Analysis on the fluid flow in vortex tube with vortex periodical oscillation characteristics

To reveal the energy transferring mechanism in the vortex tube, which is an interesting phenomenon in the area of heat and mass transfer, numerical simulation and analysis of the dynamic fluid flow were employed. In contrast to the previous static study, the focus of this paper is the dynamic process, or the oscillation, of the secondary circulation layer. Based on the fluid flow results derived from the unsteady 3-D computation, the existence of the forced or Rankine vortex was confirmed, which also verified the certainty of reverse flow in the cold end of the vortex tube. Then, the oscillation of the boundary layer of the central recirculation zone was emphasized and the periodical vibrating of the fluid flow within the secondary circulation zone, varying of its boundary, and the typical frequencies of points on a cross section were provided. Based on these results, a novel energy transferring mechanism in the vortex tube was proposed, under the condition that stable oscillation of the boundary layer is the dominant mechanism for the heat and mass transfer process.