Regarding the issue of flow rate
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Conditions: 10 MPa nitrogen is used to purge the filter in a device operating at a pressure of 9 MPa; the pressure difference between the nitrogen and the pressure inside the device is 1.0 MPa. During the purging process, the inlet nitrogen pressure remains constant, while the pressure inside the device stays at 9 MPa. It is assumed that the nitrogen flow rate is 30 m³/s, as long as the pipe diameter meets the requirements. Can the backflow rate be calculated under these conditions? If not, then how can we design the diameter of this backflow pipe?
With the pipe diameter, flow rate, and pressure known, it’s just a matter of doing some arithmetic; so why can’t I calculate it?
There is no specification for the pipe diameter; only the pressure difference and safe flow rate are specified. As for the pipe diameter, I think it’s sufficient as long as it meets the requirements, but there’s no fixed value specified
How can the inlet pressure be kept constant if the pipe diameter is not large enough? The filter purge should be pulsed, with a high initial velocity. Your inlet is constant at 10 and the device is constant at 9; is it blowing at a steady gas flow rate? With a constant pressure difference of 1 Mpa, how severe must the blockage be to maintain this level? The purging effect will definitely be very poor. Under pulsation, there are ten unsteady processes, with the pressure difference across the two ends gradually decreasing
The air source at the inlet is equipped with a buffer tank; for the purpose of purging the pipeline inlet alone, this source pressure is likely to be variable as well. Is it possible to carry out calculations under these conditions?
I’ve never done filter purging, so I don’t know much about it. It seems strange no matter how you look at it; maybe your logic is incorrect. If you want to perform backwashing on the filter, you first need to determine what flow rate is required to achieve an effective backwashing effect, and then figure out how to generate that flow rate for the backwashing process. Since a pressure difference of 1 Mpa is available, the gas velocity used for pulse cleaning can be set to a value of a few times the speed of sound.
Well, that’s correct. We should first figure out the typical flow rate that can be flushed through, and then determine the pipe diameter; the pressure difference is just a prerequisite and isn’t decisive. Thanks, it seems I know how to calculate it now
If there is pressure control on the nitrogen tank ahead, a pressure difference of 1 MPa begins to act on the filter element. After the filter element is cleaned, in order to maintain pressure, the outlet control valve of the buffer tank closes down, and most of the pressure difference acts on this control valve. So there is no need to consider the pipe diameter; simply consult the manual to find the corresponding purge pipe diameter based on the filter size.
I need to check that manual. Can it be written down? Thank you
It’s in many process design manuals; I’ll take a look tomorrow and send you a photo.