Final answer:
Convection results in faster cooling in gases compared to liquids because gases are less dense and can move more freely, allowing for more efficient heat transfer. Using a fan enhances this effect by constantly replenishing the warm air near your body with cooler air. Moreover, convection aids in evaporative cooling, like sweating, by preventing air saturation with moisture and promoting continuous heat loss.
Step-by-step explanation:
Cooling in a gas by convection is indeed typically faster than cooling in a liquid of the same temperature. Convection is the heat transfer due to the bulk movement of molecules within fluids (gas and liquids), where the warmer part of the fluid rises and the cooler part sinks, creating a cycle of heat transfer. In the case of gases, this process is generally more efficient due to the lower density of gases compared to liquids, resulting in faster heat transfer and thus more rapid cooling.
Using a fan enhances convection by increasing the flow of air. This means the warm air near your body gets replaced more quickly with cooler air from elsewhere, speeding up the cooling process. Additionally, since the density of a gas decreases with temperature, the hot air rises more swiftly, causing the cooler air to come in and replace it efficiently. This fluid motion contributes to a more pronounced cooling effect compared to still air.
Convection can combine with evaporative cooling, as seen when sweating cools the body. The phase change of sweat evaporating from the skin absorbs a significant amount of heat, but without air flow from convection, this process would cease as soon as the air gets saturated with moisture. The movement of air ensures continuous evaporation and thus a continuous cooling effect.