1 Reply Latest reply on Jul 25, 2011 8:33 AM by Rich Bayless

    Sonic Flow Pipe Exit

    Dave Frenk

      Perhaps someone has an answer to this problem I have. After running multiple flow simulations on a piping discharge from a relief valve the results show the gas velocity greater than mach 1, which cannot happen. See link below.

       

      http://www.pipeflowcalculations.com/pipeflowtheory/maximum-flow-of-gases.php

       

       

      Here are the conditions I'm using:

       

      -methane

      -pipe size 3", discharge from 3" pipe after an elbow

      -inlet pressure (initial condition): 1670 psi

      -inlet temp (initial condition): 135F

      -outlet static pressure (boundary condition): 14.7 psi

       

      The resulting mach number at the exit is 4.3, using the high mach flow option.

       

      I'm not sure if I have the boundary conditions setup incorrectly or what else I can change.

       

      Goal NameUnitValueAveraged ValueMinimum ValueMaximum Value
      Static pressure inlet [lbf/in^2]1498.371497.491496.981498.37
      Static pressure outlet [lbf/in^2]14.7014.7014.7014.70
      Mass flow [lb/s]-28.63-28.64-28.65-28.63
      Velocity outlet [ft/s]1791.141789.881788.921791.14
      Velocity inlet [ft/s]637.21637.70637.21638.05
      Mach number outlet [ ]4.344.344.344.34

       

      I appreciate any feedback. I can send the solid models if anyone is interested.

       

      Dave