Pressure Loss Calculations
Pressure Loss Calculations
(OP)
Hello,
I am trying to calculate the major pressure loss in my system, and I just want to make sure I've done the calculations right.
I'm not sure I'm getting entirely accurate numbers.
Just so you know, the piping is circular, and the fluid being pumped is 15W40 engine oil... the density and viscosity are based off of physical measurements of 15W40 taken in the lab.
Anyway, here are my calculations:
Givens:
½" Piping Dh=0.0127 m
10 ft of tubing = 3.048 m
Max Flow Rate (21 L/min)
Viscosity at 20°C is ν = 357.38 cSt = 0.00035738 m^2/sec
Density = 818 kg/m^3
Pipe Area= π(0.25)^2= 0.19635 in^2
Volumetric Flow Rate=21 L/min =1281.5 in^3/min =21.36 in^3/sec
Flow Velocity=(Volumetric Flow Rate)/Area= 21.36/0.19635
=108.78 in/sec = 2.763 m/sec
Reynold's Number= (V* D_h)/ν =
((2.763)(0.0127))/0.00035738 = 98.187 (Laminar)
λ= 64/Re = 64/98.187 = 0.6518
Pressure Loss= λ(L/D_h )((ρ*V^2)/2)=0.6518(3.048/0.0127)[((818) 〖(2.763)〗^2)/2]= 488,439.4 Pa
I think this looks a little high, is all this correct, or did I botch it up somewhere?
Thanks,
Superfly
I am trying to calculate the major pressure loss in my system, and I just want to make sure I've done the calculations right.
I'm not sure I'm getting entirely accurate numbers.
Just so you know, the piping is circular, and the fluid being pumped is 15W40 engine oil... the density and viscosity are based off of physical measurements of 15W40 taken in the lab.
Anyway, here are my calculations:
Givens:
½" Piping Dh=0.0127 m
10 ft of tubing = 3.048 m
Max Flow Rate (21 L/min)
Viscosity at 20°C is ν = 357.38 cSt = 0.00035738 m^2/sec
Density = 818 kg/m^3
Pipe Area= π(0.25)^2= 0.19635 in^2
Volumetric Flow Rate=21 L/min =1281.5 in^3/min =21.36 in^3/sec
Flow Velocity=(Volumetric Flow Rate)/Area= 21.36/0.19635
=108.78 in/sec = 2.763 m/sec
Reynold's Number= (V* D_h)/ν =
((2.763)(0.0127))/0.00035738 = 98.187 (Laminar)
λ= 64/Re = 64/98.187 = 0.6518
Pressure Loss= λ(L/D_h )((ρ*V^2)/2)=0.6518(3.048/0.0127)[((818) 〖(2.763)〗^2)/2]= 488,439.4 Pa
I think this looks a little high, is all this correct, or did I botch it up somewhere?
Thanks,
Superfly





RE: Pressure Loss Calculations
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RE: Pressure Loss Calculations
So there are no numbers that look totally out of place? I'm just not very familiar with appropriate viscosities and velocities and piping sizes, things like that.
Thanks a lot!
Superfly
RE: Pressure Loss Calculations
Is this a school problem -- why are you converting back and forth from metric to Imperial units?
Patricia Lougheed
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RE: Pressure Loss Calculations
Its not a school problem, I am converting between units because I am much more comfortable doing the analysis in metric units (because of the viscosities and densities and such) but my boss wants to see imperial units on my calculations.
Anyway, I was only looking to calculate major pressure loss with this, which is why I didn't include any of the valves or elbows.
I am now trying to calculate the minor pressure loss and I just posted a thread on that, because I am again unsure of the numbers I am getting.
Also, sorry for the mix up, its all piping.
Thanks,
-Superfly