Flow Vortex Tube Research Articles

An Experimental and Computational Investigation of Ranque–Hilsch Vortex Tube Heat Transfer Characteristics

Abstract Ranque–Hilsch vortex tubes have the extraordinary ability to split an incoming stream of fluid into two streams—one with a lower absolute total temperature than the incoming flow and the other with greater total temperature. The physical mechanism involves inducing an intense swirl of the flow down the length of the tube. The warmer flow exits around the periphery at the end of the tube, while the cooler central flow changes direction within the core and exits the opposite end. While much research has focused on the physical mechanisms of the energy separation, relatively little attention has been paid to the heat transfer behavior should a heat flux be applied to the walls. In the present work, experiments were performed using a vortex tube with air and varying levels of heat addition, up to approximately 15 kW/m2. Companion computational experiments were performed that allowed the determination of axially resolved Nusselt number distributions, the first of their kind for vortex tube flows. A notable finding is that the vast majority of heat added to the vortex tube flow remains within the hot stream; i.e., the cold stream experiences relatively little temperature rise due to the heat addition. For example, even when only 30% of the flow exits the hot side of the tube, it retains more than 80% of the heat added to the flow. Additionally, a modified swirl number was also defined that was found to scale the Nusselt number augmentation across the two different total flowrates examined presently.

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.

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.

Simple model for flow field division and flow structure calculation in a vortex tube

The flow pattern and energy transfer process in the vortex tube are extremely complex, resulting in the difficulty of the direct calculation and prediction of the flow structure and temperature separation performance of a vortex tube. In view of this, research idea of dividing the vortex tube flow field into six regions was proposed, corresponding simplifications were made in different regions according to the flow features, and fluid parameters were coupled at the boundaries. An equation for the axial velocity component in the hot tube region was developed based on the characteristic that the axial velocity profiles under different conditions present similar patterns, the calculation method of reverse flow boundary which separates the working fluid into hot and cold fluids was described, and a set of relatively simple calculation methods for the internal flow field of vortex tubes was established based on the partition model. Three-dimensional velocity distributions inside the vortex tube under different working conditions were computed and analyzed. Further, the model was evaluated and validated through experimental data. The results showed good agreements of calculated data and experimental velocity fields. This work proposed a convenient calculation method for the estimation of the flow behavior inside a vortex tube and provide reliable predictions.

Computational study for the optimization of Ranque-Hilsch vortex tube with the variation of number of inlet chamber and distance between the chambers

The purpose of the present study is to analyse the improvement in the performance of vortex tubes numerically. The air is taken as the working fluid in the compressible, axisymmetric 3-D, turbulent flow, and steady-state vortex tube. The standard k-ɛ turbulent model has been used for flow simulation in ANSYS FLUENT software with different pressure at the inlet and validated with experimental outcomes. It is found that there is an increment of 9.09 % in the cold temperature gradient with three inlet chambers as compared to single chamber. When inlet chamber numbers change from three to four, a decrease in the cold temperature gradient is recorded. When the distance between the inlet chamber increases from 8 mm to 32 mm, there is a decrease in the vortex tube’s cold temperature gradient. Therefore, it indicates that the optimum number of inlet chambers to obtain maximum cold temperature gradient, i.e., minimum cold exit temperature for the given specification of the vortex tube essential to have three inlet chambers, and the optimum distance between the inlet chambers 8 mm, is recommended.

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.

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.

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.

The dependence of the Ranque–Hilsch effect on the cold outlet geometry

The effect of such parameters of the cold outlet nozzle of the counter flow vortex tube as the length and widening angle on temperature separation is investigated. Mathematical model of gas dynamics is written with viscosity component. Computational simulation is performed in the OpenFOAM package, using the sonicFoam solver. It is shown that the temperature of the exhaust air decreases along the cold exit nozzle. The presence of the angle of widening of the nozzle affects the amount of cooling, but is not the root cause of the effect. The nonmonotonic dependence of the temperature of the exhaust gas on the length of the cold exit nozzle is demonstrated. When studying the effect on the temperature of the widening angle of a cold-exit nozzle at a fixed length, it was shown that at a fixed volume flow rate, a pronounced non-monotonic dependence is observed, while at a constant pressure drop, there is no non-monotony down to the maximum considered angle.

Energy separation in transient and steady-state flow across the cylinder

Energy separation is a spontaneous energy redistribution within a fluid flow. As a consequence, there are places with higher and lower values of total temperature in the fluid flow. It is characteristic for many flow geometries. This paper deals with the energy separation in a cylinder wake. Two flow conditions are being considered-transient and steady-state flow in the wake. Two different solvers from the open source package OpenFOAM are used in order to capture the phenomenon of energy separation. One of these solvers is modified for the purpose of calculation in a particular case of the vortex street flow. The energy equation based on the internal energy present in this solver is replaced by the energy equation written in the form of a total enthalpy. The other solver has been previously tested in the vortex tube flow, and can also capture the energy separation in the steady-state wake flow of the cylinder. In both cylinder wake flow conditions, a two-dimensional computational domain is used. Standard ?? ? ?? model is used for computations. It is proved that OpenFOAM is capable of capturing the energy separation phenomenon in a proper way in both of the wake flow cases. Good agreement between the experimental results and the ones from computations is obtained in the case of steady-state flow in the wake. Previous research findings are also confirmed in the case of vortex street flow.

Analysis of corrosion resistance when turning martensitic stainless steel X20Cr13 under chilled air-cooling

Amongst different methods of cooling in machining, application of air is con-sidered to be the cleanest and most environmentally friendly one. The aim of this paper was to explore the possibility of chilled air-cooling considering the corrosion resistance when turning martensitic stainless steel X20Cr13. Thus, a comparison between an alternative cooling technique where compressed air is refrigerated and jetted to the cutting zone by means of Ranque-Hilsch counter- flow vortex tube and the conventional flood cooling with oil-in-water emulsion was done. The corrosion resistance was determined by electro- chemical testing and the surface condition was analysed with both Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS). From the results presented herein, it can be concluded that the specimen cooled with chilled air has better resistance to corrosion activity after a cer-tain longer time in relation to the specimen cooled with emulsion. In addition, the specimen cooled with chilled air has lower surface roughness, which has a positive effect on the corrosion resistance. Hence, in the scope of environmentally friendly machining the vortex tube based chilled air-cooling can be successfully applied when turning difficult-to-cut martensitic stainless steel.

Analysis on the fluid flow in vortex tube with vortex periodical oscillation characteristics

To reveal the energy transferring mechanism in the vortex tube, which is an interesting phenomenon in the area of heat and mass transfer, numerical simulation and analysis of the dynamic fluid flow were employed. In contrast to the previous static study, the focus of this paper is the dynamic process, or the oscillation, of the secondary circulation layer. Based on the fluid flow results derived from the unsteady 3-D computation, the existence of the forced or Rankine vortex was confirmed, which also verified the certainty of reverse flow in the cold end of the vortex tube. Then, the oscillation of the boundary layer of the central recirculation zone was emphasized and the periodical vibrating of the fluid flow within the secondary circulation zone, varying of its boundary, and the typical frequencies of points on a cross section were provided. Based on these results, a novel energy transferring mechanism in the vortex tube was proposed, under the condition that stable oscillation of the boundary layer is the dominant mechanism for the heat and mass transfer process.

Experimental and 3D CFD investigation on heat transfer and energy separation inside a counter flow vortex tube using different shapes of hot control valves

The thermal separation inside a vortex tube can be influenced using different shapes of throttle valves. Experimental and numerical tests are performed on the thermal characteristics of a vortex tube equipped with four types of hot valves, namely; spherical, plate, cone and truncated cone. This research focuses on a special shape of control valve which is named spherical. The effects of injection pressure, slots number, stagnation point location and level of turbulence are analyzed for a vortex tube with the spherical valve. The results show that cooling capability can reaches the maximum value by decreasing distance between the stagnation point and the control valve, as much as possible. Also, in the case of spherical, increasing the injection pressure has different effect on cooling ability compared to other valves. Furthermore, cooling capability can be assumed approximately independent of the slots number in the case of spherical, while, cooling capability depends extremely on the slots number in the case of truncated cone. A 3D-CFD model is developed to analyze the fluid treatment using the RSM turbulence model. The comparison between the computed and the laboratory outputs presents a favorable agreement with the maximum and minimum relative differences of 6.7% and 1.5%, respectively.

Computational Fluid Dynamic Simulation of Single and Two-Phase Vortex Flow—A Comparison of Flow Field and Energy Separation

In the present work, a computational fluid dynamic (CFD) simulation has been performed to investigate single and two-phase vortex tube. Air in compressed form and partially condensed phase are used as working fluid, respectively. Simulation has been carried out using commercial CFD software package fluent 6.3.26. A detailed study has been performed to generate the profiles of velocity, pressure, and pathlines. These profiles provide an insight on how the process of energy separation as well as the flow field in the vortex tube gets affected on introduction of a liquid phase. The result shows that in case of cryogenic vortex tube, the flow reversal takes place closer to wall due to presence of a very thin wall adhering liquid film, while, in single-phase flow vortex tube, flow reversal is observed at the central portion. The model also predicts that presence of recirculation zone near warm end diminishes the refrigeration effect of vortex tube for two-phase flow.

Numerical Analysis of a Vortex Tube: A Review

Ranque–Hilsch vortex tube is a simple devise with no moving parts which could generate cold and hot air/gas streams simultaneously with compressed air/gas as a working fluid. The energy and flow separation in a vortex tube is highly depends on factors like nozzle shape, nozzle number, diameter and length of the vortex tube, inlet pressure, control valve, diaphragm hole size and cold mass fraction. As the energy separation and flow patterns in a vortex tube are highly complex and were not explained successfully by any researcher, a computational study of vortex tube flow and energy separation will give a better understanding about the physics and mechanism involved. Many researchers conducted computational fluid dynamic analysis of the vortex to have a deep insight about the process of flow separation. In this paper computational analysis of vortex by many researchers were presented along with the results obtained and suggestions to improve the performance of the vortex tube. Researchers considered Turbulence models which predict the performance precisely were discussed in the present paper. Researchers considered turbulence models like LES, k–e, k–ω and RMS to predict the energy separation in vortex tube. Some researchers considered artificial neural networks (ANN) and Taguchi methods for their analysis. Comparison of the predictions with simulation results were also presented to give a clear idea for the reader about the CFD models prediction capabilities.

System of High-performance Cutting with Enhanced Combined Effect of Cooling and Lubrication Medium Based on Ranque-hilsch Effect

Presents the results of the study of the main factors for improvement of the efficiency of high-performance cutting of structural steels. It has been revealed that such improvement should be implemented on the basis of simultaneous enhancement of cooling and lubrication medium (CLM). It is shown that the standard methods of supplying CLM to cutting area or use of air ionized by corona discharge as process medium are not able to effectively cool cutting area during blade cutting because of balance of endothermic and exothermic reactions. The study has considered the possibility of enhancement of CLM on the basis of Ranque-Hilsch Effect, the use of which during cooling of air flow in vortex tube allows overcoming the dew point, resulting thereby in intense air humidification and substantial enhancement of lubricating effect of process medium. It has been found out that cumulative effect of efficient cooling and enhancement of lubricity of ionized air process medium contributes to improvement of the basic characteristics of cutting process, improves tool life and significantly increases the efficiency of high-performance cutting.

Modeling the cooling performance of vortex tube using a genetic algorithm-based artificial neural network

In this study, artificial neural networks (ANNs) have been used to model the effects of four important parameters consist of the ratio of the length to diameter(L/D), the ratio of the cold outlet diameter to the tube diameter(d/D), inlet pressure(P), and cold mass fraction (Y) on the cooling performance of counter flow vortex tube. In this approach, experimental data have been used to train and validate the neural network model with MATLAB software. Also, genetic algorithm (GA) has been used to find the optimal network architecture. In this model, temperature drop at the cold outlet has been considered as the cooling performance of the vortex tube. Based on experimental data, cooling performance of the vortex tube has been predicted by four inlet parameters (L/D, d/D, P, Y). The results of this study indicate that the genetic algorithm-based artificial neural network model is capable of predicting the cooling performance of vortex tube in a wide operating range and with satisfactory precision.