I would like to know how to calculate the velocity of the gaz in outlet nozzle of separator.
It is a 2 phases separator. I have the flow, the density, the viscosity of the gas.
I examined several gas condensate separators designs and found values in the range 30-50 m/s for velocity in inlet/outlet lines at operating consitions, however these should have a limited influence in separation process, the efficency being determined mainly by the vertical velocity, the turbolence etc. etc. inside the separator...
In my experience the value you mentioned (180 m/s) seems a bit too high for a natural gas line (but could be acceptable for different purposes), I would check the values of gas density and flow, then calculate the speed of sound and compare values with the velocity at maximum flow.
assuming MMscfd as million standard cubic feet per day and
presuming natural gas with a density of 0.75 Kg/M3 (at std. cond.)
10 MMscfd -> 10 * 1000000 MMscfd / 35.31 / 3600 -> SM3/s * 0.75 Kg/M3 -> 58.95 kg/s
58.95kg/s -> 58.95Kg/s / 33Kg/M3 -> 1.78 M3/s (at operating conditions)
internal area (6 inches) -> 0.017 M2
1.78 M3/s / 0.017M2
should be something about 100 M/s
(hoping there are not too much errors in my conversion...)
you can calculate the speed of sound with a process simulator or some free tool as for example
assuming MMscfd as million standard cubic feet per day and
presuming natural gas with a density of 0.75 Kg/M3 (at std. cond.)
10 MMscfd -> 10 * 1000000 MMscfd / 35.31 / 86400 -> SM3/s * 0.75 Kg/M3 -> 2.45 kg/s
2.45kg/s -> 2.45Kg/s / 33Kg/M3 -> 0.075 M3/s (at operating conditions)
internal area (6 inches) -> 0.017 M2
0.075 M3/s / 0.017M2
should be something about 5 M/s
(sorry, out of office and doing conversions by hand...)
you haven't specified composition so I presumed a gas with a density (at standard conditions) of 0.75 Kg/M3, change this value if you have a different gas composition.