Hey, Physics whizzes...

Once again, I'm forced to bring a practical question to the SG boards, because no one I ask in real life has any clue. I know we have a bunch of science geniuses here, so I'm hoping someone will be able to help me.

It's 70 degrees outside, but 90+ in my apartment. It's a two-room unit on the second flood and the only way I can get any circulation is to open both the window and the door out to the hall, both in the kitchen (I can't open the windows in the other room because there's no screens and bugs will get in). If I have the door to the hallway closed, there's no breeze at all. There are stairs going down right outside my door, so I figure the difference in pressure or something is what draws the air in? But I really don't like leaving the door open because people can see/hear/WALK in and whatnot. I also have an overhead fan and a stand-up fan in the main room that I have on most of the time I'm home. (And no, I can't afford A/C.)

So my question is... I have a small table fan that I've been putting in the window, pointing in, but it actually seems to be more breezy when I have the fan off. Is the fan messing up the pressure... differential or something? Should I point it out the window to blow the hot air out, or should I not have it in the window at all?

Anyone have any solid ideas? I'm dying here, and no one ever wants to come over because it's so freaking hot.

Maybe get something like this so you can open the other window.

i bet you'd be able to get decent circulation if you put window fans in both rooms and kept all the doors between them open, just make sure one fan is blowing inward and the other one outward.

you'd probably be better off with an aspiring architect than a physicist. i know this because i am neither of those things.

Do you rent or own ? and how high and what shape are your ceilings ? by shape I mean are they peaked or flat and is there a loft of any sort, stuff like that.. and what is above them ? Roof , attic, another apt ? And the windows, what are the windows like ?

It sounds like what's happening now, is that the hot air from downstairs is moving up and coming in through your door, then you're trapping in the hot air by pointing the fan inward.

I'm no physics whiz (and would definitely defer to Vampirate who actually knows his stuff and can tell you the science behind it), but given the two things I know about heat (i.e. it rises, and increases with pressure), I think your best bet would be to seal your windows and doors, and attach a powerful exhaust fan to the window. This would A.) remove some of the hot air from the room, and B.) if the seal was tight enough, theoretically, lower the air pressure in the room, thus cooling it down some more.

Of course, you may want to crack open a window slightly from time to time for fresh air.

This is all just a guess. And I very well could be wrong.

Rent, which is one of the reasons why I never wanted to spend the money on buying my own screens. I asked the landlord if I could have some a few times but he keeps blowing me off.

The window fans may be a good idea, though... I'd forgotten they made those.

which way are your windows oriented? south, north? which direction do the prevailing winds go where you are?

btw, another thing you can do (depending on the humidity in your place) is buy/make a swamp cooler.

this is basically a fan blowing air through a chamber with water-soaked elements that are evaporating. since the evaporated air contains the cooler water vapor, the output sort of feels like an air conditioner (though not as effective). also, this generally works in low humidity environments.

google "swamp cooler", "evaporative cooler". or you can make your own like my friend did by buying a big tupperware container, hanging pieces of cloth inside, lengthwise, that soaked up water from the bottom, and a fan on one side blowing air in, escaping from an exhaust outlet on the other side.

Sounds like your place is in need of some venting in a crazy way. If you rent it's likely a mute point.
You want to get rid of the air as close to your ceiling as possible either by force or even just allowing it to escape. If you have access to the attic and it is well vented you may try just leaving that access open , with or without a fan. If you have a peaked ceiling a triangle opening 2-3 ft big will work really nicely in one or both ends. But ahhh, yeah. Maybe you can sneak up there with your sawzall when Mr. Landlord's not looking
Sorry.

Really, the only thing that's going to work for you is to move air through your apartment: in one end and out the other. Don't open the door to the stairway; that will only allow you to more readily exchange any cool air you might have with hot air coming up from below.

The thing that is going to do you the most good is to stick window fans in the two windows in your place that are farthest apart, with one pointing in and one pointing out. If the bugs are bugging you and your landlord sucks, buy your own tiny screen to duct tape to the outside of your inward-pointing window fan.

Other things that might help to a lesser extent:

The swamp cooler thing is a good idea. The easiest thing to do is just to drape a washcloth over the inward-pointing fan, and pour some water on it every once in a while (although the more elaborate one SuicidePuppies described would be more effective and require less attention). It takes about five times as much energy to evaporate a given amount of water as it does to raise it from just above freezing to boiling, so evaporative cooling is very effective. If you just can't fucking stand things anymore, lie on the floor with a soaked towel draped over you with your table fan pointed across the top for a while.

A turban fan is also an excellent way to vent hot air, but one that requires a hole cut in the roof. If the temperature is an ongoing problem in your apartment, you might talk to your landlord about letting you install one. If it makes the apartment attractive to future tenants, he might be cool with it.

I recommend getting two of those big boxy $15 fans at target or wherever and putting them in two far apart windows with one blowing in and one blowing out. Crossbreezes work wonders. The fan in your window blowing in with your hall door open is fighting that hot air trying to climb up your staircase. It would be more effective facing outwards.

So, kind of what everyone else said.

Have one fan as an intake and one as an exhaust. It works wonders.

more importantly, what's the airspeed of an unladen swallow?

African or European?

The humidity is important also.

If it is hot and dry, you could use an evaporative cooler (fan blows over evaporating water running over wicker cage).

If it is actually humid, then you need to move the air across you (to get the evaporating going), or get your abode to change temp. Your flat could be retaining the heat, especially if it is concrete or brick.

Houses in Australia are typically wooden with no insulation - this allows the house to adapt quickly to any cooling.

When I lived in Pakistan (only a couple of miles from the Red Mosque actually), the concrete house, floors, roof, walkways, would hold the heat all day and well into the night.

Don't be a tight arse, get some screens. You can velcro them on or use magnets

90F !! Thats only 32 C - call me when it gets above 120 F

I don't know that.

AAAAHHHHH!!!!

Also, don't forget the old trick of opening yr place up at night, and then closing it up tight before the sun starts pouring in. Trap the cool air inside, close all yr blinds to prevent a greenhouse effect, and, depending on how much it cools down at night, you could be set for the whole day.

Or buy an in-window air conditioner.

hot air rises, when you open a window and your door that has access to the stairs the natural flow will be this: The hot air in your apartment will want to escape out your windows, this will necessarily pull cooler air in through the door. Try blocking the door open just a bit so folks can't see in so easily and using the fan to blow out a window or better yet, in the door.

If it's particularly dry right now in wisconsin you could do a makeshift swamp cooler with a sheet or light towel, a bucket or pot of water & the fan. hang the towel so that the bottom is in the bucket of water (it will wick water up itself) then blow air on it with the fan. The evaporating effect will give a cool breeze. Something heavy on the towel in the bucket will let you put more fan to it without blowing it around. You must keep the air flowing through the room or it will just get humid and not work anymore. But if your air is at all humid don't bother, it won't do anything.

Wisconsin is actually humid as fuck during the summer. I'm like 4 blocks from Lake Michigan, which I guess keeps it a little cooler, but makes the already-bad humidity even worse.

However, I have been trying to keep the air circulating with the fans, and that seems to have good results. I got a Target gift card for my birthday and might invest in a window fan to point out the unscreened window and hope it blows away any curious bugs.

Thanks for the tips, everyone!