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Pressure drop

Pressure drop

Pressure drop

(OP)
Hi,

I am trying to determine the pressure drop across a pipe reduction, from 6" pipe to 1" pipe.  The volumetric flow rate is 4.5m3/min.

Is there a k value for a reduction of this size? or is there an equivalent length for a reduction in pipe of this magnitude?

I would like to see how the pressure varies as the flow rate varies.
assume kinematic viscosity = 0.0000011m2/s
Density = 998kg/m3

Any help with this problem would be greatly appreciated
 

RE: Pressure drop

I would be more interested in the friction loss in 1" pipe than any pressure drop from 6" to 1" at 4.5m3/min. or is this a typo and it should be 0.45m3/min.

RE: Pressure drop

Agree with Artisi. Depending upon the length of the 1" section the friction loss there will be much more of importance.  

RE: Pressure drop

(OP)
Should have been more clear.  the 6inch line has a 1" nozzle on the end.  I am interested to find out how much backpressure or restriction the nozzle has.  And yes I do mean 4.5m3/min.

RE: Pressure drop

Yes considering the head loss at this flowrate(approx 1200USgpm) thru 1" dia. pipe is somethging like 700ft loss for a 1'(one foot) length of pipe.  

RE: Pressure drop

(OP)
there is not a length of 1" pipe it is simply a nozzle (1inch in diamter) on the end of the 6inch pipe.  This device is used for cutting rock.  I am working out all the pressure losses through the pipe (i.e valves etc.) and would like to know how much pressure loss will result from the reduction due to the nozzle.

RE: Pressure drop

Sorry was sending my last message as you were posting-
suggest you google flow through nozzles - a heap of info there for you.

RE: Pressure drop

"I would like to see how the pressure varies as the flow rate varies."

The pressure varies as the square of the flowrate.

Double the flowrate the presure increeases x 4
 

RE: Pressure drop

2720 psi at 4.5 m³/min and 1" nozzle size.

RE: Pressure drop

(OP)
Can you explain how you got 2720psi? seems very high for a line component pressure drop even at this high flow rate.
 

RE: Pressure drop

Engprofile, please also see my post in the thread "Flow through pipe at 40 psi".

To accelerate the water to give 4.5 m3/min through a 1" nozzle (i.e. 440 ft/sec) takes 1300 psi.  The pressure drop through the 6" to 1" reducer will depend on the profile of the reducer.  A 30 degree conical reducer would give a pressure drop of about 300 psi. So I would say you need about 1600 psi in the 6" pipe to give this flow.

All numbers are approximate because we do not have accurate dimensions.

Katmar Software
Engineering & Risk Analysis Software
http://katmarsoftware.com

RE: Pressure drop

I used velocity² x density/2. That gives me the pressure. But I just discover that I made a mistake when calculating the velocity. 1585 psi is now what my calculation leads to. Sorry! I used 25.4 mm nozzle diameter.

RE: Pressure drop

Katmar,

Don't know whether you've read my post (ref. 23 Jun 10 5:41). Using the approach reported there I got approx 2900 psi pressure drop (with a coefficient of discharge C = 0.95). Cannot understand how you've calculated 1600 psi, could you expand?
 

RE: Pressure drop

ione, I used the same approach as micalbrch, except that I took my ID as 26.64 mm and got 1300 psi as the velocity head. If I use 25.4 mm I get the same value as as micalbrch. I got 300 psi for the reducer using a correlation by Hooper (the 2K man) for a conical reducer. If I substitute a sudden reduction for the reducer I get 930 psi. Adding the sudden reduction to the velocity head (for 25.4 mm) gives 1585+930=2515 psi. You and I are within 13% of each other. Without detailed drawings of what it all looks like I would not argue over that difference.

Katmar Software
Engineering & Risk Analysis Software
http://katmarsoftware.com

RE: Pressure drop

katmar,

thanks for your swift and detailed (as always) reply.

RE: Pressure drop

(OP)
Thanks everyone for this very useful information.  Problem solved.

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