Swirl Flow Generator Research Articles

Heat Transfer Enhancement of Laminar Nanofluids Flow in a Circular Tube Fitted with Parabolic-Cut Twisted Tape Inserts

Numerical investigation has been carried out on heat transfer and friction factor characteristics of copper-water nanofluid flow in a constant heat-fluxed tube with the existence of new configuration of vortex generator using Computational Fluid Dynamics (CFD) simulation. Two types of swirl flow generator: Classical twisted tape (CTT) and Parabolic-cut twisted tape (PCT) with a different twist ratio (y = 2.93, 3.91 and 4.89) and different cut depth (w = 0.5, 1.0 and 1.5 cm) with 2% and 4% volume concentration of CuO nanofluid were used for simulation. The effect of different parameters such as flow Reynolds number, twist ratio, cut depth and nanofluid were considered. The results show that the enhancement of heat transfer rate and the friction factor induced by the Classical (CTT) and Parabolic-cut (PCT) inserts increases with twist ratio and cut depth decreases. The results also revealed that the heat transfer enhancement increases with an increase in the volume fraction of the CuO nanoparticle. Furthermore, the twisted tape with twist ratio (y = 2.93) and cut depth w = 0.5 cm offered 10% enhancement of the average Nusselt number with significant increases in friction factor than those of Classical twisted tape.

Thermal characteristics in a heat exchanger tube fitted with triple twisted tape inserts

In the present study, the influences of triple twisted tapes on heat transfer rate, friction factor and thermal enhancement efficiency were experimentally investigated. The triple twisted tapes were used as swirl flow generators in the test section. The investigations were conducted using the mild steel triple twisted tapes with four different twist ratios (y=1.92, 2.88, 4.81 and 6.79) for Reynolds number ranging from 7200 to 50,200 under uniform heat flux condition. The experimental results demonstrated that the Nusselt number, friction factor and thermal enhancement efficiency increased with decreasing twist ratio. The results indicated that the presence of triple twisted tapes led to a higher increase in the heat transfer rate over the plain tube. The Nusselt number and friction factor of using the triple twisted tape inserts were found to be increased up to 3.85 and 4.2 times when compared with the plain tube, respectively. The heat transfer performance was evaluated based on the constant blower power and the performance was achieved to be 1.44 by the use of triple twisted tape inserts. Finally, correlations were developed based on the data gathered during this work for predicting the heat transfer, friction factor and thermal enhancement efficiency through a circular tube fitted with triple twisted tape inserts in terms of twist ratio (y), Reynolds number (Re) and Prandtl number (Pr).

Uphill Teeming Utilizing TurboSwirl to Control Flow Pattern in Mold

AbstractThe flow pattern has widely been recognized to have an impact on the exogenous non‐metallic inclusion generation in the gating system and mold flux entrapment in the mold in the uphill teeming process. The possible solutions of the flow pattern control are required to be reliable and practical in order to improve the yield and the ingot quality in the steel production. In this work, a mathematical model of a new novel swirling flow generation component, TurboSwirl, was studied to investigate the flow pattern of steel in the gating system and molds based on the authors' previous study. The same calculation method and boundary conditions were adopted. The results show that a much calmer initial filling condition with less fluctuations is achieved in the mold with a swirling flow by using the TurboSwirl compared to previous studies. In addition, the initial position of the mold powder bags can further be lowered in the mold due to a decreased hump height. Moreover, the difference between the hump height and the surface height in the present model has a maximum value of 83 mm, which gives a lower risk of mold flux entrapment. Furthermore, the maximum wall shear stress value can generally be lowered with less fluctuations after the first hump formation in the mold at 2.5 s from the teeming start. In conclusion, the initial filling conditions can be substantially improved by the use of TurboSwirl flow pattern control.

Effects of Electromagnetic Swirling Flow in Submerged Entry Nozzle on Square Billet Continuous Casting of Steel Process

In this study, a new method for swirling flow generation in submerged entry nozzle (SEN) in continuous casting of steel process has been proposed. A rotating electromagnetic field is set up around ...

Modeling of Initial Mold Filling with Utilization of Swirl Blades

The flow pattern has widely been recognized to have an impact on the exogenous non-metallic inclusion generation in the gating system and mold flux entrapment in the uphill teeming process. Thus, a well-controlled flow pattern during the teeming process can improve the quality of ingots and further increase the yield during steel production. The current study focused on investigating and optimizing the flow pattern of steel in the gating system and molds to improve steel cleanliness during the initial filling moment. A mathematical model considering a trumpet was initially compared to a reduced model only considering part of the runner channel. Thereafter, the influence of swirl blades implemented at the bottom of the vertical runner on the improvement of initial filling conditions in the molds was investigated in a model considering the entire mold system including a trumpet. The effects of a swirl blade orientation on a swirling flow were further discussed. The simulation results, when utilizing swirl blades, were also verified by plant trials performed at Scana Steel. In addition, a new novel swirling flow generation component, TurboSwirl, was studied in a model considering the entire mold system including a trumpet. The model was based on modifications of the refractory geometry at the elbow of the runners near the mold without the usage of an inserted flow control device in the gating system. Owing to its great potential for improving the flow pattern of steel during the initial filling moment, the effect of TurboSwirl on steel cleanliness was also studied. The results showed that the initial filling conditions during the uphill teeming process can be improved by using a swirl blade or a TurboSwirl in the gating system. This makes it possible to further decrease the initial position of mold powder bags. In addition, it reduces the possibilities of exogenous non-metallic inclusion generation in the gating system as well as mold flux entrapment in the mold during the uphill teeming process. However, the utilization of swirl blades created a considerable amount of droplets when steel entered the molds during the first couple of seconds, which also was verified by the plant trials. The introduction of TurboSwirl showed a greater potential than a swirl blade due to a more evenly distributed swirling flow. The DPM model adopted in the simulations revealed that the TurboSwirl can improve steel cleanliness by increasing the non-metallic inclusion collision rate both with respect to Stokes and turbulent collisions.

Heat transfer and thermal performance characteristics of heat exchanger tube fitted with perforated twisted-tapes

Twisted tape insert was applied as a swirling flow generator for the passive heat transfer enhancement in the present work. The influences of the perforated twisted tapes (PTs) on the heat transfer, pressure loss and thermal performance characteristics were investigated experimentally. The experiments were performed under uniform wall heat flux condition by using PTs with y/W = 3, 4 and 5, d/W = 0.11, 0.14 and 0.17 and s/W = 0.4, 0.6 and 0.8 where y is a twist length, d is a perforation hole diameter, s is a spacing between holes (pitch) and W is a tape width. The experimental results reveal that Nusselt number increased with decreasing s/W and y/W and increasing d/W. For the present range, the maximum heat transfer was obtained by utilizing the tape with s/W = 0.4, d/W = 0.17 and y/W = 3, which is higher than those obtained from the plain tube with and without typical twisted tape by around 27.4 and 86.7%, respectively. In addition, the empirical correlations for Nusselt number, friction factor and thermal performance are also proposed in the present paper.

Unsteady Simulations of the Flow in a Swirl Generator, Using OpenFOAM

This work presents numerical results, using OpenFOAM, of the flow in the swirl flow generator test rig developed at Politehnica University of Timisoara, Romania. The work shows results computed by solving the unsteady Reynolds Averaged Navier Stokes equations. The unsteady method couples the rotating and stationary parts using a sliding grid interface based on a GGI formulation. Turbulence is modeled using the standard k-e model, and block structured wall function ICEM-Hexa meshes are used. The numerical results are validated against experimental LDV results, and against design velocity profiles. The investigation shows that OpenFOAM gives results that are comparable to the experimental and design profiles. The unsteady pressure fluctuations at four different positions in the draft tube is recorded. A Fourier analysis of the numerical results is compared whit that of the experimental values. The amplitude and frequency predicted by the numerical simulation are comparable to those given by the experimental results, though slightly over estimated.

Heat Transfer Augmentation in a Circular tube and Squareduct Fitted with Swirl Flow Generators: A Review

The present paper is a review of research work in last decade on heat transfer enhancement in a circular tube and square duct. In the present paper emphasis is given to works dealing with twisted tape ,screw tape inserts because according to the recent studies, these are known to be economic tool in the field of heat transfer enhancement. Passive techniques, where inserts are used in the flow passage to increase the heat transfer rate, are advantageous compared with active techniques, because the insert manufacturing process is simple and cheap and these techniques can be easily employed in an existing heat exchanger. The thermohydraulic performance of above inserts depends on the various factors such as flow conditions, geometry of pipe and insert configurations. The present review is organized separately according to type of insets, pipe geometry, for laminar and turbulent flow respectively.

Comparative study of the uniformity of coating thickness of pellets coated with a conventional Wurster chamber and a swirl generator-equipped Wurster chamber

This study evaluated the performance of two bottom-spray coaters and the effect of pellet-size variability on coating uniformity. A conventional Wurster chamber was used for the first group of trials, and a Wurster chamber with a novel swirl-flow generator design was used for the second. The results confirmed that when using a conventional Wurster coating chamber, pellets with a smaller diameter receive significantly less coating material compared to those with larger diameters. The swirl generator-equipped Wurster chamber achieved close to uniform coating thickness regardless of pellet size. The ratio (MS) of the mass of dye deposited in the coating layer to pellet surface area indicates that coating was much more evenly distributed using the swirl-flow coater. Coating thickness was also analyzed using SEM micrographs and the results were in close agreement with the MS factor values. Inter-particle coating mass variation was also lower in case of swirl-flow coater. The results of this study show that a swirl-flow coater is suitable for coating particles of variable size. They also showed an improvement in coating process yield when using the swirl-flow coater.

Swirl flow analysis in a helical wire inserted tube using CFD code

An analysis on the two-phase flow in a helical wire inserted tube using commercial CFD code, CFX11.0, was performed in bubbly flow and annular flow regions. The analysis method was validated with the experimental results of Takeshima. Bubbly and annular flows in a 10 mm inner diameter tube with varying pitch lengths and inserted wire diameters were simulated using the same analysis methods after validation. The geometry range of p/ D was 1–4 and e/ D was 0.08–0.12. The results show that the inserted wire with a larger diameter increased swirl flow generation. An increasing swirl flow was seen as the pitch length increased. Regarding pressure loss, smaller pitch lengths and inserted wires with larger diameters resulted in larger pressure loss. The average liquid film thickness increased as the pitch length and the diameter of the inserted wire increased in the annular flow region. Both in the bubbly flow and annular flow regions, the effect of pitch length on swirl flow generation and pressure loss was more significant than that of the inserted wire diameters. Pitch length is a more dominant factor than inserted wire diameter for the design of the swirl flow generator in small diameter tubes.

A swirl generator case study for OpenFOAM

This work presents numerical results, using OpenFOAM, of the flow in the swirl flow generator test rig developed at Politehnica University of Timisoara, Romania. The work shows results computed by solving the unsteady Reynolds Averaged Navier Stokes equations. The unsteady method couples the rotating and stationary parts using a sliding grid interface based on a GGI formulation. Turbulence is modeled using the standard k-ϵ model, and block structured wall function ICEM-Hexa meshes are used. The numerical results are validated against experimental LDV results, and against designed velocity profiles. The investigation shows that OpenFOAM gives results that are comparable to the experimental and designed profiles. This case study was presented at the 5th OpenFOAM Workshop, held in Gothenburg, Sweden, as a tutorial on how to treat turbomachinery applications in OpenFOAM.

Influence of Short Helical Tape on Local Convective Heat Transfer and Thermal Performance Characteristics in Turbulent Decaying Swirl Flow

This paper reports the experimental investigation of local convective heat transfer enhancement, flow friction and thermal performance factor behaviors in the tube fitted with the short helical tapes (SHTs) acting as decaying swirl flow generators. The tapes with three different helical tape angles (? = 90°, 135° and 180°) and three different channel numbers (N = 2, 3 and 4 channels) were tested under the uniform wall heat flux condition. The performance of each tape is compared with the performance of the plain tube subject to the same pumping power. The experimental results show that the heat transfer rates and friction factors of the tube with SHTs are respectively in range of 1.15 to 1.9 and 1.49 to 2.31 times of those in the plain, corresponding to thermal performances between 0.98 and 1.46. The correlations for Nusselt number (Nu) as a function of Reynolds number (Re), Prandtl number (Pr), helical tape angle (?) and the number of channel (N) are also developed.

A new vortex generator geometry for a counter-flow Ranque–Hilsch vortex tube

Abstract In this study, a new geometry is introduced for the cold end side (i.e. where the swirl flow is introduced into the tube), which is called ‘helical swirl flow generator’ . Effect of the helical length of the swirl flow generator on the performance of the vortex tube are investigated for varying values of other geometrical parameters as a function of the cold mass fraction, y c . Finally, it’s disclosed that the effect of the helical length on the performance changes critically according to the value of L/D .

Prevention Method of Swirling Flow Generation in Discharging Liquid in the Reactor Vessel

Prevention Method of Swirling Flow Generation in Discharging Liquid in the Reactor Vessel

Prevention Method of Swirling Flow Generation in Discharging Liquid in the Reactor Vessel through a Nozzle

Prevention Method of Swirling Flow Generation in Discharging Liquid in the Reactor Vessel through a Nozzle

An experimental study on the effect of the valve angle of counter-flow Ranque–Hilsch vortex tubes on thermal energy separation

An experimental study is conducted to investigate effects of the conical valve angle on thermal energy separation in a counter-flow vortex tube. A new geometry is designed for the cold end side, which is called ‘ helical swirl flow generator’. Combined and interactive effects of the helical length of the swirl flow generator, the ratio of the tube length to the tube inner diameter ( L/ D), the inlet pressure and especially the angle of the conical valve on the performance of the vortex tube are comparatively investigated as a function of the cold mass fraction, y c . Four different conical valves have been used with the angle of 30°, 45°, 60° and 75°. Finally, it is observed that the effect of the valve angle on the performance changes according to the value of L/ D and, it has a weak influence on the system performance.

Study of the Uniformity of the Coating Thickness of Pellets Coated by Wurster and Swirl Flow Generator Equipped Coater

The problem emerging from particle coating is how to manufacture particles with just enough material deposited to achive the desired result [1]. [...]

Novel method for cooling plasma welding torch head

The performance of a design using swirling flow with a U shaped return passage to cool the tip of a plasma arc torch is numerically investigated. The new cooling scheme is first compared with the cooling design of a Nippon Steel plasma torch. Using a hypothetical swirling flow of different vortex angles but the same coolant flowrate and external heating boundary conditions as for the Nippon Steel torch, the flow and temperature fields for both torches were analysed using a computational fluid dynamics package and the results were compared. The results show that the present cooling scheme not only provides a more axisymmetric temperature field, but also results in lower averaged surface temperatures. Using a swirling flow generator implemented upstream of the tip of the U shaped region, numerical results indicate that improved cooling performance can be achieved with only a slight increase in coolant pumping head when compared with the cooling design for the Nippon Steel torch.

Development of Swirling Flow Generator in Immersion Nozzle.

It is very critical to develop a cheap, simple and safe swirling generator because an introduction of swirl motion is very effective to control the flow in the continuous casting mold and refining process. Here, a twist-tape-swirling-blade is proposed and its characteristics are investigated. Obtained results are as follows; (1) Numerical results obtained by the k-e turbulence model and experimental results coincide with each other for the tangential velocity distributions at the outlet of the swirl blade. (2) A slightly strained tangential velocity can be seen just below the swirling blade, but the tangential velocity becomes axi-symmetric at a downstream position, which is within the distance of 100 mm from the outlet of the swirling blade. (3) Knowing the axial velocity and twist ratio of the swirl blade, the corresponding tangential velocity and pressure drop can be deduced through the relationship between dimensionless radial position and tangential velocity.

Thermal-Hydraulic Performance of a 2 MWt Sodium-Heated, Forced Recirculation Steam Generator Model

The results of LMFBR (Liquid Metal Fast Breeder Reactor) steam generator model tests conducted in a 2 MWt sodium-heated test facility at prototypical Breeder Reactor Demonstration Plant conditions are presented. This includes heat transfer performance data and a sodium-side heat transfer correlation for a seven-tube bayonet tube forced recirculation evaporator with identical tube geometry to a proposed LMFBR Demonstration Plant evaporator. The departure from nucleate boiling characteristic of the bayonet tubes employing swirl flow generators and the steam-side heat transfer coefficients in the transition boiling regime were measured. The steam-side boiling stability characteristics of the evaporator were evaluated and a summary of the results are presented. The results also include heat transfer performance data for a helical coil superheater containing two active tubes and one inactive tube. Sodium temperature distribution data for the evaporator measured at various load conditions indicating steep axial temperature gradients in the sodium inlet plenum region are presented along with sodium temperature distribution data for the superheater. Finally, sodium-side instability data associated with series operation of the models, both containing cover gas spaces, are presented along with sodium temperature fluctuation data measured in the inlet plenum of the evaporator.