what ways do ceiling fans help you cool down?

Question

project in school

Answer 1

It moves the air and promotes the drying of your perspiration which make you feel colder.

Answer 2

First, you want to realize that with the exception of possibly affecting your thermostat by moving warmer air past it, any fan in a closed space will actually gradually warm the air by adding the work energy of the fan to the air. The oddest way a ceiling fan helps you is by moving (thereby mixing) the room's air. Everyone's heard "hot air rises" (actually, the heavier, cool air falls, pushing the hot air out of the way - go gravity!). The air around thermostat will usually be slightly cooler than around your head or the ceiling. Mixing the warmer air with the cooler air will raise the temperature of the air near the thermostat and may allow your HVAC to turn off and stop adding heat to the room. The biggest effect you feel though is the greater loss of heat from your body (cooling you) to the much larger body of air flowing over you that even a slow ceiling fan will cause. Almost stagnant air near your body warms as you lose heat causing that heat loss to decline and you to feel warmer. By forcing air to circulate, you not only keep the temperature difference about the same or greater (if the air by your feet, say, is markedly cooler), but you raise the heat loss by presenting moving air so the body of air into which you lose the heat greatly increases and so does the heat lost. This is why standing in front of a fan (which actually WARMS the air blowing through it!) feels so cooling. Another, small, way in which circulation helps is that no one to speak of has an insulated floor but most do have insulated walls and ceilings so the air around your feet is usually losing heat faster than the air by the ceiling (I am thinking of winter now... because it IS winter now, more or less...) and you take advantage of that. But modern ceiling fans do not do what their slow-moving ancestors did and which gave one pretty good control of the cooling effect: work with transom windows. Why? Because no one has transom windows anymore. (They are those little windows you saw above doors before they became a designer statement (unable to open) and then became gone altogether.) By choosing which transoms to open and which to leave shut, one could control the places the circulating air went to and pull nice, cool basement air, for instance, into the room you occupy and send that room's air through the basement to cool. Now we have only the HVAC's ductwork and returns to work with so fans today are higher speed to move much more air and really only help in the room and perhaps one next to it. Another small effect available is for a kitchen ceiling fan: by running it, you raise the pressure a little in the kitchen so the kitchen's exhaust fan, assuming you are running it, is able to draw slightly better and exhaust more of the (presumably) hotter, moisture-laden air from the cooking area limiting its effects on the rest of the room. There are physiological effects that differ from person to person as well as some minor effects that take place only in the beginning of use period. Some people's bodies begin to conserve heat when presented with a new, or sudden, temperature change producing a feeling of coolness regardless of actual facts. Some people feel cooler with just their heads being cooled rather than needing the whole body cooled. Some people go the opposite way where a ceiling fan is concerned as their foot temperature controls that feeling. All these will be most pronounced at beginning of use. All are certainly very debatable, not least because we are now talking about the feeling of coolness (not to be sneered at) rather than actual coolness. An example of a pretty minor physical effect that would slowly reduce due to mixing is that cool air (which holds less moisture than warm air) replaces warm air and the moisture (though there is less of it) has a greater temperature difference with your skin than the warm air moisture did causing the cool air/moisture mixture to be even more effective at cooling (because water transfers about nine (9) times as much heat from your skin as air itself does). This will decline as the air mixes and is not a huge effect anyway. It does introduce another worthy effect: evaporative cooling. Evaporating water takes all the energy it stored up from you. This is the idea behind the misting areas one sees at sporting events, concerts, etc. Very effective. With moving air the amount of evaporative cooling rises greatly compared to stagnant air. (This is why you should not wipe away sweat when wishing to cool down unless it is running on you (rather than sitting quietly, absorbing heat and waiting its chance to evaporate) or you have an important secondary concern such as liking dry clothing. Continually towelling dry after a hot shower is particularly counter-effective - unless a pesky secondary concern such as time ticking away requires you to do it.) In some circumstances, but not usually, this effect can be more important than the effect from the movement of air allowing greater heat transfer or the mixing of air. Finally, ceiling fans can be very effective if there is a source of artificially cooled air such as a room with large windowed areas away from where you happen to be or you open a door or window to the outside and want that to work faster.