Calculate expected flow rate through a tube

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Calculate expected flow rate through a tube

Postby Drew » Fri Mar 11, 2011 3:50 am

Hi,
I was wondering if someone could assist me in working out the expected flow rate (or velocity is fine) in a horizontal stainless steel tube.

Given a head pressure of 30 meters, a tube (stainless steel) 6mm internal diameter of length 16 meters - how does one calculate the flow rate for water?

Any assistance would be much appreciated.
Drew
 
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Re: Calculate expected flow rate through a tube

Postby admin » Fri Mar 11, 2011 8:13 am

You must know pressure on the start and pressure on the end of pipe. Do you have any obstacles in pipeline? What is the difference in height from start to finish?
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Re: Calculate expected flow rate through a tube

Postby Drew » Fri Mar 11, 2011 7:05 pm

Pressure head at the start is 30 meters of water
End of the pipe is open - and no obstacle within pipe or at end.
water temp ambient (20C - 72f)
Starting height is equal to ending height (ie horizontally laid)
Drew
 
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Re: Calculate expected flow rate through a tube

Postby admin » Sat Mar 12, 2011 9:52 am

Here is the report that I have for your inputs:

Pipe pressure drop calculator CALCULATION REPORT
1. volume flow rate (q): q = 3.3384428 l/min
2. weight flow rate (w): w = 200.30681 kg/h
3. pipe length (L): L = 30 m
4. pipe diameter (D): D = 6 mm
5. pipe roughness (kr): kr = 0.1 mm
6. density (ρ): ρ = 1000 kg/m3
7. kinematic viscosity (ν): ν = 1.006 mm2/s
8. dynamic viscosity (μ): μ = 0.0010060001 Pas
9. K factor - minor lossed coefficient (K ): K = 0.0
10. velocity (V): V = 1.9678915 m/s
11. cross section area (A): A = 28.274336 mm2
12. friction coefficient (f): f = 0.030398201
13. Reynolds number (Re): Re = 11736.927
14. boundary layer (δ): δ = 0.10340908 mm
15. pressure on the pipe start (p1): p1 = 40.328747 mWS
16. pressure on the pipe end (p2): p2 = 10.328746 mWS
17. pressure drop (p1-p2): p1-p2 = 30 mWS

This report is generated using pressure drop calculator at:
http://www.pipeflowcalculations.com/pressuredrop/
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Re: Calculate expected flow rate through a tube

Postby Drew » Mon Mar 14, 2011 12:37 pm

Excellent - thanks for your help! I must have been looking at the wrong calculator!
Drew
 
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Re: Calculate expected flow rate through a tube

Postby Mark Reynolds » Thu Mar 17, 2011 8:33 pm

I also need to estimate a flow rate through a tube. This time assuming 100% toluene. I have the density (.87g/l) and viscosity (.68cSt) and viscosity inlet and outlet pressures (from a tank with 25psi head pressure into another tank at 12psi) , but need help finding the K value and Kr. Tube is 192" long combo of 3/4" ID stainless and teflon lined and I am ignoring a 7' static head at this time for a ballpark flowrate check.
Mark Reynolds
 
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Re: Calculate expected flow rate through a tube

Postby admin » Fri Mar 18, 2011 11:12 pm

Here is the report that I have for your inputs:

Pipe pressure drop calculator CALCULATION REPORT
1. volume flow rate (q): q = 8.040907 gpm US
2. weight flow rate (w): w = 58.381325 lb/min
3. pipe length (L): L = 192 ft
4 pipe diameter (D): D = 0.75 in
5. pipe roughness (kr): kr = 0.01 mm
6. density (ρ): ρ = 870 kg/m3
7. kinematic viscosity (ν): ν = 0.68 cSt
8. dynamic viscosity (μ): μ = 5.916E-004 Pas
9. K factor - minor lossed coefficient (K ): K = 0.0
10. velocity (V): V = 1.7798676 m/s
11. cross section area (A): A = 285.02295 mm2
12. friction coefficient (f): f = 0.021173518
13. Reynolds number (Re): Re = 49862.465
14. boundary layer (δ): δ = 0.09259989 mm
15. pressure on the pipe start (p1): p1 = 25 psi
16. pressure on the pipe end (p2): p2 = 12 psi
17. pressure drop (p1-p2): p1-p2 = 13 psi

Important things are - pressures are absolute - if not please use calculator and enter absolute values.
If you have no obstacles in pipe than K = 0. If not you must know number of elbows tees reducers valves pipe entrance and pipe exit.
You have all resistance coefficients at:
http://www.pipeflowcalculations.com/resistancecoefficientK/

Kr for stainless pipe I used 0.01 mm.

Used calculator is at:
http://www.pipeflowcalculations.com/pressuredrop/
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Re: Calculate expected flow rate through a tube

Postby Mark Reynolds » Wed Mar 23, 2011 11:33 pm

Ok I determined a K factor of 4.5 from the calculator. We have some unit errors on the calc above but when I try to re-run I get infinity for the friction coefficient. Some fields come pre-filled in the calculator and I can't edit. What is the preferred order of entry? First I am zeroing out any white fields and changing the unit selection, then entering my knowns, then calculate - then come the bid red box and no way to edit.

Looking for Q in liters per minute
L = 192 inches
D = 0.620 inches
P1 - P2 = 12 psi
density = .87 = 870 grams/liter
v = .68 Centistokes
K = 4.5
k = .01
Mark Reynolds
 
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Re: Calculate expected flow rate through a tube

Postby admin » Thu Mar 24, 2011 8:14 am

Here is what I have for your inputs:

Pipe pressure drop calculator CALCULATION REPORT
1. volume flow rate (q): q = 1615.3934 l/min
2. weight flow rate (w): w = 84.32364 kg/h
3. pipe length (L): L = 192 in
4. pipe diameter (D): D = 0.62 in
5. pipe roughness (kr): kr = 0.01 mm
6. density (ρ): ρ = 0.87 kg/m3
7. kinematic viscosity (ν): ν = 0.68 cSt
8. dynamic viscosity (μ): μ = 5.9160004E-007 Pas
9. K factor - minor lossed coefficient (K ): K = 4.5
10. velocity (V): V = 138.22519 m/s
11. cross section area (A): A = 194.77835 mm2
12. friction coefficient (f): f = 0.017615883
13. Reynolds number (Re): Re = 3201132.5
14. boundary layer (δ): δ = 0.0020060984 mm
15. pressure on the pipe start (p1): p1 = 27 psi
16. pressure on the pipe end (p2): p2 = 15 psi
17. pressure drop (p1-p2): p1-p2 = 12 psi

Values that you can not input are results that are calculated - do not need to enter them.
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Re: Calculate expected flow rate through a tube

Postby Mike » Fri May 20, 2011 5:48 pm

As a newbie this post provided two examples that allowed me to check that I was using the flow rate calculator corrrectly. Let me summarize the examples in a way that may help other newbies.

You simply input these 7 items: the report numbers these as 3-7, 9, and 17. Item 15 is required but does not affect the calculation, so put in any number.

INPUT ITEMS
3. pipe length (L): L = 30 m
4. pipe diameter (D): D = 6 mm
5. pipe roughness (kr): kr = 0.1 mm
6. density (rho): rho = 1000 kg/m3
7. kinematic viscosity (mu): mu = 1.006 mm2/s
9. K factor - minor lossed coefficient (K ): K = 0.0
15. pressure on the pipe start (p1): p1 = 40.328747 mWS
17. pressure drop (p1-p2): p1-p2 = 30 mWS

CALCULATED RESULTS
1. volume flow rate (q): q = 3.3384428 l/min
2. weight flow rate (w): w = 200.30681 kg/h
8. dynamic viscosity (µ): µ = 0.0010060001 Pas
10. velocity (V): V = 1.9678915 m/s
11. cross section area (A): A = 28.274336 mm2
12. friction coefficient (f): f = 0.030398201
13. Reynolds number (Re): Re = 11736.927
14. boundary layer (d): d = 0.10340908 mm
16. pressure on the pipe end (p2): p2 = 10.328746 mWS

And for the second example you just input these items:
3. pipe length (L): L = 192 in
4. pipe diameter (D): D = 0.62 in
5. pipe roughness (kr): kr = 0.01 mm
6. density (ρ): ρ = 0.87 kg/m3
7. kinematic viscosity (ν): ν = 0.68 cSt
9. K factor - minor lossed coefficient (K ): K = 4.5
15. pressure on the pipe start (p1): p1 = 27 psi
17. pressure drop (p1-p2): p1-p2 = 12 psi
Mike
 
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