flow of a methane gas tube

[mir]

Hello, gaseous question:
I have a tank that produces 500 mc/h of methane with a pressure of 1 bar... what pipe do I have to mount to keep the 500 mc/h out of the tank?

I thought I was on 3"

I used the formula:
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

q=port
d=diameter tube
v=speed

place diameter to 90mm and q=500 mc/h I get a flow to 22 m/s .... What do you say?

Thank you.
♪

 

[stevie]

I say that the outflow of a gas is not calculated so, but you have to know the pressure conditions upstream and downstream and from these calculate the speed of efflux multiplied by the passage section determines the actual transportable flow.

 

[mir]

I understand... but the flow formula should still be correct... it is obvious that that flow is linked to the pressure change.
What I don't understand is the criticality on the speed of the gas flow ... in theory I could put a small tube at very high speed!

 

[maxopus]

I don't know what the speed data normally used for methane gas.
a feeling would be to say that 22 m/s are many but, I think it is the case to check with someone who does this job.

 

[mir]

... on the net I don't find much...

 

[mir]

Let's see a little using bernoulli:

(p1+1/2*rho*v1^2-p2)/(1/2*rho)

v1=0 m/s
p1=0.5 atm
p2=0.3 atm
rho = 0,00071682 kg/mc

I get v2=23.6 m/s

Does that sound right?

Hi.
♪

 

[MBT]

Let's see a little using bernoulli:

(p1+1/2*rho*v1^2-p2)/(1/2*rho)

v1=0 m/s
p1=0.5 atm
p2=0.3 atm
rho = 0,00071682 kg/mc

I get v2=23.6 m/s

Does that sound right?

Hi.
♪

gas??

you can do, but bernoulli is only valid for fluids whose difference of viscosity is negligible. . .
I ask the office technologists what they use for calculating methane flows in our plants.

 

[stevie]

the equation of bernol is valid for incomprimible fluids, i.e. when the density is constant. in the case of a gas that varies its density according to the pressure things are more complicated.
I found this link I think you will be useful:
http://diem1.ing.unibo.it/personale/cazzoli/efflussoadiabatico.pdfeven if it is the ideal case adiabatico from however a good approximation of the results. considear the adiabatic constant k equal to 1.3.

 

[mir]

Many thanks but I don't get something back... from formula to page1 (the one with rectangle around) I enter the following data:

K=1.3
p0t= 0.5 atm = 50662.5 [kg/(m s^2)]p1 = 0.3 atm = 30397.5 [kg/(m s^2)]density = 0.00071682

I get an absurd speed = 8351 m/s

Where am I wrong?

Thank you.
♪

 

[maxopus]

Many thanks but I don't get something back... from formula to page1 (the one with rectangle around) I enter the following data:

K=1.3
p0t= 0.5 atm = 50662.5 [kg/(m s^2)]p1 = 0.3 atm = 30397.5 [kg/(m s^2)]density = 0.00071682

I get an absurd speed = 8351 m/s

Where am I wrong?

Thank you.
♪

Well, more than 8 km per second... in 5 minutes the gas sent from the syberia arrives in Italy, it is not bad. :biggrin::biggrin:

 

[mir]

My goal is 300000 km per second

 

[maxopus]

However, there is something wrong with formulas... even density seems wrong.
In practice, 1 cubic meter of gas should weigh 0.7 grams... doesn't it look cheap?