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losses from valves/bends

losses from valves/bends

losses from valves/bends

What would the typical loss value in a simple pipe system introduced by the following :
a) A 90 degree bend reducing internal diameter from 50mm to 20mm.
b) A stop valve.

RE: losses from valves/bends

I beleive will will need more info. ( hydraulic/ air )
Flow rate (GPM/LPM), fluid viscosity and
specific gravity

Assume 50 GPM is flowing through 1 1/4" schedule 80 pipe. Viscosity is 100SUS and specific gravity is .865.
pressure drop through 90 deg. tube bend = .2 PSI
Assuming standard bend radius.
pressure drop through 90 deg. sec. 80 elbow = .9 PSI
I have the formulas, which I'll be glad to fax to you.

RE: losses from valves/bends

Hello hydralph,
First of all I would like to thank you for taking an interest in my question.
I will give you the out line for the system.
The system consists of a pump which circulates fluid through a 3 metre length of 50mm diameter via a 90 degree elbow to a 10 metre legnth of 20mm diameter pipe. There is a stop valve on the output side of the pipe(The remainder of the system can be ignored)
Fluid density: 850kg/m3
Flow rate : 1.5 litres/second
Viscosity of fluid:0.02Ns/M2
As you may have guessed this is for a mechanical science assignment and the qustions are to find;
1 a)the reynolds number for the 50mm diameter section.
b)" " " " " 20mm " " " .
2 a)the head loss through the 50mm " " " "
b)" " " " " 20mm " " " " .
3 The power required for a pump to supply fluid through the system (pump is 70% effeicent)
4 The heat transfer for the 20mm section if fluid flow is at 70 degrees C,outer surface of pipe is at 18 degrees C Wall thickness is 3mm the pipe is of steel.
I have assumed a number of things :k=55 and that heat transfers radially and that the diameters given are inside diameters and that the system is on the horizontal plane.
I have some figures for the whole assignment but for extra marks I would like to mention the losses from the valve and the elbow

RE: losses from valves/bends

Best bet is to get some reference books from the libary or from a leading hydraulic manufactor. Parker Hannifin Corp.,
has a number of hand books available, (parker.com.).
I have bulletin # 0222-b2, Analyzing Hydraulic Systems.
I'm not sure if mine is still available, seeing I got it more years ago than I would like to remember. But it has all of the info. you would need. I beleive they charge a minimum fee for the books, but if you contact them I think they will send what you need. I'm also glad to see that school is spending time on laminar and turbulent flow. I use it every day in the real hydraulic world.
Your input HP is the easy one, covered in any hydraulic book. ( gpm x psi / 1714 x efficiency (overall).
Again, If you need any other info. I can fax it to ya.

RE: losses from valves/bends

Hey Paul,

I agree with Ralph. Another source of information is the Crane Technical Paper 410. It can be obtained from Crane. They also have a Windows based program for solving such problems. The software looks up all the information based on your input of fluid, fluid temperature, and system components.



Tom Worthington

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