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Revision C
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RUN
TIME
CALCULATIONS
The following calculation can be used to estimate the amount of run time an APD-D series dehydrator will
take to pressurize a given volume. This calculation is a simplified best-fit estimate. Actual pump times
will be dependent on many variables, such as:
APD-D flow variations. Each dehydrator has flow variations. The specifications indicate the
minimum flow for each model.
APD-D service condition. How old the unit is, how well maintained.
APD-D environmental conditions. The environment in which the dehydrator is operating
has an effect on its performance.
System flow restrictions. Any restrictions in the distribution system which the dehydrator
is pressurizing can have pronounced performance consequences.
System air tightness. Any leaks in the distribution system which the dehydrator is
pressurizing can have pronounced performance consequences.
And other variables…
=
−
.
=
−
+
−
= Total system run time in minutes
= Volume of system in m
3
, ft
3
, gallons, or liters
= Volume conversion factor to cubic feet
= 35.314 for Volume in cubic meters (m
3
)
= 1.0 for Volume in cubic feet (ft
3
)
= 0.1337 for Volume in gallons
= 0.0353 for Volume in liters
= Lower operational pressure, psig (where
compressor starts)
= Upper operational pressure, psig (where
compressor stops)
= Effective flow (linearized average)
= Dehydrator output flow, CFM (cubic feet per
minute @ MSL, 0 psig, 23° Celsius, 50%RH)
= 0.22 for APD20-D
= 0.19 for APD22-D
= 1.0 for APD70-D
= 0.85 for APD72-D
= Flow correction factor for pressures above
0 psig
= 0.91 for APD20-D, APD22-D, APD72-D
= 0.92 for APD70-D
= Elevation AMSL (above mean sea level) in
feet
= Elevation correction factor for flow
= 0.000024 for APD20-D
= 0.000022 for APD22-D
= 0.000070 for APD70-D
= 0.000060 for APD72-D
= Pressure correction factor for elevation
= 0.94
Excel
Formulas:
Assume APD20-D with
33 meters of E65 elliptical
waveguide.
calculated in cell A10:
=((A5*A6^A4-A7*A8*A9^A4)+(A5*A6^A3-A7*A8*A9^A3))/2
calculated in cell A11 in fractional minutes:
=A2*A1*((A4-A3)/14.696)/A10
calculated in cell A12 in [h:mm:ss] format.
=INT(A11/60)&":"&TEXT(INT(MOD(A11,60)),"00")&":"&TEXT(
INT(MOD(A11*60,60)),"00")
