higher humidity better cooling???

slavik · 10-16-2004, 12:38 PM

since water has a high capacity for energy storage, does it make sense that in aircooling, the room having higher humidity (30% vs 80% at same temperature) would give you lower temperatures on the CPU while aircooling it ...

does it make sense?

bigben2k · 10-16-2004, 01:24 PM

It does. We examined this some time ago, and concluded that the difference would not be measurable.

slavik · 10-16-2004, 10:29 PM

because of the low amount of water?

redleader · 10-17-2004, 12:13 AM

There are tables of heat capacity of air at various humidities. You could look it up and see for yourself what difference it makes.

IIRC, humidity is taken into consideration when sizeing condensors and radiators on large commercial and industrial loads.

Les · 10-17-2004, 02:17 AM

Quote:

Originally Posted by redleader

There are tables of heat capacity of air at various humidities. You could look it up and see for yourself what difference it makes.

.

Any link?
Have toyed with investigating but have found no data.

redleader · 10-17-2004, 03:39 AM

I saw them in an HVAC text from the 60s I dug out of a university library last year. Sorry I couldn't even tell you the title.

It never occured to me that they were hard to find (and it didn't interest me since we're at near zero humidity here in Arizona 300+ days a year)

lolito_fr · 10-17-2004, 04:18 AM

Rough formula for calculating moisture content of air (works for me):
%RH*4.1561*EXP(0.0619*T)
T is dry bulb air temp in °C
result is in grams of water per m3

The rest should be plain sailing

edit: IIRC, this is useable (ie <10% error) between 0 and 30°C

edit2: pretty good stuff here- http://www.coolit.co.za/psychart/chapter1.htm
(I think the Magnus formula is more trustworthy than mine...)

Les · 10-17-2004, 06:21 AM

Ta "lolito fr"
Think I could have looked harder.
Will have a play(honour bound) and report anything interesting

redleader · 10-17-2004, 04:35 PM

I looked up a few books today, and while I couldn't find any tables, I did find values for 0 and 100% humidity. You could probably use excel to plot the rest of the data points; its almost certainly linear, or at least very close to it.

0% = .24 (BTU/ft^3)
100% = .86

(at 70F and 1 Bar as I recall)

So its actually pretty significant.

greenman100 · 10-17-2004, 05:00 PM

Quote:

Originally Posted by redleader

I looked up a few books today, and while I couldn't find any tables, I did find values for 0 and 100% humidity. You could probably use excel to plot the rest of the data points; its almost certainly linear, or at least very close to it.

0% = .24 (BTU/ft^3)
100% = .86

(at 70F and 1 Bar as I recall)

So its actually pretty significant.

you think so?

the most the average person would be confortable in is 55%-75%

so like ,124BTU/ft^3 difference

Les · 10-18-2004, 05:21 PM

Using Air3.1 get :-

A total effect on "C/Wradiator" of less than 4% with 25c ambient ( ~ 17% at 50c ambient)

Edit - pasting data into Excel 97 produced arithmetic errors.
Have corrected

Les · 10-18-2004, 06:25 PM

Corrected arithmetic errors in previous post

10-16-2004, 12:38 PM	#1
slavik Cooling Neophyte Join Date: Jun 2004 Location: Brooklyn, NY Posts: 28	higher humidity better cooling??? since water has a high capacity for energy storage, does it make sense that in aircooling, the room having higher humidity (30% vs 80% at same temperature) would give you lower temperatures on the CPU while aircooling it ... does it make sense?

10-16-2004, 01:24 PM	#2
bigben2k Responsible for 2% of all the posts here. Join Date: May 2002 Location: Texas, U.S.A. Posts: 8,302	It does. We examined this some time ago, and concluded that the difference would not be measurable. __________________ WBTA (Water Block Testing Alliance) Nordic Hardware WC 101

10-17-2004, 04:18 AM	#7
lolito_fr Cooling Savant Join Date: Dec 2003 Location: France Posts: 291	Rough formula for calculating moisture content of air (works for me): %RH4.1561EXP(0.0619T) T is dry bulb air temp in °C result is in grams of water per m3 The rest should be plain sailing edit: IIRC, this is useable (ie <10% error) between 0 and 30°C edit2: pretty good stuff here- http://www.coolit.co.za/psychart/chapter1.htm (I think the Magnus formula is more trustworthy than mine...) Last edited by lolito_fr; 10-17-2004 at 04:46 AM.*

10-18-2004, 05:21 PM	#11
Les Cooling Savant Join Date: Oct 2001 Location: Wigan UK Posts: 929	Using Air3.1 get :- A total effect on "C/Wradiator" of less than 4% with 25c ambient ( ~ 17% at 50c ambient) Edit - pasting data into Excel 97 produced arithmetic errors. Have corrected Last edited by Les; 10-18-2004 at 06:22 PM.

10-16-2004, 10:29 PM	#3
slavik Cooling Neophyte Join Date: Jun 2004 Location: Brooklyn, NY Posts: 28	because of the low amount of water?

10-17-2004, 12:13 AM	#4
redleader Thermophile Join Date: Jun 2001 Location: The deserts of Tucson, Az Posts: 1,264	There are tables of heat capacity of air at various humidities. You could look it up and see for yourself what difference it makes. IIRC, humidity is taken into consideration when sizeing condensors and radiators on large commercial and industrial loads.

10-17-2004, 03:39 AM	#6
redleader Thermophile Join Date: Jun 2001 Location: The deserts of Tucson, Az Posts: 1,264	I saw them in an HVAC text from the 60s I dug out of a university library last year. Sorry I couldn't even tell you the title. It never occured to me that they were hard to find (and it didn't interest me since we're at near zero humidity here in Arizona 300+ days a year)

10-17-2004, 06:21 AM	#8
Les Cooling Savant Join Date: Oct 2001 Location: Wigan UK Posts: 929	Ta "lolito fr" Think I could have looked harder. Will have a play(honour bound) and report anything interesting

10-17-2004, 04:35 PM	#9
redleader Thermophile Join Date: Jun 2001 Location: The deserts of Tucson, Az Posts: 1,264	I looked up a few books today, and while I couldn't find any tables, I did find values for 0 and 100% humidity. You could probably use excel to plot the rest of the data points; its almost certainly linear, or at least very close to it. 0% = .24 (BTU/ft^3) 100% = .86 (at 70F and 1 Bar as I recall) So its actually pretty significant.

10-18-2004, 06:25 PM	#12
Les Cooling Savant Join Date: Oct 2001 Location: Wigan UK Posts: 929	Corrected arithmetic errors in previous post

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