Flow rate that the DN20 nitrogen pipeline can achieve
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Nitrogen at 55 bar is to be depressurized and sent to a storage tank at 25 bar; a DN20 pipe (six-pipe fitting) is used for this purpose. What is the flow rate that this pipeline can achieve in NM3/H? Which formula is being used?
According to Page P3-74 of the \"Chemical Process Design Manual\" (available for download on this forum), the flow rate should be between 2 and 5 M/S; I recommend using 3 m/S. Please carry out the calculations yourself. http://bbs.hcbbs.com/viewthread.php?tid=223720&highlight=%BB%AF%B9%A4%B9%A4%D2%D5%C9%E8%BC%C6%CA%D6%B2%E1
This post was last edited by lxy6240@tom.com on 2010-3-25 at 11:02. Thank you to the person who replied above; I have one more small question. Consider it a way of asking for your help. Once we know the flow rate, do we just multiply it by the cross-sectional area of the pipe, which is 1/4 πd2, to get the flow volume? I calculated that it’s only 3.39 NM3/H, which seems too low. Should the conveying pressure and the pressure difference before and after also be considered?
In the end, I calculated it like this: V2 = P1/P2 × V1 = 26 bar/1 bar × 3.39 m3/h = 88 NM3/h. It seems reasonable; what do you all think?
This post was last edited by lim927 on 2010-3-25 at 11:37. Essentially, it involves using the formula for volumetric flow rate and area (after unit conversion, this becomes d=18.81*sqrt(V/u) as shown in various manuals), and then converting V to cubic units. Note that V represents the actual flow rate at the actual absolute pressure, while the nominal value corresponds to the flow rate at 1 bar and 0 degrees Celsius (the temperature can be ignored for rough estimates). At a flow velocity of 3 m/s, the flow rate at 26 bar (I thought the absolute pressure was 25 earlier) is approximately 88 Nm3/h (estimated value)
That 3.39 of yours should be in m3/h, not Nm3/h. Even after multiplying by 26, it doesn’t give an accurate value in cubic meters, as the temperature isn’t taken into account
It has been sent to the design institute, and their calculated value is over 20 cubic meters per hour. Is anyone from the design institute here? Give a clear answer first!
I guess I’d better ask them how they do the calculations. I’m not from a design firm, but I’ve calculated nitrogen pipelines before, and that’s how it’s done. I’ll wait for someone more experienced
I posted this thread in the “Process and System Design Discussion Area” as well, to see what experts in design have to say.
Using the economic flow rate for pipes, it is approximately 17 NM3/h