Energy Separation In Vortex Tube Research Articles

Quantitative analysis of energy transfer and separation in vortex tubes: Factors and empirical insights

As a device with a simple structure for energy separation, the low efficiency of the vortex tube is the primary obstacle hindering its widespread application. No existing energy separation theory has gained wide acceptance due to inconsistencies with actual processes. Therefore, drawing on prior studies concerning the flow field, the formation process of flow distribution is presented. Then a quantitative analysis of the energy transfer and separation processes in vortex tubes driven by velocity gradient, temperature gradient, and pressure gradient is proposed. The viscous shear work, heat transfer, and turbulent heat transfer processes were analyzed separately. It was found that the main factors of vortex tube energy separation originated from the expansion of the inlet nozzle and the turbulent heat transfer process. At the same time, the viscous shear work and heat transfer processes also have a specific effect on the energy separation, in which the heat transfer process suppressed the energy separation effect of the vortex tube. In addition, its empirical results indicate that interactions among the turbulent heat transfer process, frictional dissipation, angular momentum conservation, and heat transfer should be considered in further studies.

Investigation of cold tube structure on flow characteristics and energy separation in vortex tube based on numerical and thermodynamic analyses

A combined approach of computational fluid dynamics modelling, experimental validation and thermodynamic analysis is used to investigate the effect of cold end tube geometry (namely, straight tube, divergent tube, convergent tube, and convergent-divergent tube) on flow characteristics and energy separation, which to improve the energy efficiency and sustainability of the vortex tube in industrial applications. The analyses indicate that the highest axial velocity (212 m/s) and swirl velocity (193 m/s) at different axial locations in the cold tube are demonstrated in the divergent and convergent-divergent structures, respectively. The divergent tube shows better energy separation at lower cold mass fraction, while the convergent-divergent tube is dominant at higher cold mass fraction. The highest coefficient of performance is found at μc = 0.6, with maximum cooling and heating energy transfer efficiencies of 0.112 and 0.103, respectively. By innovatively incorporating the work-heat transfer theory into structural investigation of cold tubes, it is found that tangential viscous shear effect is the dominant factor in energy separation process. It is noteworthy that the highest net energy transfer of 973 W is achieved by convergent-divergent tube at a cold mass fraction of 0.7.

Research on the prediction model of energy separation effect of vortex tube based on trajectory deflection characteristics and its numerical solution method

In this paper, in order to establish the energy separation mechanism of the vortex tube, the hydrodynamic behavior of the compressible fluid in the asymmetric cavity space is investigated, and a numerical model of the trajectory deflection behavior is deduced and established; in order to form the optimal design method of the structural parameters of the vortex tube, the force situation of the fluid microelements entering different regions of the vortex chamber of the vortex tube is analyzed, and the trajectory deflection equations are corrected by combining with the expansion behavior of the fluid and the characterizing equations of vortex strength, transportability, and vortex initiation characteristics are given. The characterization equations of vortex strength, transportability and vortex initiation characteristics are given, and the numerical simulation of their influence parameters is carried out; in order to realize the prediction of the vortex tube performance of a given structure, the multifactor Pearson thermodynamic map is used to correlate and analyze the experimental data of vortex tubes reported publicly in the past years, and the polynomial regression equations are designed and established for the prediction of the vortex tube's energy separation effect and the confidence level and the degree of coincidence of the prediction results are examined. The confidence level and degree of agreement of the prediction results were examined. It is found that: the trajectory deflection motion of the compressible fluid in the asymmetric cavity space is the result of the combined effect of structural air pressure bias and the expansion behavior of the incident fluid; in order to improve the vortex strength in the vortex tube, the vortex initiation chamber space should be as small as possible; the increase of the diameters of the hot-end pipe and the cold-end pipe is conducive to the enhancement of vortex strength, but at the same time, it weakens the vortex transport in the heat pipe; the vortex initiation chamber size has a negative correlation with the hot-end temperature rise, and the inlet fluid pressure has a The negative correlation between the size of the vortex chamber and the temperature rise at the hot end, the positive correlation between the increase of inlet fluid pressure and the resulting temperature rise, and the strong correlation between the inlet fluid pressure and the friction coefficient on the effect of energy separation; the predictive equations for the effect of energy separation obtained by the fitting are in good agreement with the real situation.

CFD simulation and thermodynamic analysis of energy separation in vortex tube using different inert gases at different inlet pressures and cold mass fractions

In this paper, extensive three-dimensional CFD simulations of vortex tube (VT) are conducted with five inert gases, namely helium, neon, argon, nitrogen, and carbon dioxide, to understand the influence of different properties of these gases on the flow phenomena and thermal performance of VT at wide range of cold mass fractions and inlet pressures. Molecular weights and specific heat ratios of the gases are found to significantly influence the values of velocity and temperature distributions inside VT, although the nature of the flow remains unaffected for different gases. Both hot and cold temperature separations increase for higher specific heat ratio of the gas, while heating and cooling powers are more for higher constant pressure specific heat and higher temperature separations. Coefficient of performance of VT vary significantly with cold mass fraction and inlet pressure, but remain majorly unaffected for different gases. Exergy analysis shows that at VT outlets, physical exergy is very much smaller than kinetic exergy. Outlet kinetic exergy is lost to the surroundings, without producing any desired cooling or heating effect. Therefore, physical exergy efficiency of VT, which is limited to 5% only, is of more practical value.

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.

Experimental and Numerical Study on Energy Separation in Vortex Tube with a Hollow Helical Fin

Experimental and Numerical Study on Energy Separation in Vortex Tube with a Hollow Helical Fin

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.

The thermal performance of a novel convergent valveless vortex tube

• A novel designed convergent valveless vortex tube. • Systematic comparison with conventional straight vortex tube. • Larger COPs were observed at certain cold mass fraction with some configurations. • Potential lower cost due to the simpler design and smaller dimension. Although the mechanism of the energy separation in a vortex tube still remains debatable, it is well agreed that the geometrical parameters have significant impacts on its thermal performance. The present parametric experimental investigation sheds new light upon the temperature variation and energy separation in a novel convergent valveless vortex tube, whereas the performance of a straight vortex tube is additionally measured for comparison. The temperature variation and energy separation of the convergent vortex tube were observed in all the tested configurations and the convergent valveless vortex tube was found to have a better working performance with some configurations comparing with the conventional straight vortex tube. It achieved a maximum increase of 25° in the temperature variation and 32% in the coefficient of performance (COP). This implies that it is possible to reduce the cost of a vortex tube and achieve a better performance in the meantime.

An Experimental Investigation towards Optimizing the Geometry and Material of Vortex Tube

The main interest of this study is to know the effect of tube material having different thermal conductivities, on the performance of the vortex tube energy separation. Also, the study evaluates the optimal tube length to diameter ratio (L/D) and the effect of inlet pressure on the performance of the vortex. Experimentation consists of three different tube materials, Acrylic, Aluminium and Copper. By maintaining the tube diameter 20 mm as constant, different L/D ratios of range 12.5 to 30 were considered by changing the length of the hot end of the tube. From the experimental data it is observed that the material with less thermal conductivity and optimal L/D ratio vortex tube has the maximum total temperature difference.

Thermodynamic performance of a CO2 vortex tube based on 3D CFD flow analysis

The vortex tube (VT) is a mechanical device that can simultaneously provide heating and cooling. In this work, a 3D CFD model is first developed to simulate the flow of CO2 within a vortex tube, and then it is validated with published experimental data. The assumed k-ε turbulence model uses Structured Hexahedral nodes generated in ANSYS Meshing. Only 1/6 of the geometry is required due to the symmetry of the VT. The validated CFD model is combined with a thermodynamic model of the VT to complete a parametric study, where the inlet pressure (550 kPa to 1300 kPa) and cold mass fraction (0.2–0.9) are the chosen parameters. The effects on the VT energy separation and performance are presented. Energy separation is discussed in terms of the hot exit and cold exit temperature differences, both with respect to the VT inlet temperature. Performance is characterized by cooling power, heating power, and both energy and exergy metrics. The numerical results show that the variation of the cold mass fraction from 0.2 to 0.9, for a fixed inlet pressure of 1300 kPa, causes the hot exit temperature difference to rise from 10 °C to 78.9 °C, while the cold exit temperature difference falls from 44.2 °C to 9.7 °C.

Experimental study of vortex tube energy separation under different tube design

Through experimental investigation, this study offers a closer look into the performance of the vortex tube energy separation under different geometrical parameters; mainly tube length, diameter and internal tapering angle. Also the study evaluates the effect of inlet pressure on the performance of the vortex. The data shows that the tested vortex tube has an optimum length between 66 mm and 158 mm, an optimum diameter between 9 mm and 26 mm and a tapering angle smaller than 4°. Finally the experimental data show that the higher the inlet pressure, the greater the temperature difference however there is a maximum value where performance starts to deteriorate due to inlet nozzle choking.

New Design of Ranque–Hilsch Vortex Tube: Helical Multi-Intake Vortex Generator

An experimental study is conducted to investigate the thermal energy separation in a counterflow vortex tube. The effects of the cold orifice diameter (), the number of tangential intakes (), and the helical length of intakes () on thermal separation and cold temperature of the vortex tube are investigated. Finally, the results are compared with the conventional tangential nozzle under the same experimental conditions. It is observed that the cold temperature difference of the new Ranque–Hilsch design was greater than the cold temperature difference of the classical Ranque–Hilsch vortex tube. Also, the vortex generator with , and has the highest effect on the vortex tube energy separation.

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.

Numerical simulation of heat transfer from a swirling flow to the lateral side of the vortex tube energy separation chamber

The results of investigation of heat transfer from an intensive swirling flow of gas to the lateral side of the vortex tube energy separation chamber are presented in the paper. The distribution of the heat transfer coefficient along the energy separation chamber is specified taking into account the effect of damping of the circumferential velocity component and the effect of heating of a potential peripheral whirl. Numerical calculations, the results of which are presented in this paper show the presence of a paraxial precessing vortex core and large-scale vortex structures - toroidal vortices periodically arranged on the periphery along the axis in the energy separation chamber. The dependence of the heat transfer coefficient on the value of the ratio of expansion of gas in the vortex tube, as well as changes in the temperature efficiency caused by increasing the energy separation chamber diameter is presented. It is shown that non-adiabacy has a greater effect on the thermodynamic efficiency of small-scale vortex tubes due to the increase of the relative fraction of the energy rejected from the lateral side in the form of heat.

Numerical Analysis of Hot Ends Length Effect on the Performance of Energy Separation in Vortex Tube

In this paper, effects of the vortex tube hot end lengths on the performance are studied, using a three-dimensional numerical fluid dynamic model. The hot end and cold end structure of vortex tube adapts the conical tube with the dilated side connecting a straight pipe. Structural mesh is employed. Different turbulence models are used, compared with experiment, considered of convergence and computing time, eventually, SST model is applied. In contrast to experimental data, numerical results are acceptable. By numerical analysis, it is observed that as the length of hot ends increases, the performance of energy separation increases significantly. However, while the length diameter ratio is more than 20, the performance does not increase any more. Even, it begins to decrease. Meanwhile, different hot end lengths flow is compared, and attemptable analysis is conducted to the flow phenomenon.

The second law analysis of natural gas behavior within a vortex tube

Vortex tube is a simple device without a moving part which is capable of separating hot and cold gas streams from a higher pressure inlet gas stream. The mechanism of energy separation has been investigated by several scientists and second law approach has emerged as an important tool for optimizing the vortex tube performance. Here, a thermodynamic model has been used to investigate vortex tube energy separation. Further, a method has been proposed for optimizing the vortex tube based on the rate of entropy generation obtained from experiments. Also, an experimental study has been carried out to investigate the effects of the hot tube length and cold orifice diameter on entropy generation within a vortex tube with natural gas as working fluid. A comparison has been made between air and natural gas as working fluids. The results show that the longest tube generates lowest entropy for NG. For air, it is middle tube which generates lowest entropy. Integration of entropy generation for all available cold mass fractions unveiled that an optimized value for hot tube length and cold orifice diameter is exist.

Exergy model of a vortex tube system with experimental results

A thermodynamic model has been used to investigate vortex tube energy separation. An equation has been derived for the rate of entropy generation. This equation is used to model the irreversibility term. A Gouy-Stodola type relation is used for the total irreversibility. The exergy-destruction rate and flow availability are estimated. A vortex-tube laboratory unit has been constructed to verify the theoretical analysis. A new approach has been used to optimize dimensions and operating conditions of a vortex-tube using exergy analysis.