I decided I would suffer today for the good of the community and made a
spreadsheet comparing Pressure Drops with Different Coolants. I have attached
the spreadsheet so that you guys can play around with it. All values are locked
except the ones highlighted. Unprotect the other values if you want, but do not
blame me if you mess it up.
Note that Diameter, Flow rate and pipe roughness all have and effete on
pressure drop and it is NON Linear. This means % change from 50/50 is different
for different configurations.
I guessed at some approximate values for
D, Vd and e. Also the density values in my text book
for water conflicted with those given by Evans. I went with the Evans values
but I do not trust them.
This sheet models a strait tube of
constant diameter with turbulent fluid flow.
With some time investment this could be
made to more accurately model an aircraft cooling system (multiple diameters,
fittings, bends, ect) but this gives a good ball park
figure of pressure drop differences. To take it another step we could do some
of the thermal calculations to. But this is all I am doing for now.
I would greatly appreciate it if someone
with knowledge of fluids could check my work.
Disclaimer: These are only model estimates
and have some associated error.
Alex Madsen
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Comparison of Pressure Drops with Different Coolants
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equation
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Water
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50/50
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NPG+
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Temp (C)
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212
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212
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212
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D Pipe Diameter (ft)
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0.167
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u dynamic viscosity (lbm/ft*s)
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0.0001882
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0.0004704
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0.0015455
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Flow Rate (GPM)
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30.00
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p density (lbm/ft^3)
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61.8
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64.9
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65
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Vd Flow Rate (ft^3/s)
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0.06684
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v kinematic viscosity (ft^s/s)
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u/p
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3.05E-06
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7.25E-06
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2.38E-05
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V velocity (ft/s)
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3.065
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L Pipe Length (ft)
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1.000
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RE Reynolds Number
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V*D/v
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167,759.41
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70,484.79
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21,486.34
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f Approximate turbulent friction factor
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((-1.8*LOG10(6.9/Re+((e/D)/3.7)^1.1))^(-1))^2
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0.0174
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0.0200
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0.0257
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e Pipe Roughness (ft)
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0.0000330
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delta P change in pressure (lb/ft^2)
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f*L*p*V^2/(D*2)
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30.28
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36.59
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47.04
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delta P change in pressure (PSI)
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0.210
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0.254
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0.327
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% change from 50/50
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-17.23
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0.00
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28.59
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