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A question on window breezes and bernoulli effect

  1. Jul 7, 2009 #1
    Hello there!
    It's been about a grillion degrees up here in my home town recently and last night this led me to a sort of conundrum. If I open the window in my room but leave my door shut, hardly any air comes it at all. If I open my door, there's a strong puff of wind that comes into the room and then a good steady flow continues. Just because of the components of this situation I always assumed that it had something to do with air pressure. Somehow opening the window decreased the air pressure in the room, sucking in cool air from the outside. But I realized that I can't really explain why the pressure would be less once you opened the door. Is my intuition just completely leading me astray? I've been thinking about this all night, somebody put me out of my misery!
  2. jcsd
  3. Jul 13, 2009 #2
    Your house is a big box of stratified hot air warmer than the out side air because of heat from lights, appliances etc. If your house is air tight an open widow will not let outside air into the house because there is no way for the air in the house to excape. However if you put a hole in the top of your house (gaps around windows, exhaust fans, plumbing penatrations etc.) the warm air in the house will excape and be replaced by relatively cooler outside air. The leaks around the top of the house creates what is called a "stack effect" similar to that of a chimney. The effect can be increased by increasing the temperature difference between inside and outside air, increasing the height of the house or wind driven affects. The fact that you have air entering a house tells you that air must be leaving somewhere else. The air movement will be caused by pressure differences created by the stack effect.
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