DIERS Benchmarks

Case 8

Liquid Water   (Mach II  Single-Phase Engine)   Download

For the DIERS single-phase liquid water case the first design is with using the Mach II single-phase engine that uses the Darcy formula to calculate the pressure drop.  When you apply the Darcy formula and do not take any credit for loss of flow due to the inlet pressure drop, you are not able to achieve the 3% inlet pressure drop limit using either, 4", 6", or 8" inlet piping.  This problem is encountered a lot in industry and in some cases the designer would recommend a special reducer to reduce the inlet pressure loss.  The reducer resistance in most cases is the cause of the inlet pressure drop not being able to reduce the pressure drop below the 3% requried by Code.  However, we will take a look at the same problem using the Mach II two-phase design engine which uses direct integration of the VdP integral which will reduce the flow based on the inlet pressure loss.  See next tab for Liquid water two-phase design.

Mach II   Nozzle Results & Piping Restyles     

  Liquid Water                Flowrate (lbs/hr)         Choke (psia)           Quality (x)            Inlet dP / %Pset             Outlet dP /% Pset     Piping

                                                803,133                        -------                          0                        10.94 / 20.82                   4.02 / 7.66            4 X 6

                                               803,133.                        -------                          0                          3.15 / 6.0                         4.03 / 7.67            6 X 6

                                               803,133                         -------                          0                           2.2 / 4.2                           4.03 / 7.67           8 X 6