# Calculate steam flow rate with pressure difference

So I have a 4-inch pipe with a pressure of 1.5 bar drop to 1.01325 bar, with a temperature of 120 degrees Celsius. How can I calculate or estimate the steam flow rate for this system?

• I do not know much about the subject, but I think that formulas exist for calculating what you are asking ... i would also think that the length of the pipe may be a factor, as well as possibly the pipe cross section shape Jul 1, 2022 at 16:09
• I have no formulas for it. But check if this has something usable for you: forbesmarshall.com/Knowledge/SteamPedia At least it may reveal something useful that you haven't thought.
– user33233
Jul 1, 2022 at 20:58

$$\Delta P = \left(\frac{fL}{D} \right)\frac{1}{2} \rho \left( \frac{Q}{A} \right) ^2$$
Where $$L$$, $$D$$, and $$A$$ are the length, inner diameter, and cross sectional area of your pipe, $$Q$$ is the volume flow rate you are after (e.g. in $$m^3/s$$),$$\rho$$ is the density that you would look up in a steam table for your temp and pressure conditions, $$\Delta P$$ is your overall pressure drop which you know, and $$f$$ is a friction factor that you can estimate using a Moody chart for the type of pipe you have.