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04-13-2009, 09:18 AM   #1
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## Heat transfer

I have a 4 in. duct moving air at 300 FPM. I know that this equals about 24 CFPM. I want to know how much energy(BTU's or watts) it takes to heat this air 10 degrees F. The air starts at 30 F, 50 Hum. and sea level.
+ or - 5% is good enough.
OR, how much energy does it take to heat X amount of air(CFPM), Y amount of degrees(F)?
Thanks,
Chuck

04-13-2009, 09:53 AM   #2

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1.08 BTUs per CFM per 1° temp rise.

In the case of your 4" duct, at 24 CFM and 10° rise, 259.2BTU.

A 4" rouind at 300 FPM is 26CFM.
(10*1.08)*26=280.8 BTUs.

04-13-2009, 11:34 AM   #3
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## Thanks

Quote:
 Originally Posted by beenthere 1.08 BTUs per CFM per 1° temp rise. In the case of your 4" duct, at 24 CFM and 10° rise, 259.2BTU. A 4" rouind at 300 FPM is 26CFM. (10*1.08)*26=280.8 BTUs.
Thanks Beenthere, follow-on question- the literature says that it takes one BTU to heat 1 CF of water 1 degree C. What am I missing?

 04-13-2009, 11:42 AM #4 Member   Join Date: Jul 2008 Location: NW of D.C. Posts: 5,990 Rewards Points: 2,000 xxxxxx! Last edited by Yoyizit; 04-13-2009 at 01:06 PM.
 04-13-2009, 12:30 PM #5 An old Tradesmen   Join Date: Oct 2008 Location: Somewhere Posts: 33,555 Rewards Points: 6,074 Its 1 BTU to heat 1 pound of water 1°F. A cubic foot of water, is 7.49 gallons, and weighs 62.39 pounds at 60°F.
04-13-2009, 12:36 PM   #6
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## Thanks again

Quote:
 Originally Posted by beenthere Its 1 BTU to heat 1 pound of water 1°F. A cubic foot of water, is 7.49 gallons, and weighs 62.39 pounds at 60°F.
Damm, you the man.
Thanks,
Chuck

04-13-2009, 12:46 PM   #7

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