Thermo- and fluid dynamic model of a multiphase screw pump, operating at very high gas volume fractions

To describe the performance as well as the thermodynamic behaviour of a multiphase screw pump, also operating at very high gas volume fractions up to 100 %, a new thermo- and fluid dynamic model was developed. The model, which will be presented in this paper, takes the time-dependent gas-liquid heat transfer, the compressibility and acceleration effects of the multiphase gap flow as well as the possibility of critical flow conditions into account. For the simulation of the mutual phase heat transfer, the solution of the gap flow conservation equations and the optimisation of the gap inflow velocity, different numerical techniques were used. The model as such gives important information of the pressure and the temperature distribution, the multiphase leakage flows through the chamber connecting gaps as well as the effective flow rate or the volumetric efficiency of the pump near the conveyance break-off at very high gas volume fractions.