The vortex tube or Ranque–Hilsch vortex tube is a device that enables the separation of hot and cold air as compressed air flows tangentially into the vortex chamber through inlet nozzles. Separating cold and hot airs by using the principles of the vortex tube can be applied to industrial applications such as cooling equipment in CNC machines, refrigerators, cooling suits, heating processes, etc. The vortex tube is well-suited for these applications because it is simple, compact, light, quiet, and does not use Freon or other refrigerants (CFCs/HCFCs). It has no moving parts and does not break or wear and therefore requires little maintenance. Thus, this paper presents an overview of the phenomena occurring inside the vortex tube during the temperature/energy separation on both the counter flow and parallel flow types. The paper also reviews the experiments and the calculations presented in previous studies on temperature separation in the vortex tube. The experiment consisted of two important parameters, the first is the geometrical characteristics of the vortex tube (for example, the diameter and length of the hot and cold tubes, the diameter of the cold orifice, shape of the hot (divergent) tube, number of inlet nozzles, shape of the inlet nozzles, and shape of the cone valve. The second is focused on the thermo-physical parameters such as inlet gas pressure, cold mass fraction, moisture of inlet gas, and type of gas (air, oxygen, helium, and methane). For each parameter, the temperature separation mechanism and the flow-field inside the vortex tubes is explored by measuring the pressure, velocity, and temperature fields. The computation review is concentrated on the quantitative, theoretical, analytical, and numerical (finite volume method) aspects of the study. Although many experimental and numerical studies on the vortex tubes have been made, the physical behaviour of the flow is not fully understood due to its complexity and the lack of consistency in the experimental findings. Furthermore, several different hypotheses based on experimental, analytical, and numerical studies have been put forward to describe the thermal separation phenomenon.

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Review of Ranque–Hilsch effects in vortex tubes

A critical review of temperature separation in a vortex tube

Numerical investigation of the thermal separation in a Ranque–Hilsch vortex tube

Large eddy simulations of the flow field and temperature separation in the Ranque-Hilsch vortex tube

Numerical investigations on flow behaviour and energy separation in Ranque–Hilsch vortex tube

http://www.fem.unicamp.br/~phoenics/EM974/PROJETOS/Temas%20Projetos/VORTEX%20TUBE%20COOLING/cfd%20vortex%20tube.pdf

CFD analysis and experimental investigations towards optimizing the parameters of Ranque-Hilsch vortex tube

Publisher Summary This chapter describes the use of computational fluid dynamics (CFD) techniques to arrive at optimum design parameters of vortex tubes to fabricate them. Ranque-Hilsch vortex tubes are well known devices having no moving mechanical parts in which, compressed gas injected through tangential nozzles into a vortex chamber results in the separation of inlet flow into two streams, one of which is warmer than the inlet gas while the other is colder. Vortex tubes for mixture separation are finding increased use for drying and purification of gas mixtures as well as separation of liquid oxygen (LOX) from pre-cooled air stream. Experimental studies have shown that for a 12 mm diameter straight vortex tube with six conical nozzles, maximum temperature difference of ≈109 K between hot and cold end flows was obtained for length to diameter ratio (L/D) > 25 and with optimum cold end diameter (dc) of 7 mm. Studies of LOX separation from pre-cooled air flow show that conical vortex tube gives highest LOX purity of ≈96% and the higher separation efficiency of ≈61% compared to straight vortex tubes. Experiments were conducted to study LOX purity and separation efficiency of straight and conical vortex tubes. The maximum LOX purity of 96% was obtained for conical vortex tube along with 14% separation efficiency. A maximum of 61% separation efficiency was obtained for conical vortex tube when the LOX purity was controlled at ≈66%. Straight vortex tubes give inferior performance in LOX separation compared to conical tubes. For straight tubes, the studies show that the purity and separation efficiency are dependent on L/D ratios.

S.N. Ram

Papers

CFD analysis and experimental investigations towards optimizing the parameters of Ranque-Hilsch vortex tube

Design of vortex tubes and experimental program on LOX separation using cryogenic vortex tubes