## calculating N2 flow through a flexible hose

## calculating N2 flow through a flexible hose

(OP)

I am trying to determine the flowrate of nitrogen (90 psig) through a flexible rubber utility hose. I found some online calculators, but want to do some hand calculations to validate. I guess I am looking for friction factor for 3/4" id rubber hose and any other tips. The hose lengths would be 25 feet and 50 feet lengths. Thanks

## RE: calculating N2 flow through a flexible hose

## RE: calculating N2 flow through a flexible hose

## RE: calculating N2 flow through a flexible hose

I recommend Crane's Technical Paper 410. Google it and buy it on the net. I suspect the flow will be close to fully turbulent and there's a couple graphs and a table in TP410 you can get the friction factor from.

Good luck,

Latexman

## RE: calculating N2 flow through a flexible hose

With an supply pressure of 90 psig to 1 atmosphere.

I think you will get critical flow through the hose....

## RE: calculating N2 flow through a flexible hose

Katmar Software

Engineering & Risk Analysis Software

http://katmarsoftware.com

## RE: calculating N2 flow through a flexible hose

## RE: calculating N2 flow through a flexible hose

K = fL/D = (0.245)(25*12)/0.75 ~ 100

dP/P

_{1}' = (90-15)/104.7 = 0.716For sonic velocity dP/P

_{1}' = 0.926 for K = 100Therefore, flow is not sonic for 25' and 50' with 15 psig discharge pressure.

Good luck,

Latexman

## RE: calculating N2 flow through a flexible hose

## RE: calculating N2 flow through a flexible hose

Good luck,

Latexman

## RE: calculating N2 flow through a flexible hose

For sonic velocity dP/P

_{1}' = 0.784 for K = 10Therefore, flow is still not sonic for 25' and 50' with 15 psig discharge pressure.

Good luck,

Latexman

## RE: calculating N2 flow through a flexible hose

In order to get a friction factor of 0.0245 (as used by Latexman) you need a roughness of about 0.002", which would be typical of commercial steel pipe. The roughness I would use for smooth PVC pipe would be 0.0002" and this would give a friction factor of 0.015 and would predict supersonic flow. In my earlier calc I took the roughness as 0.0004" (twice that for PVC). Fortunately, as you get close to supersonic flow the actual flowrate does not vary much with end pressure so it is not too important.

Katmar Software

Engineering & Risk Analysis Software

http://katmarsoftware.com