SECONDARY FLOW IN A VORTEX TUBE

A novel Pitot probe was used to measure the axial and azimuthal veloci ties in a vortex tube. The probe has only a single measuring port and is hence smaller than standard devices. It monitors stagnation and ref erence pressure sequentially as the probe is rotated around its axis. From the measured velocity field in the 25 mm diameter vortex tube the local mass flux was determined and it was observed that the return fl ow at the center of the tube is much larger than the cold mass flow em erging out of the cold end. Therefore, the vortex tube must have a sec ondary circulation imbedded into the primary vortex, which moves fluid from the back flow core to the outer regions.