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Thread: How to determine the flow?
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02-02-2011, 05:53 PM #1
How to determine the flow?
Hello,
I am trying to design cooling system for an electronic heat load of the 2.5 kW in a chamber.
I need to supply air at 17 deg C to maintain the temperature of the air in the chamber at 20 deg C. (As per the specifications)
The chamber is insulated.
In this case how to determine the Air Flow?
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02-02-2011, 06:43 PM #2
Re: How to determine the flow?
We need a few more details, as usual.
Ambient air temperature
Size of room
Air Change Rate
etcBrian - Newton Abbot, Devon, UK
Retired March 2015
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03-02-2011, 10:35 AM #3
Re: How to determine the flow?
Thanks for the reply.
Ambient air temp is 45 deg C (max)
Size of the chamber is 520 mm (width) x 520 mm (Length) x 900 mm (Height)
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06-02-2011, 05:00 AM #4
Re: How to determine the flow?
Q=V*cp*ro*DT/3600
From that
V(air flow)=Q*3600/cp*DT*ro [m3/h]
cp heat capacity of air
ro density
DT-your case 3K
you allready have a Q=2.5kW so just change the units and that is it.
And also you can do it according to the desired air change rate.Be careful about reading health books. You may die of a misprint.
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08-02-2011, 10:32 PM #5
Re: How to determine the flow?
KW = air flow * delta T*specific heat of air *density of air*conversion constants
KW = L/s * ˚C * cal/gm˚C *gm/L* kw-hr/cal * s/hr
for air, cal/gm˚C = .25, density gm/L =1.25
s/hr = 3600, kw-hr/cal =1.163*10^-6
so L/s = KW/(˚C * cal/gm˚C *gm/L* kw-hr/cal * s/hr )
= 2.5/(3*.25*1.25*1.163*10^-6*3600)
= 640 L/s
This is the minimum air flow needed to absorb 2.5KW with a temperature rise of 3˚C. Any higher air flow will result in a chamber colder than 20˚C, ultimately approaching the 17˚C supply air temperature.Last edited by dougheret0; 08-02-2011 at 11:07 PM. Reason: clarify formula
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