DIERS Benchmarks

Two-phase Flashing Flow case # 2                          Download

For the DIERS two-phase flashing flow a two-phase fluid (steam), at a relieving pressure of 72.5 psia and a quality of 0.01 is allowed to flash as it flows through the inlet pipe, entering  the nozzle ( 4 P 6), and exiting through the discharge pipe.  The Mach II uses the direct integration(HDI), of the VdP integral to calculate the maximum fluid flux(Gmax) through the relief nozzle which sets the basis for the relief design.  Below you can view the results for the nozzle and you can view a snap shot of the direct integration table along with a graph showing the flow rate as a function of pressure.  The flow reaches a maximum flux(Gmax) which can be seen from the integration table and also as the point of discontinuity on the graph.

Two-phase high viscosity Flashing Flow case # 4

Next we will take the case of two-phase high viscosity flashing flow.  The case will be the same as the above case #2 except that the viscosity will change as a function of temperature by the equation:  µ = exp (A + B/ToK) .   A = 2959.3 and B = -1.74.

 Results Two-phase Flashing Flow

                       Flow rate (lbs/hr)              Choke(psia)        Quality         inept dP / %Pset     Outlet dP /%Pset             Piping

                          95,104                              58.9                   0.0287                  --------                       -------                          nozzle

                          92,362                              56.8                    0.0272              1.4 / 2.6                      4.9 / 9.4                         4 X 6

                          92,653                              57.9                    0.026               0.75 / 1.4                      5.1/ 9.8                          6 X 6

                          93,570                              59.0                    0.026               0.75 / 1.4                     1.0 / 2.0                          6 X 8

Results Two-phase High Viscosity Flahisng Flow

                         95,104                              58.9                    0.025                 ---------                        ---------                            nozzle

                         88,216                              54.3                    0.030                3.1 / 5.9                        8.2 / 15.7                       4 X 6

                         92,474                              57.1                    0.027                1.3 ? 2.5                       9.0 17.1                          6 X 6