Ceiling fan
A ceiling fan is a mechanical fan mounted on the ceiling of a room or space, usually electrically powered, suspended from the ceiling of a room, that uses hub-mounted rotating blades to circulate air. Ceiling fans typically rotate more slowly than other types of circulating fans, such as electric desk fans. They cool people effectively by introducing slow movement into the otherwise still, hot air of a room. Fans never actually cool air, unlike air-conditioning equipment, they in fact heat the air due to the waste heat from the motor and friction, but use significantly less power (cooling air is thermodynamically expensive). Conversely, a ceiling fan can also be used to reduce the stratification of warm air in a room by forcing it down to affect both occupants' sensations and thermostat readings, thereby improving climate control energy efficiency.
Fan (machine)
In 1998, Walter K. Boyd invented the HVLS ceiling fan. A lifelong inventor, Boyd was charged with developing a system to cool dairy cattle. Dairy cattle, when overheated, decrease milk production. Using the laws of physics and airflow, Boyd developed a slow moving fan that incorporated 10 aluminum blades and was 8-feet diameter. Unlike traditional ceiling fans that move quickly, this large fan moved slowly. Due to its diameter size, the fan moved a large column of air down and out 360 degrees and continuously mixed fresh air with the stale air inside the barn. They are used in many industrial and agricultural settings, because of their energy efficiency. It also cooled the inside of the barn without causing the dairy cattle undue stress or kicking up dust.