)持續(xù)噴射壓力流達(dá)到其潛力，它就會向外移動，直到遇到側(cè)壁或其他垂直表面，所以柱形立體風(fēng)往往大于風(fēng)扇直徑的數(shù)倍以上。這種立體移動氣流會破壞身體周圍的水分飽和邊界層，并加速蒸發(fā)，從而產(chǎn)生冷卻效果。