Air Flow Rate

[3243]

Hi, I need some help on what equations to used, I need to find the Air Flow Rate in a pipe. Air is compressed in a tank, it comes out in a pipe of 3" diameter then it goes thru a 1" orifice(length less than 1/2&quot and goes back to a 3" pipe. The inlet pressure is 35psi and oulet pressure is 27psi (controlled). Do I need the Length of all the pipe or what?, please help me with this problem by telling me what formulas and procedure to use, thank you very much.
the equations i am trying to use are:
v=((25000dp)/L)^(1/2)
Q=Av
What else do I need, how do I find the pressure loss do to pipe length,
thanks for your help.
EJ

 

[TD2K]

How long is the amount of 3" pipe? If it's short, it's effect is minor compared to the 1" restriction. If you have a mile of it, that's another matter.

I'd suggest you get a copy of Crane technical paper 410C (about $40), one of the best investments you'll make in your career.

ASSUMING you have a short length of 3" line, I got the following flowrates:

5' of 3" pipe, 1580 lb/hr
50' of 3" pipe, 1569 lb/hr
100' of 3" pipe, 1557 lb/hr
10 miles of 3" pipe -)), 371 lb/hr

 

[3243]

Hi, I still dont know how to find the airflow rate (ft^3/min) what equations should I used??, to find it with the 1" restriction?. is it the equations I wrote before or do I need more Equations. the 3" pipe is about 50', so the velocity you told me must be ok, but aren't there any loss because of the 50' length, and what equation do i used to find the airflow?????, thanks for responding

EJ

 

[sciguyjim]

I don't know if any of this will be helpful to you but just in case it is, here is some info I have on hand (I found it in a library book):

All data is for a 3" diam pipe:

The pressure drop in inches of water at the listed air velocity per 100' of pipe:

Velocity....Pressure Drop
3500'/min....7.5" water
4000'/min...10.0" water
4500'/min...11.0" water

Airflow volume at 4500'/min = 220 CFM

 

[TD2K]

Sciguyjim, pressure drops for gases are a function of pressure and temperature (and composition but in this case, we've all agreed we are talking about air), neither of which you have provided with this 'reference' or even bothered to wonder about. Looking at the data it's pretty obvious this is pressure drop data for air in a 3" pipe at atmospheric pressure.

It has NOTHING to do with the OP's question and is highly misleading.

 

[TD2K]

Sorry, the "or even bothered to wonder about" was out of line.

 

[sciguyjim]

Ok, well, that's all the info I had. I guess I wasn't any help after all. I'll try to be more careful in the future.

 

[3243]

Hi again, where can I find the crane handbook, because someone sent me some of the pages I needed but not all the ones I need, I need a table to find all the properties, and Cv and Cp and all other numbers I need, also How Do I find the velocity?, I need the ratio,k, of specific heat at const. pressure to specific heat at const. volume, Cp/Cv.
I also dont have the pages A-23 and A-24 , I only have A-25, Is there anyway you can email me this pages, or tell me where to find them online,
thank you for you help
EJ

 

[TD2K]

http://www.cranevalve.com/tech.htm

 

[Haf]

3243,

Crane Technical Paper 410C is a copyrighted document (which should have been clear to you when TD2K posted that it costs about $40).

It's one thing that your grasp of these concepts is remedial at best (I don't see how any mechanical engineer could not know k for air, or at least not know that you could easily find that in ANY fluids, heat transfer, or thermodynamics textbook), but requesting free copies of copyrighted documents is UNETHICAL.

Please refrain from such unscrupulous requests in the future.

Haf

 

[3243]

hi, thanks for all your help, I have already ordered the crane technical paper 410C when TD2k told me about it, but it takes 5 to 6 days to get here, sorry I just needed a table not specifically the crane one, but any online to solve the problem i had. the K I was refering was K as resistance, but I already figured it out, thanks for your help. and sorry for any inconvinience.
Thanks