Preview on new features in TwinMesh™ 2019: CFD simulation of a SRM screw compressor with heating of rotor and casing solids with ANSYS CFX.

On the right hand side, solid surface temperatures are shown, on the left hand side the temperature on two perpendicular section planes in solids and fluid. To account for Conjugate Heat Transfer (CHT), fluid-solid interfaces are necessary in ANSYS CFX. They are used here to connect the rotor solids to the fluid region. But the outer radial interfaces have to be defined as fluid-fluid interfaces to connect them to the stator fluid parts, i.e. the inlet and outlet ports. Only at the non-overlapping parts of these interfaces, they should be connected to the casing solid.

CFX Berlin implemented User Fortran routines that connect these non-overlapping parts of the fluid-fluid interfaces to the interior solid surfaces to account for temperature and heat flux exchange. With this new TwinMesh beta feature, TwinMesh users can fully simulate CFD and CHT cases. The case in the animation was initialised with 70 C° in the rotors and 20 C° in the casing, which is also the inlet temperature of air. The air is compressed from 1 bar to 3 bar at 12,333 rpm; the shaft ends are set to 70 C°, casing is assumed adiabatic at outside. Because of the relatively slow heating of the solids compared to rotor revolution, time step size of solid heating is artificially increased by a factor 10,000 in this simulation.