A Numerical Simulation of the Effect of Inlet Gas Temperature on the Energy Separation in a Vortex Tube (original) (raw)
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Thermodynamic analysis of the energy separation in a counter-flow vortex tube
The phenomenon of temperature separation within a vortex tube is a complex result of different factors, including pressure gradient, flow stagnation and mixture due to the internal flow structure, energy transfer between the different flow layers and heat transfer between the tube and the ambient air. There has not been a well accepted explanation for the phenomenon due to its complex internal flow condition. This paper reports analytical results of different expansion models, effect of different working fluids on the cooling performance and energy balance in the tube. Supports for pervious published hypothesis and recommendation for further research are concluded from these analytical results.
2017
A numerical analysis is carried out in this study in order to understand the flow field and the associated temperature separation in a Ranque-Hilsch vortex tube. A three dimensional computational fluid dynamics model, using ideal gas compressible flow assumptions, is employed to predict the performance of a vortex tube. The standard k-epsilon CFD turbulent model is adopted in this study. The study focuses on an insulated counter flow vortex tube with four tangential inlet streams, one axial hot outlet stream and one axial cold outlet stream. The study shows that one can numerically predict the behaviour of energy separation using ideal gas assumption. The numerical study shows that with an adapted vortex tube size a maximum temperature separation is achieved at optimum pressure value of 4 bar. For insulated tube, as tube length increases, the energy separation increases until it approaches an asymptote value. An optimum diameter exist where energy separation reach maximum value.
International Journal of Heat and Technology, 2013
Xue et al. [12] studied pressure gradient, viscosity and turbulence, secondary circulation, and acoustic streaming in the vortex tube. Using a three-dimensional CFD model, Shamsoddini and Hossein Nezhad [13] analyzed the flow and heat transfer mechanism in the vortex tube. In order to investigate the variation of velocity, pressure, and temperature ABSTRACT A mechanical device with no moving parts, a vortex tube can generate cold and hot gas flows from compressed gas. This paper investigates the effect of using a divergent hot tube on vortex tube refrigeration capacity. The computational fluid dynamics (CFD) model used is a three-dimensional steady compressible model utilizing the k-ɛ turbulence model. In this numerical research, different divergence angles of the hot tube (β=0°, 1°, 2°, 3°, 4°, and 6°) have been simulated to analyze the performance of the vortex tube. The results showed that as the angle diverges from β=0°, cold temperature separation improves at cold mass fractions greater than about 0.4, but increasing the angle to more than 4° impairs cold temperature separation compared with the cylindrical model because a secondary circulation develops in the vortex tube. Validation of a previous experimental study that used a cylindrical vortex tube has also been performed in this research.
3D Numerical Investigating of Flow Field and Energy Separation in Counter-flow Vortex Tube
Proceedings of the 2nd World Congress on Momentum, Heat and Mass Transfer, 2017
A numerical analysis is carried out in this study in order to understand the flow field and the associated temperature separation in a Ranque-Hilsch vortex tube. A three dimensional computational fluid dynamics model, using ideal gas compressible flow assumptions, is employed to predict the performance of a vortex tube. The standard k-epsilon CFD turbulent model is adopted in this study. The study focuses on an insulated counter flow vortex tube with four tangential inlet streams, one axial hot outlet stream and one axial cold outlet stream. The study shows that one can numerically predict the behaviour of energy separation using ideal gas assumption. The numerical study shows that with an adapted vortex tube size a maximum temperature separation is achieved at optimum pressure value of 4 bar. For insulated tube, as tube length increases, the energy separation increases until it approaches an asymptote value. An optimum diameter exist where energy separation reach maximum value.
NUMERICAL SIMULATION OF TEMPERATURE SEPARATION PHENOMENA INSIDE VORTEX TUBE
The objective of present article is an atempt to simulate numerically temperature separation phenomena (Ranque-Hilsch affect) inside the vortex tube. For this simulation computational fluide dynamic (CFD) analysis, applying standard k-ε turbulence model, is used. Geometry is drawn in 3D space using Autodesk Inventor Professional and transferred in Autodesk Simulation CFD to solve the problem. Initial conditions for inlet air stream: temperature 22ºC, flow rate 40l/min and gauge pressure 6 bar are set. As a result air flow velosity field and temperature field is found. Predicted temperatures at cold and hot end are 4 and 42ºC. It can be concluded that vortex tube can be analysed and further optimisated by CFD modeling.
A Review of Computational Studies of Temperature Separation Mechanism in Vortex Tube
Bonfring
The Ranque Hilsch Vortex Tube (RHVT) is a very simple device well known for its phenomenal temperature separation effect. With a single input of compressed gas, the tube simultaneously produces two different streams of gas ? one being hotter and other being colder than input gas. Over the years, different theories have attempted to explain this effect without achieving any universal agreement. Small size of RHVT presents considerable difficulties towards predicting temperature, pressure and flow field inside it. This is where Computational Fluid Dynamics (CFD) analysis comes to the aid of researchers. Many of researchers have attempted such analysis using turbulence models such as The Standard k-ε model, RNG k-ε model & Realizable k-ε model, Large Eddy Simulation Technique (LES) etc. This paper attempts to present a review of such recent qualitative studies carried out on RHVT using CFD. Care has been taken to explore diversified parameters related to flow physics inside RHVT, instead of being monotonous one. This review is expected to help future researches in the related domain
Flow behavior and thermal separation mechanism on vortex tube
Journal of Thermal Engineering, 2021
Flow behaviour and thermal separation mechanism on vortex tubes have been studied numerically. Rapid expansion indicated by high-pressure gradient near the inlet and the exit ports contributes to energy separation on the parallel and the counter flow vortex tubes. It creates a cooling process at the core region and drives an internal and rotational energy transfer to the peripheral region, then increases the gas temperature at the periphery along with friction due to the presence of the confined wall. Static temperature is related to static pressure in such a way that low pressure leads to the low static temperature at the same region inside the vortex tube. On the other hand, the high total temperature is found in the region with the low dynamic velocity. For both vortex tubes, the flow fields are mainly governed by the tangential velocity at the periphery and by the axial velocity at the core region. The maximum Mach number values based on the maximum tangential velocities in the inlet area for the counter and the parallel flow vortex tubes are 0.689 and 0.726, respectively, so both are compressible and subsonic flows. For the same size of geometry and boundary conditions, the parallel flow vortex tube has higher COP than the counter flow vortex tube i.e. 0.26 and 0.25, respectively.
Effects of variable thermophysical properties on flow and energy separation in a vortex tube
International Journal of Refrigeration, 2013
The present paper considers the numerical simulation and exergy analysis of a vortex tube with temperature-dependent thermophysical properties of air selected as the working fluid. A 3D computational domain has been generated considering the quarter of the geometry and assuming periodicity in the azimuthal direction which was found to exhibit correctly the general behaviour expected from a vortex tube. First, flow and heat transfer within the vortex tube have been determined by solving the conservation equations of continuity, momentum and energy using the second moment closure model (RSM) to model the turbulence effects. Results allow to obtain the flow and heat transfer behaviours within the tube and to compute mean pressures and temperatures at the cold and hot ends. These parameters are used in the exergy analysis to quantify the exergy losses produced within the vortex tube and its exergy efficiency. The models results are compared to experimental data obtained from the literature. Four cases have been considered by changing the inlet air pressure from 200 up to 380 kPa. It has been observed that RSM model is not only capable of predicting fairly well the general flow features but also it is capable of matching correctly the measured cold and hot outlet temperatures.
Scientia Iranica, 2016
The vortex tube air separator is an invaluable tool which has the ability to separate a high-pressure uid into the cold and hot uid streams. The hot tube is the main part of the vortex tube, along which the energy separation procedure happens. This research has been done to analyze the e ect of the convergent angle and cold ori ce diameter on thermal e ciency of a convergent vortex tube. The convergent hot tube angle varies over the range of 1 to 9 deg. Attention to the main angle e ect denotes that the highest thermal ability could be achieved at = 5 deg. Experiments denote that both cooling capability and heating e ectiveness reach the highest magnitudes when D Cold is around 9 mm. After these two stages, the optimized convergent vortex tube is capable of decreasing and rising air temperatures at the cold and the hot sides up to 9.05 K (42.89%) and 10.48 K (44.74%), respectively. A computational uid dynamics model is employed to predict the performance of the convergent vortex tube. The numerical investigation is done by full 3D steady-state CFD-simulation using FLUENT6.3.26. The results show that the agreement between computation predictions and laboratory measurements is fairly good.
Scientia Iranica, 2013
In this numerical study, energy separation analysis of a Ranque-Hilsch vortex tube (RHVT) has been investigated for different conditions such as operation of machine under applying different inlet gases. The utilized gases in this study are nitrogen dioxide (NO2), carbon dioxide (CO2), oxygen (O2), nitrogen (N2) and air. The cooling and heating performance in a commercial vortex tube for the mentioned gases has been described in details and illustrated by different curves. The present three-dimensional (3D) computational fluid dynamic (CFD) model is a steady axisymmetric model that employs standard k-e turbulence model to perform the computation procedure of results. Various key parameters including cold and hot exit temperature differences and energy separation rates are described numerically. The results show that NO2 enhances the greatest amount of cooling and heating capacity among investigated gases. Some of numerical results are validated by available experimental data. Furthe...