Wednesday, August 06, 2008

Thermodynamics Is So Hot

Did you know that turning on your ceiling fan actually makes a room WARMER instead of cooler? Oh yes it does. Many people have argued with me about that, but I could never explain why it was true; I just knew I was hotter with the fan on than off (mostly because I don't like to sit directly under it). But I found the answer tonight on the Net, confirming that I've been right all along. (Because, you know, if it's written on the Net, it MUST be true, but in this case it really is. :D) I know it says it doesn't heat the room up by much, but if you think about it, one degree is the difference between boiling and not boiling too. I feel much the same way with the fan on.

God help me, but I love being right. Must be the combination of Irish and Scottish genes.

The physics of it goes: the electricity required to run the ceiling fan is converted directly to heat which is released into the room and will, therefore, raise the temp since simply moving the air around does not technically "chill" it.

The reason you feel cooler with the fan on is due to the wind chill effect increasing convective heat loss on your body; i.e., the breeze created by the moving air evaporates the sweat from your skin faster. Faster evaporation = cooler human.

Since moving to San Diego and acquiring two of these portable air conditioning things that look a whole lot like the girl robot in Wall-E, I've noticed that they don't do near as good of a job at cooling the place as my old window A/C units used to. I couldn't figure out why, until I applied the fan information to the air conditioning problem.

Both machines contain a compressor which is part of the cooling system. The compressor uses a lot of electricity (trust me - I about fainted right there at the mailbox when I opened my first power bill!) and all that electric is converted to heat the same as what a ceiling fan does.

In a window A/C, the compressor is hanging outside the window, thus the only thing INSIDE the room is the cool air streaming through the vent (or at least any heat coming from the unit is minimal).

With a portable A/C, the whole thing is inside the room - cool air flow AND compressor creating heat. So the way I see it, the machine is fighting itself and slurps up power faster than a Republican can abuse the environment. ACK.

Oh sure... most of these portable jobs have an exhaust pipe you have to put up to a window, which I suppose was some engineer's idea of solving the problem of expelling the heat from the compressor. Pfsssshh. They must've forgot to request that the tube itself be insulated against releasing heat back into the room, or more likely, it just wasn't in the budget.

So that, kids, is why I don't use my ceiling fans even tho I like having them because they look pretty (they actually come in handy in the winter if you're not sitting under one), and why my portable A/C units that cost twice as much as the window ones suck swamp water in comparison. At least now I know. It is also why I will make damn sure the next place I live has central heat and air. Shame, that. It's really the only flaw this condo has.


CSD Faux Finishing said...

I knew it! When we lived in NY we used to put the fan on blow in the winter but suck in the summer. Basically just reversing the way the blades rotated so it would create a "difference" in the air. I used to tell Matt I couldn't feel any difference but he insisted there was one. I am so sharing this with him tonight because, as an Irish gal myself, I too have the need to be right all the time :)

Hope you all stay as cool as possible out there! Where is that daughter of yours btw?

draagonfly said...

Daughter is still in NJ, trapped by the very car she begged and begged to have that I really didn't want to give her. Just another example of be careful what you wish for. At least now a fire has been lit under her butt because there are problems between the boyfriend and his family since she has overstayed her welcome. Hard life lessons for that one!

And I am so glad to be able to help you with ammunition to prove yourself right! That need is the affliction of our people. :D haha

CSD Faux Finishing said...


Came over to see if you had a new post up and your ads are for portable air conditioners. LOL