How to calcuate the pressure calculation

[stberry]

Hello,

I would like to know how to calculate the situation below.
There is a pipe which have 10 holes having 8 mm diameter.
The pipe is 5 meter long and inside diameter of the pipe is 10mm . The holes on the pipe are evenly devided.
The pipe is located 50 mm high from the bottom of a tank which has water 5 meter high.
5 bar.g air is fed into the one side of the pipe and the other side of the pipe is blocked. Therefore air can be blown out only through the 10 holes.

I want to know pressures at the each hole and how to calculate it.

It would be highly appreciated if anyone help me.

 

[Artisi]

Is this an operating system, in design or a school project?

 

[stberry]

This is operation condition but simplified because I can't explain all conditions.

Thanks

 

[Compositepro]

Do you mean 10 cm diameter pipe?

 

[stberry]

Inside of the pipe is 10 mm not 10 cm.

Thanks

 

[stberry]

Sorry, I correct the hole size.
Diameter of the hole size is 2 mm not 8 mm.

 

[MortenA]

calculate flow for a hole and check linear velocity in pipe for 10 times one hole. If the velocity is low say<0.1 mach then i think dP in the pipe is low and pressure in the pipe will be 5 barg. If not - find the thinking hat ;-)

Best regards

Morten

 

[Artisi]

MortenA - I tend to agree with your comment, for the low airflow, pressure differential across the exit holes etc. the pressure at each would be something just less than 5Bar and probably not worth the hassle of making complicated calculations to get an academic answer of something like 4.8765432 bar I

 

[djack77494]

I'm forced to agree with the assessment that the dP will be (roughly) 5 bard(differential) less the liquid hydrostatic head (5.05m). It's not too hard to complete the calculation and get the flowrate as well. Since the cross sectional area of all 10 holes is less than half that of the "header", I deem it safe to neglect frictional losses in the header. So what you have is approximately 10 parallel 2mm orifices; calculated the dP using an orifice dP formula with 1/10 the total flow. Then you'll have the flow as well.
Happy computing,
Doug

 

[stberry]

Thank you very much djack77494

The condition above is simplized in order to ease calculation. Actual status is that sum of all cross sectional area of the holes are much bigger than the head's.
therefore the current situation of our plant is that there is no flow at the last hole. So I have to reduce the quanity of the holes. If I learn how to calculate the pressure drop at each hole, I can decide the quantity of the holes.
I would really appreciate it if anybody including djack77494 solves my problem.

Thank you in advance.

 

[MortenA]

i have a hard time believing this

Are you sure that the pressure in the header IS 5 barg? If the total flow is higher than your max. supply rate then thepressure may actually be lower?

You can use the API 520 formula to calculate flow from a single hole (sec 3.6.2 or if you dont have API 520 check out the

Best regards

Morten

 

[stberry]

Thank you MortenA

sorry for confusing you.

I don't know the pressure of head since there is no gauge. 5 bar.g air is indicated from 10 meters long from the head.
Unluckily, I don't have API520, could you help me out?

With best regards,

 

[MortenA]

Most of the sizing stuff from API 520 is contained in the Crosby engineering hand book:

http://www.tycoflowcontrol-na.com/ld/CROMC-0296-US.pdf

note that this is supplied free from the vendor.

Best regards

Morten

 

[gio1]

A sealed tank is filled with gaseous CO2 at 200F and 200Psi.
Is there any substance which if introduced in the tank could react with CO2 and reduce the pressure?

Thanks

Gio1

 

[gio1]

sorry for my previous post - wrong thread