-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 1 KWH = 3.6 Million joules (i.e. 1 watt = 1 joule/sec)
Specific heat of air at ~room temp @ 1 ATM ~ 720 J/Kg/oK Density of air at ~room temp @ 1ATM ~ 1.2 Kg/m3 1 foot = 0.3048 m So how big is the room ? Assuming say 20x20x12 ft = 136 m3 = 165 Kg Let's say the room is drawing a total of 10 amps, so 1200 watts or 4.32 M joules per hour. If there were no ventilation or other dissipation of heat, in one hour the room would be expected to go up 36oC (.01oC/sec) ! Ordinary industrial ventilation should have a minimum of 10 air exchanges per hour. However, it's not as though the air is really replaced 10x though, rather the rate of exchange is 10/3600 volume per second, and the amount of unreplaced air remaining is (1-exchange fraction)^t. On this basis about 1/2 the air is removed every 5 minutes so, instead of going up 3oC in 5 minutes, it would go up more like 1.5oC in 5 minutes, or a guesstimate would be 4-18oC/Hr. dT/dt=(c-1/18)- T(t)/360 (or something like that) ~ln(360*.045555*t) ~11oC (~20oF) in an hour The other way to look at it is you need ventilation+cooling to equal the energy going into the room. For 4.32 million joules you need about 4100 BTU of cooling. We have freezer & equipment rooms that need up to 18000 BTU & special ventilation ducts for individual pieces of equipment in the lab. David Looney Tracy R Reed wrote: > At work last month we had half of our servers go down because a power > strip which was supposed to have blown its breaks at 15 amps blew it at > half that. At home my computer room is already getting quite warm and it > is barely summer. The computer room has always been the hottest part of > the house yet I need it to be the most comfortable because that is where > I spend most of my time and need to be able to think. So this has me > thinking about a few things... > > Can anyone recommend a simple device which can measure the amperage > used? Preferably without having to place it inline (I think some can > measure the EMF) but inline is doable if that is all there is. > > Let's say a computer draws 1 amp. What is the rule on how much heat this > adds to a room? Any way to calculate how many degrees it might raise the > temperature of the room? I think we can assume that pretty much all of > that 2 amps turns into heat. I know power for electricity is voltage > times current so that would be 110 volts times 1 amp which is 110 watts. > A watt is 1 joule of energy per second. So at 110 watts I am dumping 110 > joules of energy per second into the room. If I run the computer for an > hour I have added 396000 joules of energy to the room. If the room is > 10x10x8 and we assume no outside circulation how fast will the room heat > up? The goal being to see if that it is reasonable that the computer is > making this room noticeably warmer (say, 5 degrees or more warmer) than > it would be without the computer. > > Does anyone think it would accomplish much to somehow vent the hot air > coming out of my computer to the outdoors instead of into my room? It > just struck me that it must be more efficient to vent the hot air > outdoors and cool the ambient air than to try to cool the hot air from > the computer. I am surprised more datacenters are not trying to do this. > And if it does make sense to do this (I strongly suspect that it does) > has anyone seen kits or cases for this? I think I might go down to the > hardware store tomorrow and buy some of that flexible plastic dryer vent > hose to attach to the computer and then hang out the window. But how to > attach it to the back of the case? Hmm...just had an idea: I could get > one of those metal fittings that go on the inside of the wall that the > dryer hose attaches to, drill four holes in it, and put the bolts that > hold the fan in place through it and then through the case and the fan. > Yep, a run to the hardware store is definitely in order. I'll let you > know how it goes. > -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.2 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iD8DBQFEgxidb357MXAYfs8RApZxAJ0a3EK9AmVnyLNQqR2MgoXJGCR5iwCfcZYX pSn8NZnvWC4RZRPR/fUCl2Q= =LmXe -----END PGP SIGNATURE----- -- [email protected] http://www.kernel-panic.org/cgi-bin/mailman/listinfo/kplug-list
