The aim of this work is to describe the design and the use of an innovative test rig for investigating the expansion of saturated fluids inside a converging nozzle and the evolution of two-phase flows in Tesla-type turbines. The flow exiting the nozzle enters a thin circular chamber and it finally is discharged in the center through a duct perpendicular to it. The experimental test rig has two nozzles placed in diametric position. This peculiar shape reproduces the geometry of a single gap between two discs of a Tesla turbine, a machine that potentially could replace the expansion valve in chillers and heat pumps to increase COP. The study of a simple and static geometry is necessary in order to calibrate the CFD modeling of the phase change in nozzle and rotor chamber. The rig was designed and assembled by TPG of the University of Genoa in the framework of the Pump-Heat H2020 project.Here it is used saturated water and in order to fully characterize the expansion conditions the rig has been equipped with pressure sensors at the nozzle inlet and at the rig outlet, a Coriolis mass flow meter, and a temperature sensor (nozzle inlet). A high-resolution camera was used to look at the position and shape of front of the phase change along and around the nozzle as a function of varying pressure and temperature conditions of the fluid. The tests were performed in the 2-6barA pressure range and 120-160°C as temperature range, feeding either one or both nozzles.Future work involves the use of different nozzle profiles, such as a convergent/divergent to test both subsonic and supersonic flows, and finding experimental results necessary to optimize the geometry of nozzles and Tesla turbines in two-phase applications.

Design and Testing of a Static Rig for Tesla Turbine Flow Visualization

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2021/volume/84898

Turbo Expo 2021

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