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Experimental investigation of vortex tube concepts

University of British Columbia

The vortex tube is a very simple device which separates a compressed gas into a cold and a hot stream. The compressed gas is injected tangentially into the tube inlet by means of a nozzle. The gas develops a swirling motion in the tube. The gas leaving the tube near the wall will be warmer and that leaving the tube from the center will be cooler. Typically, with compressed air at 3 atm. and 290 K, it is possible to obtain a cold stream of T[sub]c = 260 K and a hot stream of T[sub]h = 330K. The general motivation of this thesis was to clarify the numerous assumptions on the vortex tube effect by the analysis of new measurements. Compared to previous studies, standard measurements of pressures and temperatures were improved by having the sensors very close to the tube. New measurements were obtained with the help of three novel techniques: i) Velocity profile measurements were done with a special pitot tube. ii) The vortex tube was tested at inlet pressures below atmospheric. iii) The spectrum of sound generated in the vortex tube was measured with the help of internally mounted microphones. The new data were compared to previous models, especially the two-streams model by Ahlborn et al. (1994), where the heating in the vortex tube is attributed to the conversion of kinetic energy into heat and the cooling to the reverse process. Due to the accuracy of the inlet pressure measurements, the new experiments showed unexpected high inlet velocities. In contradiction to Ahlborn's model, where the cold and hot streams have the same amount of energy, the vortex tube effect is explained in this work by an energy separation, in which the cold stream exits the tube with a lower energy than the hot stream.

Thesis/Dissertation

application/pdf

2009-01-13

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http://hdl.handle.net/2429/3608

Physics

University of British Columbia

UBCV

DSpace