Counter-flow Vortex Tube Research Articles

Computational study for the cooling performance and effect of insulation on the vortex tube with different insulating material

The purpose of the current study is to explain the thermal performance of a counterflow vortex tube considering air as a working fluid and with different insulating materials such as fiberglass, cotton wool, nitrile rubber sheet and polyurethane for a steady-state, turbulent flow, axisymmetric, 3-D, compressible flow vortex tube with computational fluid dynamics. In the present investigation, the cooling power performance, coefficient of performance, and isentropic efficiency have been analyzed for insulating and non-insulating vortex tubes. The standard k-ɛ model with various intake pressure and mass fractions was used in the ANSYS FLUENT application for the numerical analysis, and outcomes were validated with experimental results. The conclusion drawn with simulation is that by considering insulation with polyurethane along the hot tube and working fluid as air, the performance of the vortex tube has increased by 9.867% when compared with the vortex tube without insulation.

Reducing Energy Consumption and CO2 Emissions in Natural Gas Preheating Stations Using Vortex Tubes

This work proposes an innovative method for adjusting the natural gas from the grid to the consumer pipeline requirements in a full-scale pressure reduction station. The use of two counterflow vortex tubes instead of the traditional boiler to preheat the gas before throttling is demonstrated as a powerful alternative. Thus, a reduction of fossil fuel consumption is reached, which amounts to 7.1% less CO2 emitted. To ensure the optimal configuration, the vortex tube was thoroughly characterized in laboratory facilities using nitrogen as the working fluid. Various operating conditions were tested to determine the most efficient setup. Computational Fluid Dynamics (CFD) simulations were conducted with nitrogen to validate the behavior of the vortex tube. Subsequently, the working fluid was switched to methane to assess the performance differences between the two gases. Finally, the vortex tubes were deployed at a full-scale installation and tested under real consumption demand. The results obtained from this study offer promising insights into the practical implementation of the proposed method for adjusting the natural gas flow, highlighting its potential for reducing fossil fuel consumption and minimizing CO2 emissions. Further improvements and refinements can be made based on these findings.

Numerical Analysis of Temperature Separation and Exergy Analysis of a Dual-Inlet Section Convergent Vortex Tube

Abstract The present study deals with the optimization of a counter flow vortex tube with a straight single intake section, straight dual intake section, and convergent dual intake section vortex tube model for different physical and flow parameters. The effect of variation of convergent angles (θ), intake pressures, and a number of inlet sections on the flow separation has been analyzed in the present study. ANSYS FLUENT software has been used to simulate flow considering air as a working fluid. Moreover, some physical and flow parameters such as intake pressure, cold temperature gradient (ΔTc), pressure loss ratio, cold mass fraction, and hot temperature gradient (ΔTh) have been studied to optimize the vortex tube. The coefficient of performance has been compared for various convergent angles from 1 deg to 5 deg. The result has been validated by the experimental and numerical studies performed previously. Moreover, the exergy analysis has also been conducted for the convergent dual intake vortex tube for various convergent angles, cold mass fraction, and intake pressure. The study concludes that the convergent vortex tube having a dual inlet section, 5-deg angle shows the optimized result for all the mass fraction and intake pressure, compared to a straight single intake section and straight dual intake vortex tube.

Numerical Study of the L/D Ratio and Turbulent Prandtl Number Effect on Energy Separation in a Counter-Flow Vortex Tube

Vortex tube is a device without moving parts with ability to separate pressurized gas into two streams: cold and hot. This is a consequence of the Eckert-Wiese effect, which is responsible for spontaneous redistribution of total energy within the flow domain. In order for vortex tubes to work properly, there are some constraints which have to be fulfilled. The most important constraint in that sense is the L/D ratio. One part of this paper is dedicated to the research of the influence of L/D ratio on the energy separation in a vortex tube, i.e. to the values of total temperatures on cold and hot outlets of the device. On the other hand, experimental research of the inner flow is quite challenging since vortex tube is a device of small dimensions. Hence, we are relaying on numerical computations. One of important quantities that has to be prescribed in these computations is the turbulent Prandtl number PrT. Because of that, the other part of this paper is dedicated to research of the influence of PrT on the results of numerical computations. The research is conducted using open-source software OpenFOAM. Turbulence is modelled using two-equation and RST models. For small L/D ratios there is a secondary circulation that acts as a refrigeration cycle, and for greater L/D ratios distribution of velocity and temperature inside the vortex tube remains the same, regardless of the stagnation point presence. It is not justified to increase the length of the vortex tube beyond 20D since the change in cold total temperature inside the vortex tube as well at the cold outlet is practically null. For L/D variation from 1.8 to 10, the cold outlet temperature changes from 270.9 K to 266.8 K, and then rises to its final value of 270.5 K. For L/D ratio from 20 to 60, the total temperature at cold end remains unchanged at 271.3 K. We obtained good results with the unit value of turbulent Prandtl number, and demonstrated that increasing the PrT beyond unit value is not necessary in order to numerically obtain the energy separation inside the vortex tube.

Application of mixed level design of Taguchi method to counter flow vortex tube

A Vortex Tube (VT) creates instant separate hot and cold streams from an input stream of compressed air. However, the output of VT depends on numerous operating and geometric characteristics. Further, experimentation using all combinations of conditions is rather unrealistic, both physically and financially. Hence, a primary evaluation of VT becomes important using principles of Design of Experiments.This research work presents methodology and results of a statistical assessment of VT’s temperature separation effect through Taguchi method. This method is beneficial because it requires lesser number of trials. Present study uses L16 orthogonal array to perform the experiments for different conditions of pressure at entry to VT, cold mass fraction (µc) and insulation. Distinctiveness of this analysis is that statistical analysis of VT has been presented using Mixed Taguchi Design. This method represents different number of levels for control factors, unlike other designs. Lastly, confirmation experiment authenticates the usefulness of Taguchi method to predict VT’s performance with adequate accuracy. Results specify that experimental efforts are reduced by 62.96% using Taguchi method.

Influence of a double vortex chamber on temperature reduction in a counter-flow vortex tube

This article reports the effect of double vortex-chambers with multiple inlet snail entries of N = 1, 4 and 6 nozzles on the energy separation referred to cold gas exit temperature difference (ΔTc) in a counter-flow vortex tube type. The experimental work focused on ascertaining the effects of entry air pressure (Pi = 2, 3 and 4 bar), distance ratios between the two vortex-chamber to the vortex tube diameter (l/D = 0.875–1.125) and the cold gas mass ratio (μc) in a vortex tube. It was found that cold gas exit temperature difference (ΔTc) increased with increasing inlet air pressure (Pi) and number of inlet nozzles (N), and decreasing l/D. Among the studied conditions, the double vortex-chamber operated at the highest Pi of 4 bar, N = 6, the smallest l/D = 0.875 and μc = 0.38 gave the highest cold gas exit temperature difference (ΔTc) of 31.5 °C. In addition, the deep learning optimization technique was also developed to predict the temperatures for different combination of parameters used in this study. It was found that the optimal models provide maximum R2 value of 0.99317.

Numerical study of a double inlet chamber counter flow vortex tube with insulation

The present study intends to improve the performance of the Ranque-Hilsch counter flow vortex tube, analysed using computational fluid dynamics. In the axisymmetric 3-D, steady-state, compressible, and turbulent flow vortex tube, the air has been used as the working fluid. The ANSYS17.1 FLUENT software has been used with the standard º-ε turbulent model for different mass fraction of cold fluid and inlet pressure in the numerical simulation and validated with the experimental results. It is observed from the study that as the inlet chambers number increases from 1 to 2, there is a decrease of 7.8 % in the cold exit temperature of the vortex tube. However, insulating the double chamber vortex tube leads to a further reduction of 4.2% in the cold exit temperature. Therefore, it indicates that the overall decline in the cold exit temperature from one chamber non-insulated vortex tube to double chamber insulated vortex tube is 9.6%. In terms of cold exit temperature, it can be concluded that using a double inlet chamber vortex tube with insulation yields the optimum results.

Flow behavior and thermal separation mechanism on vortex tube

Flow behaviour and thermal separation mechanism on vortex tubes have been studied numer-ically. 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.

Experimental study and CFD analysis of energy separation in a counter flow vortex tube

In this manuscript, both experimental and numerical investigations have been carried out to study the mechanism of separation energy and flow phenomena in the counter flow vortex tube. This manuscript presents a complete comparison between the experimental investigation and CFD analysis. The experimental model was manufactured with (total length of 104 mm and the inner diameter of 8 mm, and made of cast iron) tested under different inlet pressures (4, 5, and 6 bar). The thermal performance has been studied for hot and cold outlet temperature as a function of mass fraction, ?, (0.3---40.8). The 3-D numerical modeling using the k-? model used with code (FLUENT 6.3.26). Two types of velocity components are studied (axial and swirl). The results show any increase in bot-h cold mass fraction and inlet pressure caused to increase ?Tc, and the maximum ?Tc value occurs at P = 6 bar. The COP of two important factors in the vortex tube which are a heat pump and a refrigerator have been evaluated, which ranged from 0.25 to 0.74. A different axial location (Z/L = 0.2, 0.5, and 0.8) was modeled to evaluate swirl velocity and radial profiles, where the swirl velocity has the highest value. The maximum axial velocity is 93, where it occurs at the tube axis close to the inlet exit (Z/L = 0.2). The results showed a good agreement for experimental and numerical analysis.

Temperature separation characteristics of CH4–CO2 binary gas mixture within a vortex tube

In the natural gas industry, sour gas usually contains some impurities such as CO2. The influence of CO2 fraction on temperature separation within the vortex tube is not fully understood. In the present work, a simulation study has been conducted to investigate the flow and heat transfer behavior of CH4–CO2 binary gas mixtures in a counter flow vortex tube. The model was validated against the experimental data and the predicted temperature separation is found to satisfactorily accord with the experimental values. The mole fraction of CO2 is varied in the range of 0–1.0. The temperature and velocity distribution characteristics of the gas mixture with various CO2 mole fractions are obtained. The results show that velocity and temperature separation increase with increase of mole fraction of CH4 at given inlet flow rate. According to the streamline structure, the area of the backflow region grows as the CH4 mole fraction increases. But the coefficient of performance tends to decrease with improving CH4 content.

Review of vortex tube: a sustainable and energy separation device for multi-purpose applications

ABSTRACT A vortex tube is a device, which uses pressurised inlet gas to split into hot and cold separate streams. This phenomenon is referred to as energy separation. The literature behind the energy separation in vortex tube is huge as the device was invented in 1933. The improvement in the performance of the device and the working principle behind the energy separation has been the topic of interest to many researchers around the globe. However, the ability to produce hot/cold gases without mechanical device finds promising applications in literature. This review article recommends the usage of vortex tube to many diverse fields of applications. The operational parameters involved in every application are tabulated and studied. The collection of articles on counter-flow vortex tube oriented towards the application provide the reader a fascinating choice in recovering energy from pressurised gas and ability to meet certain applications required in a particular industry.

Experimental investigation on heating performance of a counter-flow vortex tube

ABSTRACT Previous researches mainly focused on the cooling performance of the vortex tube. Here, the heating performance indicators such as hot temperature difference, heating rate per unit air, and coefficient of performance are investigated experimentally. The results show that the maximum heating separation is obtained when the cold mass fraction is in the range of 0.45–0.7. The influence of inlet pressure on the hot temperature difference tends to reduce when it exceeds 0.3 MPa. Increase of the inlet pressure will cause the decrease of heating rate. Compared with 4-nozzle vortex tube, much better performance is achieved when 6-nozzle vortex tube is used.

Exergy analysis of the flow process and exergetic optimization of counterflow vortex tubes working with air

Vortex tubes can separate a pressurized gas stream into a cold stream and a hot stream. However, their use is limited by the low efficiency of the device. In this article, the exergy efficiency considering transiting exergy is used to analyze the thermal exergy production and exergy destruction in vortex tubes using a thermodynamic model and experimental data from the literature. The vortex tube exergetic efficiency reaches a maximum (up to 2.88%) for a cold mass fraction around 0.7 when both the hot and the cold outlets are considered as useful. Interestingly, 45% of the available exergy is lost downstream of the vortex tube through pressure losses at this condition. Inside the vortex tube, kinetic exergy destruction represents a great portion of the irreversibilities within the tube. Furthermore, the thermodynamic model is used to maximize the efficiency of a single vortex tube. The optimization process increases the exergetic efficiency of the vortex tube to 4.4%, corresponding to an increase of 53% compared to the best experimental values. Additionally, the analysis demonstrates that increasing the cold outlet pressure increases the vortex tube exergetic efficiency for the same pressure ratio. Finally, the thermodynamic model is used to identify the vortex tubes cascade which better uses a compressed air source at 6 bars. A cold cascade with an ejector is also investigated. Results show that the cascade configuration could benefit from unused pressure from the first tube to increase the system exergetic efficiency.

PERFORMANCE OPTIMIZATION OF PARALLEL CONNECTED RANQUE-HILSCH VORTEX TUBES WITH CARBON DIOXIDE AND AIR USING THE TAGUCHI METHOD

In this study, the influence of the parameters affecting the vortex tube performance was investigated using the Taguchi method for a system of parallel connected Ranque-Hilsch vortex tubes (RHVT) comprising two counterflow vortex tubes. The RHVT performance parameter is the temperature difference (ΔT) between the hot flow outlet and the cold flow outlet of the RHVT. For this study, the parameters called control factors are four as vortex tube inlet pressure, working fluid type, number of nozzles, and nozzle material. Two and six nozzles made of polyamide and brass were used and CO2 and air were used as a working fluid. The quantity ΔT was optimized according to the Taguchi L16 orthogonal array test design for eight levels of RHVT system inlet pressure in the range of 150-500 kPa with the specified parameters and levels. Control experiments were performed, and optimization results were obtained. The most important control factor affecting the performance of parallel connected RHVT system was determined as a working fluid inlet pressure according to the Taguchi method, and the percentage effect of it was calculated as 74.85%. The effectiveness of nozzle number, nozzle material, and working fluid type parameters are the factors following the inlet pressure, respectively.

Effect of number of the nozzle and cold mass fraction on the performance of counter flow vortex tube using the computational fluid dynamic analysis

ABSTRACT The vortex tube or Ranque–Hilsch vortex tube is a device that separates cold and hot air from compressed air while entering into the vortex chamber through the tangential inlet nozzles. A three-dimensional CFD model has been developed to study the flow behaviour of a vortex tube. The standard k–ϵ model has been used to model the turbulent flow inside the tube. The vortex tube of L/D ratio of 10 with different number of nozzles was analysed. The inlet pressure is varied from 2 bar to 6 bar with a constant inlet temperature of 303 K at different positions of the conical valve. The results of the present CFD study are in good agreement with the experimental results.

Thermodynamic modeling and artificial neural network of air counterflow vortex tubes

A large number of operational and geometrical parameters are involved in the optimization of counterflow vortex tubes. The number of parameters is so important that most researchers relied on a one factor at a time approach which cannot capture the possible interactions between the relevant parameters. Additionally, literature contains very few information on how to design properly a vortex tube for given inlet conditions.To identify the most important features, two approaches are used: artificial neural networks (ANNs) and thermodynamic modeling. Both methods could reproduce accurately the cold outlet temperature of vortex tubes from the literature. To achieve this, the ANN uses only the inlet pressure, the cold mass fraction, the length to the diameter ratio and the cold outlet diameter to the vortex diameter ratio. The output from another ANN is the inlet mass flow rate. This second ANN uses only the inlet pressure, the length to diameter ratio, the total inlet nozzles’ area and the vortex tube diameter as inputs to do the calculation.The most important parameter in the thermodynamic model is the inlet pressure to cold outlet pressure ratio. It is shown that the variations of this ratio by friction in the inlet nozzles are not negligible and should be considered in future vortex tubes’ design. The Bödewadt boundary layer flow between the inlet and the cold outlet affects also significantly the vortex tube performance.

Numerical investigation of vortex tubes with extended vortex chambers

Ranque–Hilsch vortex tubes are often utilized to produce cooling when a compressed air source is readily available. In comparison with traditional cooling technologies, vortex-tube devices are much simpler, since they do not have moving parts. However, their thermal efficiencies are also lower, so they are used primarily for industrial spot cooling. Several options to modify and improve vortex tube performance exist. While a lot of previous research efforts addressed optimization of the inlet and outlet components, the main tube variations have not been thoroughly explored beyond simple tapered tubes. In this paper we numerically investigate augmenting vortex tubes with cyclonic-type extensions of the vortex chambers. The computational fluid dynamics software STAR-CCM+ was utilized to simulate a typical counter-flow vortex tube operating with air. The numerical approach was validated via comparison to experimental studies available in the literature. A reasonably efficient high-capacity vortex tube design was parametrically analyzed. This setup and its several modifications were numerically modeled under selected external conditions. The configuration with an intermediate-size vortex chamber extension demonstrated the highest performance among the studied setups. This variant of the vortex tube was also predicted to perform better than the original system by about 15% in a range of cold-flow fractions.

Influence of the channel length of a vortex tube on the air temperature separation

A model of a counterflow vortex tube has been prepared to study the dependence of the influence of the tube length parameter on the cold and hot air production. Computational experiments were made using the OpenFOAM package. The prepared grid allowed us to carry out simulations for vortex tubes with lengths of the main channel varying from 20 to 70 cm. All calculations were performed with boundary conditions with constant inlet pressure and atmospheric pressure at the outlet. Results were obtained on temperatures and mass flow rates of the air in the cold and hot outlets of the vortex tube, depending on the length of the device. It is shown that an increase of the length of the vortex tube channel increases the production of cold air. An increase in the temperature of the produced hot air on vortex tube length increase was also noted.

The influence of the vortex tube channel length on the separation of air by its temperature

Based on the prepared counterflow vortex tube model with four inlets, the effect of the length of the vortex tube channel on the generation of cold and hot air is investigated. In the simulation were used standard equations of gas dynamics, which include the equations of continuity, conservation of momentum, total energy, and the state of an ideal gas. To consider turbulent effects was chosen a -\varepsilon$ turbulence model. Computational experiments were carried out in the OpenFOAM software using the sonicFoam solver. The prepared grid allowed modeling vortex tubes with the main channel length varying from 20 to 70 cm. All calculations were carried out under the same boundary conditions with constant pressure at the inlets and atmospheric pressure at the hot and cold outlets. The constructed model adequately reproduces the two-vortex structure of the air flow in the vortex tube. To obtain and process the results were used OpenFOAM utilities and a script implementing the algorithm for averaging the values at the tube outlets written in Python. The results were obtained on the temperatures and mass flow rates of air in cold and hot outlets of the vortex tube depending on the length of the device. According to the analysis of the obtained data, it was shown that increasing the length of the channel of the vortex tube significantly increases the production of cold air with a certain increase in its temperature. An increase in the temperature of the produced hot air with an increase in the length of the vortex tube was also noted.

Vortex tube modelling: outlet parameter dependencies of cold air production

A model of a counterflow vortex tube has been prepared to study the dependence of the influence of the parameters of cold and hot outlets on the production of cold air. For a fixed geometry of the vortex tube, a simulation is performed with an independent change of the length of the cold outlet nozzle, the angle of the widening of the cold outlet nozzle, and the hot outlet area. In a series of experiments, the pressure of air supplied to the inlet varies in order to take into account the possible effects of computational and model errors. An anomalous increase in the temperature of the outgoing air was observed with a hot outlet area of ∼30 cm2. Conclusions were drawn about the range of reasonable values of the outlet parameters for the considered configuration of the vortex tube.