Vortex Tube Research Articles

Numerical analysis on performance of two-phase vortex-tube

R41 gas and R1234yf droplets are used in the study as working fluids. Three-dimensional computational fluid dynamics is utilized to investigate the behavior of fluids in single-phase and two-phase vortex tubes, as well as the influence of cold flow fraction on the performance of them. The results show that small addition of droplets does not change the special working mechanism of the vortex tube. Two-phase vortex tubes are effective devices that can separate high pressure flow into cold flow and hot flow. But temperature difference at both cold and hot ends in the case of two-phase vortex tube is less than that of single-phase vortex tube at the same cold flow fraction. The maximum cold temperature differences of the single-phase and two-phase vortex tubes are 11.97 K and 10.54 K respectively when μ = 0.3. A maximum hot temperature difference of 29.54 K is achieved in the single-phase vortex tube when μ = 0.9. In contrast, a two-phase vortex tube exhibits a maximum hot temperature difference of 17.11 K at μ = 0.8. Additionally, the peak refrigerating capacity of the single-phase and two-phase vortex tube are 40.47 W and 38.51 W at μ = 0.7.

Numerical simulation of radial duel-stage nozzle vortex cooling at the leading edge of a gas turbine blade

Thermal failure is one of the major challenges faced by the leading edge of gas turbines, which significantly affects the improvement of their efficiency. The vortex cooling technique has become a promising solution to address this issue. Radial duel-stage nozzle vortex cooling (RDNVC) model, featured with a vortex tube and two sets of nozzles, is proposed based on the radial single-stage nozzle vortex cooling (RSNVC) configuration. This novel structure aims to intensify turbulence within the cooling fluid at the nozzle inlets, thereby improving heat transfer at the leading edge. The model improves turbulence in the cooling fluid, promoting better heat transfer at the leading edge. Numerical simulations with the SST k-ω turbulence model were performed to analyze heat transfer and flow characteristics at varying Reynolds numbers (Re). The results show that the non-uniform inlet velocity in RDNVC increases turbulence and vorticity inside the vortex tube, leading to improved heat transfer. At the same cooling airflow rate, RDNVC increased the global average Nusselt number by 23.56% compared to RSNVC. Nu increases with Re. Among the three models, RDNVC(6–2) (nozzle heights of 6 mm and 2 mm) showed the best thermal performance, followed by RDNVC(2–6), while RSNVC had the lowest thermal performance. For the same pressure drop, RDNVC(2–6) achieved an 8.42% improvement in heat transfer efficiency over RSNVC. Based on Re and geometry parameters, the empirical correlation for the global average Nusselt number of RDNVC is also proposed.

Computational Investigation of the Operating Mechanism of the Ranque–Hilsch Vortex Tube

Abstract The Ranque–Hilsch vortex tube is a device that splits an incoming flow into two outgoing streams, but with the peculiar property that one stream exits at a lower total temperature than the incoming flow and the other at a higher total temperature. This temperature separation is accomplished without any moving parts, electronics or external power supplied to the device. Despite the passage of nearly a century since discovery of the effect, there remains a dearth of understanding regarding the mechanism responsible for the phenomenon. In fact, the literature contains competing theories with little evidence providing support. A promising technique to discern the responsible mechanisms for the energy transfer from the ultimately cold stream to the ultimately hot stream is to define a stream tube in a computational simulation of the flow that propagates upstream from the exits such that the stream tube interface separates the hot flow from the cold flow. In this article, we apply this method to a three-dimensional, full-volume analysis of the flow within a vortex tube using a computational simulation that was thoroughly validated against experiments on a physical replica of the computational geometry. In this novel study, the integral form of the energy equation was used to quantify all forms of the energy transfer within the vortex tube. The results demonstrate that the phenomenon of temperature separation is attributable primarily to viscous work in the radial direction due to the circumferential flow, with a lesser contribution from heat transfer in the radial direction.

Zero carbon emission and cold energy recovery: Thermodynamic evaluation of a combined ammonia gas turbine and transcritical CO2 cycle

This research proposes a combined cycle system that integrates an ammonia gas turbine with a self-condensing transcritical CO2 (tCO2) power cycle. For the first time, the cold energy of liquid ammonia is utilized to condense the gaseous CO2 at the vortex tube outlet in the tCO2 cycle. This approach resolves the issue of incomplete CO2 condensation in the vortex tube and reduces the number and variety of compression components, ensuring efficient use of the cold energy of liquid ammonia. Additionally, by splitting the CO2 after the pump, the pinch point issue in the low-temperature recuperator (LTR) is addressed. This paper establishes a simulation model of the combined cycle, analyzes the feasibility of the cycle from a thermodynamic perspective, and investigates the impact of the split ratio, vortex tube inlet temperature and pressure, vortex tube outlet pressure, turbine inlet temperature and pressure and sCO2 turbine inlet temperature and pressure on the performance of cycle. This research offers a new method for the efficient use of both high-temperature waste heat from the ammonia gas turbine and the cold energy of liquid ammonia, as well as a novel solution to the CO2 condensation challenges in the tCO2 cycle.

Simulation-Based Design for Inlet Nozzle of Vortex Tube to Enhance Energy Separation Effect

The vortex tube, also known as the Ranque–Hilsch vortex tube, is a mechanical device that separates compressed gas into hot and cold streams. It offers a reliable and cost-effective solution to a wide range of cooling applications, as it operates without moving parts, electricity, or refrigerants. Research on vortex tubes has primarily focused on understanding the mechanisms of energy separation and optimizing cooling performance by altering geometric operational parameters. In this study, a Computation Fluid Dynamics (CFD) analysis was conducted to enhance the prediction of energy separation performance and improve the overall energy efficiency of the vortex tube. First, the geometry of the experimental device was modeled to closely match its actual shape, unlike the simplified geometries commonly used in previous CFD studies. Simulations were then carried out with variation in grid systems and turbulence models, and the results demonstrated improved agreement with experimental data compared to those reported in previous studies. Finally, simulations with a modified shape of the inlet nozzle shape were performed, revealing that the energy separation effect of the vortex tube could be enhanced by approximately 15% with an increased inlet expansion ratio (ϵ) while maintaining a constant nozzle length.

Effect of cyclone on the CO2 separation characteristics of a vortex tube

Carbon capture and storage has been suggested as a strategy for combating climate change. Cryogenic carbon capture has been demonstrated to effectively capture CO2 from the exhaust gas of fossil fuel combustion at the plant level, but it comes at the cost of high energy consumption. Vortex tubes are devices that mechanically separate compressed incoming gas into hot and cold streams that can potentially facilitate cryogenic carbon capture. In this study, a vortex tube was applied to separating CO2 from an air/CO2 mixture. The design of the vortex tube was modified by the addition of a specially designed vortex generator and a cyclone cone to the cold outlet. The effects of gravity, the inlet nozzle size, and shape of the cyclone cone were evaluated. The results showed that a vertical setup incorporating the effect of gravity improved the CO2 separation performance. Increasing the inlet nozzle velocity increased the CO2 concentration at the cold outlet. The cyclone cone was more effective at angles of 10° and 20° than at angles of 30° or greater. Finally, the effectiveness of the cyclone cone was more pronounced with higher CO2 concentrations at the inlet.

Poynting Flux of MHD Modes in Magnetic Solar Vortex Tubes

Magnetic flux tubes in the presence of background rotational flows, known as solar vortex tubes, are abundant throughout the solar atmosphere and may act as conduits for MHD waves to transport magnetic energy to the upper solar atmosphere. We aim to investigate the Poynting flux associated with these waves within solar vortex tubes. We model a solar vortex tube as a straight magnetic flux tube with a background azimuthal velocity component. The MHD wave solutions in the equilibrium configuration of a vortex tube are obtained using the Shooting Eigensolver for SolAr Magnetohydrostatic Equilibria code and we derive an expression for the vertical component of the Poynting flux, S z , associated with MHD modes. In addition, we present 2D visualizations of the spatial structure of S z for different MHD modes under different background flow strengths. We show that S z increases in the presence of a background rotational flow when compared to a flux tube with no rotational flow. When the strength of the background flow is greater than 100 times the strength of the perturbation, the S z associated with non-axisymmetric (∣m∣ > 0) modes increases by over 1000% when compared to a magnetic flux tube in the absence of a background rotational flow. Furthermore, we present a fundamental property of solar vortices, namely that they cannot solely produce an upward Poynting flux in an untwisted tube, meaning that any observed S z in straight flux tubes must arise from perturbations, such as MHD waves.

Optimization Study of the Structural Parameters of an Artificial Percolation Intake Riverbed Based on a Numerical Orthogonal Test

Research on water abstraction techniques in sandy rivers is crucial for addressing water scarcity issues in northern China. This study introduces an artificial percolation water intake riverbed structural model designed to prevent sand intake and facilitate the extraction of clear water from sandy rivers, the main function of which is to artificially construct a helical flow field to realize the separation of water and sand and, at the same time, percolate the water. In this paper, we use a numerical orthogonal test method to study the influence of structural parameters and their combinations on water extraction by percolation, and the preferred combination of structural parameters. The main conclusions of this paper are as follows: Under the condition of certain structural parameters of the artificial riverbed, the single-width flow rate has an important effect on the mean circumferential flow rate of the vortex tube and the vortex tube seepage volume. The effect of different structural parameters on the mean circumferential flow rate of the vortex tube and the vortex tube seepage varies in magnitude. The longitudinal slope of artificial riverbed i had the greatest and most significant effect on the mean circumferential flow rate of the vortex tube, and each structural parameter had some effect on the vortex tube seepage Q but not to a significant level. When the sand content of the water flow is 15 kg/m3 and the maximum sand grain size of the suspended mass is 2 mm, the optimal structural parameter combinations of the artificial riverbed under different working conditions are as follows: Combination 20 is the optimal structural parameter combination for q = 0.3 m2/s; Combination 24 is the optimal structural parameter combination for q = 0.6 m2/s; and Combination 24 is the optimal structural parameter combination for q = 0.9 m2/s. The present study is of great significance for understanding the influence of each structural parameter and its combination on the effect of the water intake and sand discharge of an artificial percolation intake riverbed, and for optimizing the combination of the structural parameters of an artificial percolation intake riverbed.

Solar Vortex Tubes. III. Vorticity and Energy Transport

This study investigated the mechanisms of vorticity generation and the role of vortex tubes in plasma heating and energy transport. Vortex tubes were identified using the instantaneous vorticity deviation technique in the MURaM data set of a simulated solar plage region of the solar photosphere. Within 3D kinetic vortex tubes, the misalignment of the magnetic pressure and the inverse of the density gradient, rather than baroclinic effects, primarily drive vorticity within the tubes. During their lifetime, vortices become less dense as the Lorentz force pushes plasma outwards against pressure gradients. In the simulated upper photosphere, the Lorentz force contributes to adiabatic cooling and heating by expanding or compressing the plasma around the vortex tubes. In turn, vortex motion affects the magnetic field, enhancing current generation and intensifying the Lorentz force, which may further increase adiabatic cooling and heating. Moreover, our results confirm that vortices can significantly boost viscous and ohmic heating on intergranular scales in the photosphere. They generate more magnetic than kinetic energy, with energy transport by Poynting flux notably nonuniform and dominant at the vortex boundaries. This creates energy circulation in which the net upwards Poynting flux can enhance chromospheric plasma heating and support chromospheric temperatures.

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.

Utility of Certain AI Models in Climate-Induced Disasters

To address the current challenge of climate change at the local and global levels, this article discusses a few important water resources engineering topics, such as estimating the energy dissipation of flowing waters over hilly areas through the provision of regulated stepped channels, predicting the removal of silt deposition in the irrigation canal, and predicting groundwater level. Artificial intelligence (AI) in water resource engineering is now one of the most active study topics. As a result, multiple AI tools such as Random Forest (RF), Random Tree (RT), M5P (M5 model trees), M5Rules, Feed-Forward Neural Networks (FFNNs), Gradient Boosting Machine (GBM), Adaptive Boosting (AdaBoost), and Support Vector Machines kernel-based model (SVM-Pearson VII Universal Kernel, Radial Basis Function) are tested in the present study using various combinations of datasets. However, in various circumstances, including predicting energy dissipation of stepped channels and silt deposition in rivers, AI techniques outperformed the traditional approach in the literature. Out of all the models, the GBM model performed better than other AI tools in both the field of energy dissipation of stepped channels with a coefficient of determination (R2) of 0.998, root mean square error (RMSE) of 0.00182, and mean absolute error (MAE) of 0.0016 and sediment trapping efficiency of vortex tube ejector with an R2 of 0.997, RMSE of 0.769, and MAE of 0.531 during testing. On the other hand, the AI technique could not adequately understand the diversity in groundwater level datasets using field data from various stations. According to the current study, the AI tool works well in some fields of water resource engineering, but it has difficulty in other domains in capturing the diversity of datasets.

Sustainable Diamond Burnishing of Chromium–Nickel Austenitic Stainless Steels: Effects on Surface Integrity and Fatigue Limit

This study aims to evaluate the influence of lubrication and cooling conditions in the diamond burnishing (DB) process on the surface integrity and fatigue limit of chromium–nickel austenitic stainless steels (CNASSs) and, on this basis, identify a cost-effective and sustainable DB process. Evidence was presented that DB of CNASS performed without lubricating cooling liquid satisfies the requirements for a sustainable process: the three key sustainability dimensions (environmental, economic, and social) are satisfied, and the cost/quality ratio is favorable. DB was implemented with the same values of the main governing factors; however, four different lubrication and cooling conditions were applied: (1) flood lubrication (process F); (2) dry without cooling (process D); (3) dry with air cooling at a temperature of −19 °C (process A); and (4) dry with nitrogen cooling at a temperature of −31 °C (process N). Conditions A and N were realized via a device based on the principle of vortex tubes. All four DB processes provide mirror-finished surfaces with Ra roughness parameter values from 0.041 to 0.049 μm, zones with residual compressive stresses deeper than 0.5 mm, and increases in the specimens’ fatigue limit (as determined by the accelerated Locati’s method) compared to turning and polishing. Processes F and D produce the highest microhardness on the surface and at depth. The process D introduces maximum compressive residual axial and hoop stresses in the surface layer. The dry DB processes (D, A, and N) form a submicrocrystalline structure with high atomic density, which is most strongly developed under process D. When high fatigue strength is required, DB with air cooling should be chosen, as it provides a more favorable cost/quality ratio, whereas dry DB without cooling is the most suitable choice for applications that require increased wear resistance.

Numerical investigation of the collision of a vortex pair upon a solid wavy wall

The vortex dynamics produced by the collision of a vortex pair with a solid wavy wall are examined numerically using a proposed high-order vortex particle method. The influences of the Reynolds number (ReΓ) of the vortex pair, the wavelength (λw), and the wave amplitude (Aw) of the wall on the induced vortex structures, interactions among vortices, and the instability and reconnection of secondary vortices are discussed. The boundary layers at the top of ripples separate first to form the secondary vortices moving around the primary tubes. Meanwhile, the boundary layers at the bottom of ripples detach late, move vertically upward, and then form incomplete vortex loops due to an unsuccessful reconnection of the secondary vortices. The ReΓ effects cause the appearance of various vortex structures, such as incomplete primary vortex loops from the bottom of ripples at ReΓ=1000, secondary vortex loops due to interactions of the first loops with the wall at ReΓ=2000, and hairpin vortices at ReΓ=4000. The wavelength of the wall induces instability in the secondary vortex tubes. This instability on the secondary tubes appears at the top of ripples at λw=2r0, while it spreads over the whole secondary vortices at λw=4r0, where r0 is the initial spacing between the primary vortex tubes. This instability results in various wavy tubes that robustly interact with the primary tubes. Due to the effects of Aw, the primary vortex tubes significantly decay with time compared to those in the flat wall case.

Numerical Simulation Study of an Artificial Percolation Riverbed and Its Hydraulic Characteristics under Different Reynolds Numbers

The direct extraction of clear water from a sandy river is a difficult task and can only be achieved through specific engineering measures. This paper proposes an artificial percolation riverbed structure for extracting clean water from sandy rivers, using a numerical simulation to study the flow field distribution characteristics of the structure under clean water conditions. The main conclusions are as follows: When the percolation vortex tube opening rate is 1.4%, the vortex tube with or without opening the percolation hole has little influence on the distribution characteristics of the flow field in the artificial riverbed, and the purpose of water extraction can be achieved while constructing a helical flow field. The axial flow velocity and circumferential flow velocity of the vortex tube cross-section under different Reynolds numbers show the distribution of a low-flow velocity close to the center of the vortex tube, and a high-flow velocity close to the vortex tube side-wall area. The average axial flow velocity and average circumferential flow velocity of the vortex tube show a trend of increasing and then decreasing distribution along the axial axis of the vortex tube in the direction of the sediment transport flume. The mean axial flow velocity of the vortex tube along the axis of the vortex tube toward the sediment transport flume and the mean circumferential flow velocity both show a distribution trend of increasing and then decreasing. At the junction of the vortex tube and the sediment transport flume, there are obvious pressure changes, and the pressure changes drastically under the same horizontal line. Along the direction of the bottom line of the vortex tube, the pressure at the vortex tube is obviously greater than that at the sediment transport flume. The vortex of the artificial percolation riverbed is mainly concentrated in the vicinity of the vortex tube, and the maximum value of the vortex intensity generally occurs at the junction of the vortex tube and the sediment transport flume. With the increase in the Reynolds number, the vortex intensity has an overall increasing trend, and the distribution of the vortex is more complex. This study helps to elucidate the distribution characteristics of the flow field in the artificial percolation riverbed, and it provides a reference basis for the future study of the flow field of artificial percolation riverbeds of sandy rivers.

Algorithm for controlling the operation of energy-efficient gas production points

During the operation of gas distribution networks, the gas pressure when moving to the consumer decreases at the gas distribution point (GDP). When the gas pressure at the hydraulic fracturing site decreases, a decrease in the temperature of the transported gas is observed (Joule-Thompson effect or adiabatic expansion). As a result of a decrease in gas temperature, condensate may form in the form of liquid fractions and crystalline hydrates. As a result, it becomes possible that the operation of the hydraulic fracturing pressure regulator will deviate from the planned mode with possible condensate adhesion on the walls, impulse tubes and cavities of the regulator, affecting the operation of instrumentation, contamination of filters, etc. Traditionally, this is dealt with by maintaining the required gas temperature through partial combustion of the transported gas with heating of the hydraulic fracturing room and gas. But always, when burning gas, certain volumes of it were consumed, and therefore funds, and at the same time gas combustion products entered the atmosphere. In addition, gas combustion, that is, the use of open fire, increased the risks of hydraulic fracturing. In this paper, it is proposed another algorithm for the gas preparation process when supplying it to the consumer: to abandon additional gas costs and the disadvantages indicated with the combustion procedure, while maintaining the necessary quality of gas preparation for its further use using a simple conversion of bypass lines with two vortex channels. The basis for this method of gas preparation was a series of works by the Department of Physics on the theoretical substantiation of statistical patterns in the formation of directed molecular flows. The proposed physical statistics is based on the universal mechanism of long-range wave action (ULWM), the selective nature of which at the stage of continuous streamers determines both the speed of the wave component and the loss of rotational degrees of freedom of molecular motion. Thanks to this, we observe thermal effects inherent in the Ranque-Hilsch effect. On this physical basis, an explanation is given for the operation of both vortex tubes and a number of atmospheric phenomena, including tornadoes and the appearance of lightning. It is on the basis of ULWM that a description of the physical essence of the operation of two vortex channels (condensation and decondensation) is given with a gain in energy and quality of preparation of the gas mixture.

Computational study of energy separation in convergent-divergent vortex tube for different throat diameters, throat locations, inlet pressures, and working gas

This paper aims to improve the energy separation performance of vortex tube with a converging–diverging design of the hot tube. Three-dimensional computational fluid dynamic simulations are conducted to explore energy separation in a straight vortex tube (SVT) and in convergent-divergent vortex tubes (CDVT) with variations in throat diameter, throat position, inlet pressure, and working gas. Detail analysis of flow and temperature distributions reveal that flow is accelerated in the converging part of CDVT, which increases the transfer of shear work from the axial region to the peripheral region of CDVT compared to SVT, thereby producing significantly higher cold temperature separation in CDVT compared to SVT. CDVT with non-dimensional throat diameter of 0.40 is observed to produce the maximum value of cold temperature separation, which is up to 9 K (∼35 %) higher than the same obtained with SVT. Coefficient of performance of cooling obtained with this CDVT is found to be up to ∼ 30 % higher compared to SVT. When CDVT is operated with helium, ΔTc is found to have mean increment of 20 K (56 %) compared to SVT being operated with air. Overall, CDVT having non-dimensional throat diameter of 0.40, throat position in the middle of the hot tube, and operating with helium is recommended for obtaining maximum temperature separation performance in a wide range of cold mass fraction.

Productivity, energy, and exergy analyses of a water desalination system-based vortex tubes with different configurations: An experimental implementation

The present implementation explores the use of vortex tubes (VTs) as an alternative thermal technology for water desalination systems (WDSs). VTs are utilized to provide hot air for evaporating salt water in the evaporator, while simultaneously supplying cold air to condense the water vapor in the condenser. The study investigates the influence of a number of operating parameters, including inlet water temperature (Ti,w), cold mass ratio (CR), and vacuum pressure (pvac) on the performance of WDS-based VTs through experimental analysis. Different configurations of VTs are tested for WDS applications, including WDS-based single vortex tube (VT), WDS-based two series vortex tubes (2SVTs), and WDS-based two parallel vortex tubes (2PVTs). Performance metrics such as the evaporation heat (QEvap), desalinated water production (DWP), gain output ratio (GOR), and exergy performance are evaluated for each configuration. Results show that the WDS-based 2SVTs exhibits the highest QEvap; while the WDS-based 2PVTs demonstrates the lowest value. Correlations are proposed to predict DWP for different configurations of WDS based on pvac, Ti,w, and CR with a maximum deviation of ±12.2 %. Furthermore, the WDS-based 2SVTs achieves the best GOR of 2.5 at an inlet water temperature of 80 °C, representing a significant improvement compared to the WDS-based VT and 2PVTs. The exergy efficiency (ηex) increases with higher CR, and the WDS-based 2SVTs ensures the best exergy performance, and its maximum overall ηex equals 78.2 %.

CFD aided finite element modeling for spot cooled vibration assisted turning of Ti6Al4V alloy

Machining of titanium alloys using hybrid cutting techniques is acquiring importance now-a-days due to the benefits of integrating two or more processes. This study explores such a novel in-house developed hybrid cutting technique, which is a combination of ultrasonic assistance and vortex tube based spot cooling with CO2 gas as coolant for machining Ti6Al4V alloy. CFD aided finite element model was developed and experimentally validated for this novel technique termed spot cooled vibration assisted turning (SCVAT). Parametric study of cooling (nozzle inclination, nozzle tool distance, nozzle diameter, coolant pressure and cold fraction), vibration (amplitude) and machining parameters was carried out in order to identify the role of each parameter on cutting force and cutting temperature. The parametric study showed that flow variables (cold fraction and coolant pressure) are more significant than nozzle variables in influencing cutting force and cutting temperature. SCVAT reduced cutting temperature by 21.66% and 3.45%, respectively, than VAT and spot cooling alone. However, cutting force reduced by 7.65% compared to spot cooling and increased by 11.78% compared to VAT. Overall observations from the CFD aided Finite element model revealed superior performance of SCVAT than its individual counterparts.

LDA-Based Experimental Investigation of Velocity Pulsations in the Vortex Tube

LDA-Based Experimental Investigation of Velocity Pulsations in the Vortex Tube

Flow dynamics and heat transfer characteristics of flows past a zigzag cylinder in a bounded domain

A comprehensive numerical and experimental study is conducted to investigate the flow dynamics and heat transfer characteristics of flows past a novel wavy-axis circular cylinder placed symmetrically between two parallel walls. For comparison, the flow past a corresponding straight-axis cylinder within the same bounded domain is also studied. The investigations were primarily conducted at Reynolds numbers of 626 and 680, based on the average velocity and diameter of the cylinder, with a blockage ratio of 0.42, based on the widest area of the channel. At these flow conditions, the straight cylinder expectedly showed a “reverse” von Kármán type wake. However, the special zigzag cylinder showed fundamentally distinct flow patterns at the wake leading to a significant drag reduction and a heat transfer enhancement, compared to the performance of the straight cylinder. The pressure drop of the zigzag cylinder is 14 % and 19.4 % lower than that of the straight cylinder, with a higher convective heat transfer coefficient of 24 % and 9 %, respectively, for Reynolds numbers of 626 and 680. The substantial drag reduction is attributed to the formation of steady flow pattern in the wake indicating the suppression of unsteady vortex shedding. The heat transfer enhancement was mainly caused by the formation of elongated vortical structures principally aligned in the streamwise direction. The creation of these streamwise vortex tubes tends to more efficiently mix the fluid between the near-wall area and the core region of the channel than the near-planar vortex shedding associated to the straight cylinder. It was shown that the 3D shape of the zigzag cylinder generates a spanwise velocity component, which results in the creation of a dominant streamwise vorticity component that eventually develops into sustained vortex tubes.