In a sealed room, a fan does not actually make the air cooler in terms of reducing its temperature. Instead, the sensation of coolness is primarily due to the movement of air. When the fan blows air, it creates a wind chill effect, which makes us feel cooler.
The perception of temperature is influenced by various factors, including the rate of heat transfer between our bodies and the surrounding environment. When we feel hot, our bodies release heat through a process called convection. The air surrounding our skin becomes slightly warmer as it absorbs this heat, creating a thin layer of warm air.
When a fan is turned on, it circulates the air in the room and blows this layer of warm air away from our bodies. As a result, fresh, cooler air comes into contact with our skin, allowing our bodies to transfer heat more efficiently. The increased rate of heat transfer gives us a sensation of feeling cooler, even though the actual temperature of the blown air remains the same.
It's important to note that fans are effective at providing comfort only when the air temperature in the room is lower than our body temperature. In extremely hot environments, where the air temperature is higher than our body temperature, using a fan may not be sufficient to provide relief, and additional cooling methods like air conditioning or evaporative coolers might be required.