Cold Mass Fraction Research Articles

Research on temperature performance prediction of vortex tubes based on artificial neural networks

Abstract This study constructs a hybrid neural network model by integrating the physical constraints of the Bernoulli equation and Nikolaev's formula. The model is designed to explore and predict the variation pattern of the cold end temperature in a vortex tube. The input parameters include inlet pressure, inlet temperature, and cold mass fraction, with the cold end temperature as the output parameter. The network employs a multilayer feedforward model and the Levenberg-Marquardt learning algorithm, using a hyperbolic tangent function as the activation function. To evaluate the statistical validity of the developed model, the coefficient of determination (R²) and root mean square error (RMSE) are utilized, along with an analysis of the model's uncertainty and robustness. The hybrid model achieves an R² of 0.9936 and an RMSE of 0.3392, demonstrating strong performance in terms of uncertainty and robustness. These results indicate that the model accurately predicts the cold end temperature variation in the vortex tube. Furthermore, the findings reveal an optimal pressure range (0.49 MPa to 0.76 MPa) and cold mass fraction range (0.1 to 0.2) that minimize the cold end temperature.

The impact of varying cold end diameter on the energy separation in Ranque-Hilsch vortex tube for different working gases: A CFD simulation and thermodynamic analysis

The vortex tube is a potential candidate for sustainable cooling due to its unique feature of energy separation without using any synthetic refrigerant. However, the investigation of energy separation and performance optimization always has been challenging due to its complex physics. In previous literature, the performance of vortex tube has been found affected by several parameters. In order to find the impact of varying cold end diameters with different gases, this paper investigates temperature separation in seven vortex tubes of different cold end diameters operating with three different working gases: He, N2, and CO2. A detailed thermodynamic analysis of their thermal separation performances at different cold mass fractions is presented for each working gas. Exergy analysis has also been conducted and discussed separately. As a result of this extensive investigation, it is found that the larger cold end diameter improves the performance of the vortex tube. The cold and hot temperature separation, cooling, and heating power at higher cold mass fractions are found to improve when operated with helium compared to other gas. However, the COP of cooling and COP of heating at higher cold mass fractions is found to be lower with helium. Improvements in the physical and kinetic exergies at the inlet and both outlets are observed with increasing cold end diameter, except for the kinetic exergy at the hot outlet. Helium gas is found to show more exergy at the inlet and both outlets among all three gases. The performance of vortex tube operating at higher cold mass fraction shows an improvement in exergies at outlets, except kinetic exergies at hot outlet. The total exergy efficiency decreases at cold outlet on increasing cold end diameter. However, the results of actual (physical) exergy efficiency shows an improvement at both outlet for larger cold end diameter. The actual exergy efficiency is calculated by considering the physical exergy alone because the kinetic exergy completely lost into the open atmosphere. Physical exergy efficiency at hot outlet is also found to increase on increasing cold mass fraction, while it decreases at cold outlet. Physical exergy efficiency of cooling and heating are found to more when operated with helium compared to nitrogen and carbon dioxide.

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.

An experimental investigation on the effects of the vortex tube material, swirl generator material and the tube length to diameter ratio on vortex tube performance

The current research investigates the effects of the swirl generator material, the tube length to diameter (L/D) ratio, and the vortex tube housing material on its performance. Two vortex tube were designed and constructed using either stainless or brass. In addition to testing different materials for the housing, 5 different materials were examined as potential options for the swirl generator, including stainless steel, brass, polyamide, acrylic and wood. All were having nozzle number of 6. The study encompassed three main areas: examining the impact of various L/D ratios on an entirely stainless vortex tube (ESVT) and an entirely brass vortex tube (EBVT), exploring various swirl generator materials at an optimal L/D ratio for the stainless vortex tube and the brass vortex tube, and investigating the influence of an optimal swirl generator material with varying L/D ratios for the stainless and brass vortex tubes. Operating conditions were controlled for all tests, the natural refrigerant, compressed air was used, the inlet pressure was set to 3.0 bar and the cold mass fraction was varied from 0.40 to 0.90. The results revealed that the performance of the ESVT was greater than the EBVT. The best combination was the polyamide swirl generator and brass vortex tube with an L/D ratio of 19.0. This resulted in the maximum isentropic efficiency of 0.27 at a cold mass fraction of about 0.47.

High-accuracy experimental study of performance characteristics of optimised Ranque-Hilsch vortex tube

In this paper we present high-accuracy experimental measurements of the performance characteristics of an optimised Ranque-Hilsch vortex tube of cylindrical counter-flow design. Although this is a relatively mature research area, the published high-accuracy experimental data with quantified measurement uncertainty is very limited. The purpose is to provide a reference data-set for CFD method validation and calibration. The vortex tube design is a performance-optimum based on existing literature. We characterize the temperature separation, energy separation, efficiency, and coefficients of performance for three inlet pressures (3.0 bar, 5.0 bar and 7.0 bar) and for atmospheric back pressure. Performance characteristics are presented as a function of cold gas mass fraction. The lowest non-dimensional cold-exit temperature (normalised by inlet temperature) was 0.87, the highest coefficient of performance (decrease in enthalpy flux of the cold stream normalized by work needed to compress air to the inlet pressure) was 0.137, and the highest isentropic efficiency (ratio of the actual energy lost by cold stream to energy that would have been lost in an isentropic expansion of the entire inlet stream from the inlet pressure to the cold-exit pressure) was 0.16.

Numerical simulations and local entropy generation in a two-phase transcritical carbon dioxide Ranque-Hilsch vortex tube

The Ranque-Hilsch vortex tube arouses a renewed interest as a robust expansion device able to produce thermal energy separation. However, its two-phase transcritical CO2 operation remains unclear. In this work, 3D computational fluid dynamics simulations are performed using the open-source SU2 solver which key features are the implicit time integration and the real gas density-based formulation. The homogeneous equilibrium two-phase model is coupled with both the k−ω shear stress transport and the standard k−ϵ turbulence closures while a fast tabulated version of the Span and Wagner equation of state enables to compute the CO2 properties. First, the validation is performed on pressure measurements, condensation onset positions and visualizations in a transcritical CO2 nozzle available in the literature. Then, the vortex tube transcritical CO2 temperature, energy and phase separations are thoroughly investigated as well as the integral and local entropy generations due to viscous and heat dissipations. The results reveal that the temperature separation is produced below the inlet temperature at both outlets due to real gas effects. It is also shown that the energy separation is reversed as well as the available vortex tube outlet powers for heating and cooling purposes. Furthermore, higher irreversibility due to fluctuating components is unveiled near the vortex tube sharp angles at high cold mass fraction and high inlet operating pressure. Throughout this analysis, compelling arguments in favor of the friction theory for the energy separation phenomenon are also disclosed. Overall, the present work gives useful operation guidelines and sheds light on the complex phenomena at play in a Ranque-Hilsch vortex tube for transcritical CO2 heat pumps.

Mapping a Lower Limit on the Mass Fraction of the Cold Neutral Medium Using Fourier-transformed H i 21 cm Emission Line Spectra: Application to the DRAO Deep Field from DHIGLS and the HI4PI Survey

We develop a new method for spatially mapping a lower limit on the mass fraction of the cold neutral medium by analyzing the amplitude structure of Tˆb(kv) , the Fourier transform of T b (v), the spectrum of the brightness temperature of the H i 21 cm line emission with respect to the radial velocity v. This advances a broader effort exploiting 21 cm emission line data alone (without absorption line data, τ) to extract integrated properties of the multiphase structure of the H i gas and to map each phase separately. Using toy models, we illustrate the origin of interference patterns seen in Tˆb(kv) . Building on this, a lower limit on the cold gas mass fraction is obtained from the amplitude of Tˆb at high k v . Tested on a numerical simulation of thermally bi-stable turbulence, the lower limit from this method has a strong linear correlation with the “true” cold gas mass fraction from the simulation for a relatively low cold gas mass fraction. At a higher mass fraction, our lower limit is lower than the “true” value, because of a combination of interference and opacity effects. Comparison with absorption surveys shows a similar behavior, with a departure from linear correlation at N H I ≳ 3–5 × 1020 cm−2. Application to the DRAO Deep Field from DHIGLS reveals a complex network of cold filaments in the Spider, an important structural property of the thermal condensation of the H i gas. Application to the HI4PI survey in the velocity range −90 < v < 90 km s−1 produces a full sky map of a lower limit on the mass fraction of the cold neutral medium at 16.′2 resolution. Our new method has the ability to extract a lower limit on the cold gas mass fraction for massive amounts of emission line data alone with low computing time and memory, pointing the way to new approaches suitable for the new generation of radio interferometers.

A numerical analysis investigation to optimize the performance of the Ranque–Hilsch Vortex tube by changing the internal tapering angle

A vortex tube is a device that separates compressed air into two streams: one with a higher temperature (hot stream) and the other with a lower temperature (cold stream). It is a popular cooling option because it is small, safe, and affordable. The main objective of this thesis is to examine the energy separation performance of RHVT by varying the internal tapering angles of convergent angles (2°, 1.75°, 1.5°, 1.25°, 1°, 0.75°, and 0.5°), straight angles (0°), and divergent angles (0.5°, 1°, 2°, 4°, and 6°), While the cold mass fraction is constant (0.317). Length-to-diameter ratio (Lt/Dt), inlet pressure, and the cold mass fraction were investigated to achieve the highest energy separation of RHVT. This thesis conducts a numerical study on the flow structure in a vortex tube using the shear stress transport k-ω turbulence model with viscous heating. The optimal energy separation occurred at a 1.75° convergent angle, Lt/Dt ratio of 3, the inlet pressure of 600 kPa, and a cold mass fraction of 0.56. The internal flow structure of the vortex tube consists of a forced vortex, transition, and free vortex regions, as shown by the static temperature radial distribution This distribution provides an understanding of the energy separation mechanism of the vortex tube by correlating it with the density gradient along the radial direction. The simulation results were validated by experimental data obtained from the literature for the same vortex tube parameters.

Mapping the Multiphase Structure of H i in the Low-latitude Intermediate-velocity Arch 1

We have analyzed the thermal and turbulent properties of the low-latitude intermediate-velocity Arch 1 (LLIV1). This was accomplished using archival H i emission and absorption data from two 21 cm line surveys: GHIGLS at 9.′4 resolution and DHIGLS at resolution. The spectral decomposition code ROHSA was used to model the column density of different thermal phases and also to analyze an absorption measurement against the radio source 4C +66.09. From the latter, we found spin temperature T s ∼ 75 K, cold gas mass fraction f ∼ 0.5, and turbulent sonic Mach number M t ∼ 3.4. Similar to the absorption line modeling against 4C +66.09, our best emission line decomposition model has no unstable gas across the whole field of view, suggesting that the thermal condensation and phase transition are not ongoing but rather have reached an equilibrium state. The cold phase of LLIV1 appears as a collection of elongated filaments that forms a closed structure within the field decomposed. These substructures follow the orientation of the overall large-scale cloud, along the diagonal of the GHIGLS field from northwest to southeast (in Galactic coordinates). The angular power spectrum of the cold phase is slightly shallower than that of the warm phase, quantifying that the cold phases have relatively more structure on small scales. Our spatially resolved map of the cold gas mass fraction in LLIV1 from DHIGLS reveals significant variations spanning the possible range of f, with a mean and standard deviation of 0.33 and 0.19, respectively.

Influence of flow straightener structure on energy separation performance of Ranque-Hilsch vortex tube based on energy and exergy analyses

The energy separation characteristics of vortex tube installed with flow straightener were experimentally investigated for better promotion of the application of vortex tube in the improvement of energy efficiency and sustainability. Systematic evaluation of the vortex tube with straightener was performed by applying a combined method of energy as well as exergy analysis, and the temperature separation process facilitated by the flow straightener was analyzed in depth. The effects of cold mass fraction (μc = 0.2–0.8), blades number (N = 0, 2, 4, 6 and 8), diameter ratio (ε = 0, 0.2, 0.4, 0.6 and 0.8), blade angle (θ = 0°, 30°, 60° and 90°) and installation position (Ls/L = 0.25, 0.45, 0.65 and 0.85) on cold and hot temperature differences, coefficient of performance, exergy efficiency and internal temperature field were investigated experimentally. The results show that as the blades number, blade angle and installation position increase, the cold and hot temperature difference and coefficient of performance first ascend and then descend. The presence of a hole in the center of flow straightener weakens the energy separation performance of vortex tube. A flow straightener with 4 blades, 0 diameter ratio, 60° blade angle and 0.65 installation position produces optimum energy separation performance and exergy efficiency.

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.

Feasibility and adaptability investigation on wet hydrogen dehumidification using vortex tube

This paper aims at exploring the feasibility of removing water vapour from wet hydrogen by vortex tube. For this purpose, a numerical model is developed for wet hydrogen condensing flow by adding two transport equations. Three different operating parameters, cold mass fraction, inlet pressure and molar fraction of water vapour, are discussed in terms of the impact on the flow and condensation process. The results show that the increase of the inlet pressure and the cold mass fraction can provide a favourable condensation environment for water vapour, which resulting in the increase of the number of droplets and mass fraction of the liquid. Condensation process is aggravated with high molar fraction of water vapour at inlet, although there is no significant change in pressure and temperature fields. Furthermore, a comprehensive study is performed by analysing the dehumidification performance and entropy generation. The maximum value of dehumidification performance up to 83.12% while cold mass fraction is 0.8218 and inlet pressure is 5 bar, which shows a good feasibility for wet hydrogen dehumidification.

A CFD investigation of flow separation in an elliptical and circular Ranque-Hilsch vortex tube

The present work investigates the flow physics inside an elliptical vortex tube. Two different 3D (three-dimensional) domains of circular and elliptical vortex tubes with four nozzles are studied. The cross-sectional area and length of the vortex tube are constant for both of its shape. The pressure at the inlet is 320 kPa for both the shapes and air as a working fluid. Standard k- ε turbulence model is used to predict the flow physics and temperature separation effect inside the tubes. The experimental and numerical findings of earlier researchers provide as validation for the present results. The deviation of the results is found within the permissible limit. The temperature separation phenomenon in an elliptical tube at various cold mass fractions is discussed. The range of cold mass fraction is 0.1 to 0.9. This work also examines the fluid characteristics and flow parameters by tracing the fluid particles within the tube. Fluid characteristics such as static pressure, density, total temperature, static temperature are evaluated. Also, the flow parameters like velocity magnitude, turbulent kinetic energy, axial velocity, and swirl velocity are discussed at the various radial locations inside the tube to get the flow pattern information. It’s an attempt to determine the feasible flow mechanism inside an elliptical vortex tube. The comparison between the circular vortex tube and the elliptical vortex tube has been done based on various fluid characteristics and temperature separation. It is found that energy separation is elevated in an elliptical tube by 49.89% at the hot end tube at 0.2 cold mass fraction whereas it is low for cold temperature separation as compared to the circular vortex.

Effect of right-angled ribbed geometry on the performance of a Ranque–Hilsch vortex tube: A numerical study

The working principle for the energy separation observed in a Ranque–Hilsch Vortex Tube (RHVT) is a matter that is widely debated and unsettled. It is, however, indisputable that modifications to the tube geometry can substantially affect the performance of the tube. In this paper, a three-dimensional computational fluid dynamic study is performed to investigate the enhanced performance of a geometrically modified vortex tube by studying the flow structure, heat transfer, and energy separation. The novel vortex tube is modeled in ANSYS FLUENT, similar to the original device: 3D Steady-state flow analysis using the standard k-ϵ turbulence model on a hybrid mesh. The results acquired are compared and found to demonstrate the increase in the observed energy separation in the novel geometry. The total increase in thermal separation for the novel design is observed to be 15.1 K at 0.9 Cold Mass Fraction, with an increase of 10 W in overall energy transfer. Compared to the nominal design, a maximum of 13.74 percent improvement in thermal separation. Furthermore, the flow structures are compared to understand the reason behind the increased performance. It is found that the factors responsible for the extent of separation of energy in the tube are: Higher Radial Pressure Gradient, Higher Circumferential, and Axial Shear Work, and Conductive Heat Transfer. Finally, an energy balance is carried out on the peripheral hot control volume to study the fundamental modes of energy transfer. The energy balance verifies that these factors are the prominent factors responsible for the observed increase in separation.

Analysis of the flow mixing and energy separation in a Ranque–Hilsch vortex tube based on an area ratio study

Ranque-Hilsch vortex tube is a pressure-driven thermal device that is an essential component of waste pressure utilization, especially in gas industry. However, the lack of an effective optimization design method and relative low efficiency restrict its development. In this study, the flow field and energy separation of five area ratios (AR) from 0.02–0.32 with the same inlet areas were analyzed based on the AR study of a vortex tube through experiments and numerical simulation. To determine the correlation of area ratio and energy separation, the basic flow field distributions are obtained and the flow structure is analyzed. The results show that for the fifth tube, denoted by AR5, the inlet mass flowrate remains largely constant (min = 9.27–9.24 g/s) with extremely small changes in the back pressure at hot exit (Ph = 11.2–18 kPa); in contrast, for AR1, the back pressure at hot exit (Ph = 10–148 kPa) and inlet mass flowrate (min = 6.8–4.26 g/s) vary significantly with increasing cold mass fraction. Moreover, despite using the same moderate cold orifice ratio of 0.48 for all the five tubes, back flow can occur at the cold exit even at an extremely large cold mass fraction of 0.82 for AR5. In addition, various flow structures and mixing and their corresponding causes inside the vortex tube are summarized. The comparison of the flow and thermal behaviors under the five ARs reveals opposite working patterns of reverse flow boundary and off-optimization under the non-flow mixing condition. These conflicting working patterns of reverse flow boundary can be attributed to the multi-parameter interaction of vortex tube. Thus, the criteria for tube optimization may unilaterally fail unless the precession frequency is studied. Finally, a performance evaluation index that quantifies the energy separation performance is proposed. The index serves to improve the tube optimization criteria and further develop the optimization of vortex tubes.

Exergy analysis and experimental investigation of various vortex tube material with different combination of vortex generators

An experimental investigation was conducted to study the effect of various materials on the performance of vortex tube. Beforehand, the recent progresses in the improvements on the performance of vortex tube (VT) and its efficiency, a literature survey has been discussed. The present work reports vortex tube performance augmentation considering four different materials vortex tubes and their orifice. The thermophysical properties of the material was considered to analyse the performance of vortex tubes for various materials. It was found that the aluminium vortex tube and its orifice achieved the highest performance among all the rest of the materials. The highest cold and hot temperature separation magnitude for Al VT and Al Vortex generator is 24 °C and 50 °C at an inlet pressure of 5 bar. The vortex tube of various materials had exact dimensions and specifications for an “apple to apple” comparison. Results show that the specific heat, thermal diffusivity, and thermal conductivity were the significant properties that affect the thermal performance of the VT. Furthermore, exergy analysis was done for the Al vortex tube and its orifice to predict the quality of available energy. It shows that high exergy destruction is found in hot regions for a high cold mass fraction.

Thermodynamic analysis of a transcritical CO[formula omitted] heat pump integrating a vortex tube

A thermodynamic model is used to analyze a transcritical carbon dioxide heat pump cycle integrating a vortex tube. The objective is to prove that a vortex tube is beneficial in raising heat pump efficiency. The novelty of the current work lies in implementing a sophisticated thermodynamic model of the vortex tube operating with carbon dioxide at high pressures or in a two-phase state. However, for all other components of the heat pump, a commercial library (TIL) associated with the Dymola software is used to simulate the system. A transcritical carbon dioxide conventional heat pump model is validated to determine the feasibility of implementing the TIL library. Then, the vortex tube heat pump is analyzed to test the heat pump performance and the effect of different parameters under various operating conditions. Of the parameters discussed, the hot exit pressure of the vortex tube and the desuperheater glycol mass flow rate are the most effective parameters on the desuperheater heating capacity and the overall coefficient of performance. Meanwhile, the hot exit pressure significantly controls the desuperheater glycol exit temperature, yet, with limitation. On the other hand, the variation of the cold mass fraction shows insignificant changes in the desuperheater glycol exit temperature. The final conclusion is that the heating coefficient of performance of the vortex tube heat pump is improved by a maximum of 43.7% when compared to that of the conventional heat pump.

Experimental and CFD Analysis on the Effect of Various Cold Orifice Diameters and Inlet Pressure of a Vortex Tube

An experimental investigation was conducted to investigate the effects of different cold orifice diameters and operating pressures of the vortex tube. A vortex tube test rig was employed to conduct the experiments for various cold orifice diameters and operating pressures. Cold orifice diameters range from 1 mm to 6 mm, whereas the pressure condition ranges from 2 to 5 bar. The vortex generators were made up of brass material having six inlet nozzles. It was found that the temperature separation of the vortex tube significantly depends on the cold orifice diameter of the vortex tube and operating pressure. The study demonstrates the deviation of cold temperature separation with respect to the cold orifice diameters and inlet pressure for different cold mass fractions. In addition, present experimental results are used to determine the optimum cold orifice diameter, which is 5 mm at 5 bar inlet pressure. The percentage improvement in average cold temperature separation for 5 mm cold orifice diameter is 66.18% compared to rest of the cold orifice diameters at an inlet pressure of 5 bar. The maximum cooling power separation is 0.08 kW at 0.3 cold mass fraction and inlet pressure of 5 bar. The CFD technique was approached to discuss the complex fluid flow inside the tube at various radial distances. A three-dimensional numerical study was done and validated with the present experimental work. It was found that the numerical results are in good agreement with the present experimental data.

CO(J = 1–0) Mapping Survey of 64 Galaxies in the Fornax Cluster with the ALMA Morita Array

We conduct a 12C16O(J = 1−0) (hereafter CO) mapping survey of 64 galaxies in the Fornax cluster using the Atacama Large Millimeter/submillimeter Array Morita array in cycle 5. CO emission is detected from 23 out of the 64 galaxies. Our sample includes dwarf, spiral, and elliptical galaxies with stellar masses of M star ∼ 106.3−11.6 M ⊙. The achieved beam size and sensitivity are 15″ × 8″ and ∼12 mJy beam−1 at the velocity resolution of ∼10 km s−1, respectively. We study the cold gas (molecular and atomic gas) properties of 38 subsamples with M star > 109 M ⊙ combined with literature H i data. We find that (1) the low star formation (SF) activity in the Fornax galaxies is caused by the decrease in the cold gas mass fraction with respect to stellar mass (hereafter, gas fraction) rather than the decrease of the SF efficiency from the cold gas; (2) the atomic gas fraction is more heavily reduced than the molecular gas fraction of such galaxies with low SF activity. A comparison between the cold gas properties of the Fornax galaxies and their environmental properties suggests that the atomic gas is stripped tidally and by the ram pressure, which leads to the molecular gas depletion with an aid of the strangulation and consequently SF quenching. Preprocesses in the group environment would also play a role in reducing cold gas reservoirs in some Fornax galaxies.

Numerical benchmark of a Ranque–Hilsch vortex tube working with subcritical carbon dioxide

A numerical benchmark of a Ranque–Hilsch vortex tube using subcritical carbon dioxide as the working fluid is performed. Predictions using different thermodynamic and two-equation turbulence models in high or low-Reynolds number formulations are compared to experimental data available in the literature. The results show that the k−ω SST model outperforms both the Standard k−ϵ model and the SAS-SST model in terms of cold and hot outlet total temperature predictions. Considering real-gas equations of state improves the accuracy even at subcritical conditions. In this regard, the multi-parameter Span–Wagner equation of state yields the best hot outlet total temperature prediction, especially at high operating pressure. Hence, the k−ω SST model in conjunction with the Span–Wagner equation of state are selected to examine internal flow features and discuss the validity of most common assumptions made by one-dimensional thermodynamic models. Finally, the exergy efficiency of the present vortex tube at various cold mass fractions is quantified.