Experimental study of the flow structure in a counter flow Ranque–Hilsch vortex tube

The mechanism of the temperature separation in a Ranque–Hilsch vortex tube has been investigated since the discovery of this phenomenon. In spite of being investigated by many researchers, no consensus has yet been reached regarding the mechanism’s hypothesis. This paper reports on a study in progress exploring the temperature separation in a counter-flow vortex tube. The effects of the geometrical parameters, including inlet nozzles, cold exit, hot exit and length of the tube, were investigated, which indicated the settings for the best performance of the vortex tube. Flow properties in the vortex tube were measured and used to understand the flow structure inside the tube. Accurate measurements of the three-dimensional velocity distribution in the tube were conducted. The results provided enough evidence that the flow in the tube consists of a forced vortex formed near the inlet gradually transforming to a free vortex at the hot end. Experimental results found in this research show the vortex transformation along the tube and support the hypothesis proposed in previous study.