Thermodynamic Model of a Twin-Screw Multiphase Pump

The twin-screw multiphase pump has been studied as an alternative system to substitute the conventional one (fluid separation, liquid pumping and gas compression) in petroleum boosting. By “pumping” simultaneously gas and liquid, the multiphase pump could reduce production costs in deepwater activities. This paper presents a thermodynamic model of a twin-screw multiphase pump to determine performance parameters such as: absorbed power, discharge conditions and efficiency. To overcome problems with the complex flow field inside of this novel equipment, the multiphase flow was divided into a sequence of simpler processes. Such approach helps determine energy and mass balances and enables the use of a process simulator (Hysys.Process v2.1) to construct the model. The model prediction when compared to the literature show that the assumption of a smooth turbulent flow, considering the pressure loss in the entrance and discharge of the gap, fits better the phenomena than the turbulent flow when calculating the flow through the gaps. In addition, the comparison for absorbed power indicates that the assumption of gaps filled only with liquid is not valid under all operation conditions.