Heat Loss from a Closed Tank
Heat Loss from a Closed Tank
(OP)
I have a large fire protection tank, 34ft tall x 29ft dia, holds 175000 gallons of water. I have a Lowest One Day Mean Temp of 25F and the min target temp is 42F. Tank is made of carbon steel.
Using the NFPA 22 figure 16.1.4, heat loss = square area x (heat difference) / R, I get a heat loss of 8,164kW, or 24 million BTU/hr.
Assumed: R=0.0031 ft2 F hr/BTU, A=4400 ft2, deltaT = 17
However using Q=hA(deltaT), I get a heat transfer rate of 12.4kW or 42308 BTU/hr
Assumed: h = 3.231 W/m2 K, deltaT = 9.44 K, A = 408m2
These are wildly different results and I can not seem to find the reason.
Thanks in advanced.
Using the NFPA 22 figure 16.1.4, heat loss = square area x (heat difference) / R, I get a heat loss of 8,164kW, or 24 million BTU/hr.
Assumed: R=0.0031 ft2 F hr/BTU, A=4400 ft2, deltaT = 17
However using Q=hA(deltaT), I get a heat transfer rate of 12.4kW or 42308 BTU/hr
Assumed: h = 3.231 W/m2 K, deltaT = 9.44 K, A = 408m2
These are wildly different results and I can not seem to find the reason.
Thanks in advanced.
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RE: Heat Loss from a Closed Tank
4400 x 17 / 1.757 = 42,562 BTU/hr.
Conversion error?
Good Luck,
Latexman
RE: Heat Loss from a Closed Tank
RE: Heat Loss from a Closed Tank
Your R, inverted, comes out to 1831.6979 W/m^2-K, so a factor of ~600 larger than your h; this magnitude is more for convection in a water-cooled application.
TTFN (ta ta for now)
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