Fans

As hot weather arrives, people start to tell of sleepless nights spent surrounded by fans. The fans may be more of a problem than a solution.

Fans consume electrical energy and release it as heat, partly in the mechanism of the fan, and partly in motion of the air. The stream of air generated by a fan quickly dissipates into eddies and soon fades away into random motion of individual molecules, what we usually call 'heat' So a fan is likely to make the room as a whole warmer.

Sometimes parts of a room may be cooled. If one part of a room is cooler than another a fan could be set to move air from the cooler part of the room to the warmer thus changing the distribution of heat but the cooling effects of a fan usually depends on evaporating water, so a fan blowing air over a moist sweaty body may cool that body. That will only take place while the sweaty body exposes itself  to the output of the fan. Sometimes sweaty bodies leave fans switched in their absence, expecting the room to be cooler when they return. They are likely to be disappointed.