1 reply to this topic

[josh_l]

Hi,

I am wondering how can I estimate the Maximum capacity a steam pipe can pass.

for example: a 500 meter pipe is connected to a steam generator (any other gas is relevant as well).

the steam being generated is at 15 bars.

the 500 pipe is open to the atmosphere.

between the pipe and the steam generator, there is a shut off valve.

in some point, the shut off valve is opened.

If a 30 m/s velocity is needed, what diameter does the pipe need to be?


in all pipe sizing methods, I am asked to choose a flow rate, and according to it, choose a pipe size.
but how can I know if a pipe can actually pass the flow rate I choose?
also, the delta P is never being considered.
the pressue in the inlet and the flow rate I choose, determines the pressure drop per 100 feet and the pipe size.


in the example above, I dont have a control valve that allows me to control my flow rate- so what will be the flow rate in that case if 30 m/s is needed, and I have dP of 14 bars?



thank you,

Chen

Attached Files

•  steam generator.JPG   13.08KB   9 downloads

[Zauberberg]

The maximum mass flow rate one can see is the choked flow - there are two equations for (adiabatic and isothermal) flow of gas describing this phenomenon. That's at the same time the maximum theoretical "capacity" of the line. In reality you certainly design for lower velocities.

What is missing in your post is: how much flow do you need? And at what pressure you consider 30 m/sec?
You can have 30 m/sec velocity inside the line for infinite number of flow/DIA combinations.

High pressure steam headers and long lines are usually sized for <1.5 psi/100ft pressure drop, and the lines are sized for <30 ft/sec per inch of pipe diameter for smaller lines (<6") and 200 ft/sec for >6" lines. This figure can be increased up to 250 ft/sec if the steam is superheated.