A heat transfer relation for swirl flow in a vortex tube

An experimental investigation was made to study the heat transfer behavior of a water-cooled vortex tube with air as the working medium. The vortex flow was generated by leading the compressed air to enter the vortex tube tangentially. The pressures of the inlet air were 300 to 500 kPa gauge. For each of these inlet pressures, the heat transfer performance of the vortex tube was studied at different cold mass flow ratios. New experimental data are presented. An empirical correlation for the prediction of the air-side Nusselt number is established. It was shown that the air-side Nusselt number for the swirl flow in this vortex tube can be up to 30 times higher than that for a flow without swirl in the same tube.