Delta-wing Vortex Generators Research Articles

Machine Learning Analysis of Thermal Performance Indicator of Heat Exchangers with Delta Wing Vortex Generators

In this work, the design features of delta wing vortex generators (DWVGs) on the thermo-hydraulic performance of heat exchangers are investigated using machine learning. Reynolds numbers, attack angle, length, wing-to-width ratio, and relative pitch ratio of DWVGs were used as descriptor variables, with Nusselt numbers, friction factors, and performance evaluation criterion (PEC) serving as target variables. Decision tree classification revealed the pathways leading to high or low values of the performance variables. Among many of those pathways, it was found that high Reynolds numbers (between 8160 and 9800) and high attack angles (greater than or equal to 47.5°) lead to high Nusselt numbers. On the other hand, an attack angle between 41° and 60°, a Reynolds number less than 8510, and a wing-to-width ratio greater than or equal to 0.4 causes a high friction factor. Finally, the PEC is likely to enhance when the Reynolds number is higher than or equal to 10,300 and the attack angle is between 47.5° and 60°. In addition to the decision tree analysis, SHapley Additive exPlanations (SHAP) analysis (a part of explainable machine learning) was also applied to reveal the importance of design features and their positive and negative effects on the target variables. For example, for a Nusselt number as the target variable, the Reynolds number was found to be the most influential variable, followed by the attack angle and the relative pitch ratio, all of which had a positive impact on the target. It was then concluded that machine learning methods could help provide strong insights into the configuration design features of heat exchangers in DWVGs to improve their efficiency and save energy.

Efficiency Enhancement in Air Heat Exchangers: Analyzing the Impact of Size Ratio and Geometric Modifications on Delta-Wing Vortex Generators

Efficiency Enhancement in Air Heat Exchangers: Analyzing the Impact of Size Ratio and Geometric Modifications on Delta-Wing Vortex Generators

Investigation of a delta wing Vortex Generator

The flow and the effect on a DU08-W-210 airfoil using a conventional and a delta wing vortex generator (VG) has been investigated numerically using ANSYS Fluent and STAR CCM+ CFD solvers. The numerical results from the two CFD programs are very consistent. Both VG geometries delay boundary separation at the trailing edge of the airfoil and thus increase the lift and lift to drag ratio. The overall aerodynamic loads on the airfoil are quite similar for the two different VG geometries, but the created vortices give a slightly different distribution of the skin friction in the wake behind the VGs. The vortex created by the delta wing VG for the same conditions and size as the conventional triangular VG is slightly stronger and probably caused by the fact that the surface creating the vortices is placed higher up in the boundary layer and thus experience a higher inflow velocity. A method to measure the strength and core radius of the created vortices using a Lamb-Ossen vortex is described.

Comparison of Turbulent Flow and Heat Transfer in a Rectangular Channel with Delta Wing and Winglet Type Longitudinal Vortex Generators

Comparison of Turbulent Flow and Heat Transfer in a Rectangular Channel with Delta Wing and Winglet Type Longitudinal Vortex Generators

Experimental and Numerical investigation of implementing a novel vortex generator: A Perforated Delta Wing Vortex Generator (PDWVG) on the performance of Solar Air Collector

Experiments were carried out for the numerical investigation of heat transfer enhancement in a solar air collector using different types of baffles and vortex generators. In this study, the vortex generator was implemented to increase the efficiency of the solar air collector. The variations in Nusselt number, pressure drop, friction coefficient, thermal and exergy efficiency in four collectors with different baffles arrangement (type A, B, C, D) were investigated. Type A was chosen as the optimum collector for implementing the vortex generator on the absorber surface. In the solar air collector the effects of using a novel vortex generator - the Perforated Delta Wing Vortex Generator (PDWVG), in comparison with a flat one - the Flat Delta Wing Vortex Generator (FDWVG), were considered. In order to determine the maximum efficiency of the solar air collector, four different pitch ratios of vortex generators were studied. The Nusselt number and pressure drop increased with Reynolds number but the friction coefficient decreased with Reynolds; the experimental and numerical results revealed that the thermal and exergy efficiency decreased from a specific range. The comparison of PDWVG and FDWVG showed that presence of holes on the novel vortex generator, led to reduced pressure drop and increased the heat transfer between the air flow and the absorber surface. Increasing the number of vortex generator rows had a slight effect on increasing the studied parameters. The results showed that collector type A with ep=0.55 of PDWVG improves the energy and exergy efficiency 4.43% and 5.29% respectively.

Numerical investigation of convective heat transfer enhancement by a combination of vortex generator and in-tube inserts

The application of both the vortex generators and twisted belts were investigated in literature as they are effective in improving heat exchanger thermal performance. In this paper, a novel method to enhance the heat exchanger thermal performances obtained by combining the vortex generator and twisted belt is proposed. The circular tube thermo-hydraulic characteristics were numerically studied by combining the twisted belt and delta wing vortex generators (DWVGs). The effects of twist ratio, attack angles, pitch and vortex generator arrangement were investigated. The emphasis was put on obtaining the optimal parameters. The Reynolds number was based on the hydraulic diameter channel flow, which ranged from 5000 to 25,000. The results indicate that the most favorable vortex generator arrangement is staggered arrangement when the twisted belt twists counter-clockwise. The optimal twist ratio is 4, and PEC increases with the increase in the angle of attack and decrease of the vortex generator pitch. When considering the conditions studied in this paper, the PEC can be improved by 96% ~ 128% compared with the smooth tube. Said improvements are mostly obtained when using the novel combination structures with the staggered arrangement, optimal twist ratio of 4, attack angle of 75°, and pitch of 1.5D.

A second law analysis for turbulent convective flow through panel type radiator equipped with vortex generators

An irreversibility analysis is arranged for the turbulent convective flow through the panel type radiator equipped with the vortex generators. Delta wing vortex generators are installed inside the system to disrupt the flow and enhance the heat transfer rate. However, vortex generator may affect the second law efficiency of the system, which should be investigated. The increase in the entropy production restricts the thermodynamic advantages of the vortex generators. The influences of several parameters, including the attack angle of vortex generator β, space between the back edge of vortex generator and hot surface of the panel, d, and Re number, Re, on the velocity and temperature characteristics, entropy production owing to viscous friction and heat transfer, and Be number are studied. The results attained by the present numerical investigation are validated with the data reported in the literature to ensure about the accuracy of the numerical solver. The outcomes revealed that the entropy production owing to viscous friction is increased with increasing the attack angel of vortex generators and space between the back edge of vortex generator and the hot surface of the panel. The larger values of entropy production owing to heat transfer are produced when the vortex generators are placed farther from the hot surface of the panel. Both entropy production owing to viscous friction and heat transfer increase with placing the vortex generators inside the panel. The substrate of high Be number grows along the panel length and occupies most of the panel at the exit section. By the way, the entropy production owing to viscous friction is dominate term at the entrance of the panel owing to the high velocity gradient of the developing flow regions.

Influence of Delta Wing on Wall Erosion Characteristics of Mitred Pipe Bends Handling Coal Slurries

The present work investigates the influence of delta wing vortex generators placed inside circular mitred pipe bends, handling high density and erosive coal slurries. Coal slurry flowing at different Reynolds numbers ranging from 2000 < Re < 10,000 is tested. Mitred bends having a flow turning angle (α) of 45°, formed by joining segments of pipe, with varying number of joints (1, 2 and 3) were assessed numerically. Delta wing was positioned inside the pipe at different angles (β = 30°, 60°, 90°, 120° and 150°). Coal slurry viscosity and density varied to understand the influence of solids loading (φ = 30%, 35%, 41%, 42%, 43%, 44%) on the wall erosion characteristics. Computational studies are carried out on a 90° turning circular sectioned smooth pipe bend to study the impact of various turbulence models, and the results are validated with appropriate results from the literature. A turbulence model having good correlation with the literature results is identified and adopted in the present study. Highest turbulent mixing at the pipe outlet and reduced peak wall shear stress were considered as criterion for selecting best delta wing orientation, though with a higher pressure drop penalty. Unique delta wing induced vortex flow evolutions in the streamwise direction is reported.

Heat transfer enhancement in panel type radiators using delta-wing vortex generators

In this paper, a three-dimensional numerical simulation is used to analyze the performance of delta-wing vortex generators for enhancing the heat exchange in panel type radiators, which are widely used in electric power transformers. The study is focused on natural convection and buoyancy-driven flows, which are common working conditions for this type of heat exchanger. First, the performance of a single delta wing between parallel vertical plates is analyzed to establish the best combination of characteristic parameters to obtain the highest thermal enhancement factor. It is found that separating the vortex generator from the surface of the panel has positive effects in this sense. Then, with the selected configuration, a set of delta-wing arrays is placed on the surface of the heat exchanger, and the resulting thermo-fluid dynamic is analyzed. The total heat flux and local/global heat exchange coefficients are reported. Using these passive devices, the overall heat transfer improves by 12%.

Double-sided delta-wing tape inserts to enhance convective heat transfer and fluid flow characteristics of a double-pipe heat exchanger

One of the challenges in the development of heat exchangers is to minimize their energy consumption. This can be achieved by enhancing the heat transfer rate, which will boost the thermal performance of heat exchangers. Delta-wing vortex generators fitted in a double-pipe heat exchanger will generate vortices with more intermixing of the flowing fluid, and provide the improvement of convective heat transfer of the internal flow. In this study, double-sided delta-wing (T-W) tape inserts were designed to enhance convective heat transfer of a double-pipe heat exchanger. The effects of the wing-width ratio (0.31, 0.47, and 0.63) on the heat transfer and fluid flow characteristics of the heat exchanger were investigated by experiments where water was used as the working fluid and the Reynolds number was varied from 5300 to 14,500. The results were compared with those obtained for a plain tube and tube with longitudinal strip (L-S) insert. The T-W tape insert (wing-width ratio: 0.63) results in the highest average Nusselt number, where the average Nusselt number is higher by 177% relative to that for the plain tube. Despite the significant heat transfer enhancement, the friction factor is 11.6 times higher relative to that for the plain tube, indicating that friction loss is more pronounced due to the presence of T-Ws. The T-W tape insert (wing-width ratio: 0.63) also results in the highest thermal performance factor (1.15). The Nusselt number, thermal performance factor, and friction factor of the heat exchanger increases as the wing-width ratio of the T-Ws increases. Based on the experimental data, empirical correlations were developed to predict the Nusselt number and friction factor of the double-pipe heat exchanger with T-W tape inserts.

A Comparative Study of the Enhancement of Heat Transfer by Delta Wing Vortex Generators and V Shaped Dimples Using Experimentation and CFD

Heat transfer augmentation without considerable pressure drop is one of the most important issues nowadays and, hence, different active and passive methods are used for the same. In this study, two methods are used, one by use of delta wing vortex generators and the other is V-shaped dimples to enhance heat transfer. Delta wings are mounted on a flat plate using inline and staggered arrangement. The analysis is performed for delta wing vortex generators of 0.6mm thickness on an Aluminium plate of 150mm × 150mm size and 10mm thickness with an angle of attack of delta wings of 450, a variation in velocities of 2.5m/s, 3.5m/s and 4.5m/s with inline and staggered positions of vortex generators. The experiments were performed on 150mm × 150mm × 10mm aluminum plate with V- shaped dimples with pitch 3.2D, where D = diameter of dimple. V-dimples with δ/D = 0.2, 0.3, 0.5 are investigated, where δ= dimple depth. Two different arrangements of V –dimples, namely inline and staggered, were used during experimentation and the results obtained were compared to the flat surface without dimples. The experimentation was carried over a rectangular duct with aspect ratio 3:2. The Values of h, Nu, f and the overall thermal performance of the dimpled surface are compared with those from flat surface under the same conditions. The results of both cases are compared to each other and to the bare plate also. Using the CFD analysis in both cases, it has been observed that the heat transfer enhancement using Delta wing vortex generators is effective (almost 10-15% more) compared to V-shaped dimples.

Comparison of Heat Transfer Enhancement in a Diffuser by inserting Wing Vortex Generators and Protrusions

The influence of delta wing vortex generators and protrusions on the heat transfer performance in a diffuser has been experimentally investigated. Two diffuser angles are studied. One and two vortex generator (wing) pairs and protrusions are considered. The velocity profile at the diffuser inlet is uniform, and the flow is a developing one. The wing vortex generator and protrusions are placed on the heated surface. It is observed that the heat transfer enhancement is more with the two pair wings case. The Re based on inlet velocity and diffuser length is in the range 2.3–3.6E05. The wing case exhibits a higher enhancement than that of protrusion. The heat transfer enhancement using one and two pair wings and protrusions is also studied. The results are presented in the form of Nusselt number ratio (rough to smooth) for both at constant Re and at constant dissipation (pumping power). The maximum enhancement is 98% at constant Re and 70% at constant dissipation. The enhancement increases with the angle of attack of the wing vortex generator and decreases with the diffuser angle and with Re.

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Heat transfer enhancement for laminar flow in tubes using curved delta wing vortex generator inserts

The results of an experimental study for heat transfer enhancement in a circular tube fitted with a curved delta wing vortex generator insert are presented here. Local heat transfer coefficient and overall pressure drop measurements in the laminar flow regime with water as the working fluid are presented. Curved delta wing vortex generators were attached on the opposite sides of a central rod at specific axial locations to form the insert. The thermo hydraulic performance of these inserts with different geometrical parameters viz. pitch to projected length ratio (p/pl), angle of attack (α), and circumferential contact length to tube inner diameter ratio (b/d) was studied. The local heat transfer measurements for both smooth and rough surface sides of the tube are reported with the tube Reynolds number (Re) varying between 250 and 1500. The average Nusselt number ratio with and without the insert (Nua/Nus), at equal Reynolds number (Re) is found to be in the range of 5.0–15.0. The performance ratio R3, (Nua/Nuc), based on equal pumping power and constant heat transfer area, is found to be in the range of 1.0–6.0.

ENHANCEMENT OF RATE OF HEAT TRANSFER USING VORTEX GENERATORS IN AIR HEATER

There are many applications in engineering industry that require heat addition or removal and a wide variety of heat exchange devices are used for different applications. Performance of improving coefficient of heat trsnsfer and pressure drop reducing becomes essential in all applications. Most of thermal devices like high temperature gas turbines , heat exchangers, electronic equipment, convective heat transfer plays an major role in most of the engineering applications. There are many methods to enhance rate of heat transfer. Delta wing vortex generators or promoters of turbulence are often used to calculate the flow field and they can give a worth full effect on the performance of thermal device. Many researchers have been studied extensively the applications of heat transfer which involves internal flow and mixed convection in ducts and non-circular ducts such as, rectangular, square, triangular. To attain higher coefficient of heat transfer, it is necessary that the surface of heat transfer flow is to be made turbulent. However, energy for producing such turbulence has to come from the blower or fan and the maximum turbulence leads to excessive power requirement to make the air flow through the duct. Therefore maximum turbulence must be produced in the region which is very near to surface of heat transfer i.e. in the laminar sub-layer only Excessive friction losses can be avoided by making flow should be not unduly disturbed and it is done by making the height of the roughness element to be small as compared with the dimensions of duct. The roughness element height (e) and pitch (P) are the most important parameters to characterize the roughness shape and arrangement. All these parameters namely , angle of attack (β), relative roughness pitch (P/e), relative roughness height (e/D) are usually specified as dimensionless parameters.

Flow characteristics of air in square duct using delta wing vortex generators

Summary Performance improvement in terms of improving heat transfer coefficient and reducing pressure drop becomes essential in heat exchange applications and a large number of methods for reducing pressure drop exist in the literature and the present work is an investigation on use of delta wings as vortex generators for reducing pressure drop. Methodology includes air from a blower entering the test section through orificemeter and differential-micro manometer to measure the flow rate and pressure drop across the test section. Depending upon the pressure drops, friction factors for smooth and rough surface of the duct are estimated. The effect of geometrical parameters of delta wing and duct aspect ratio on friction factor ratios are reported Based on Reynolds number in the range of 8000−24000. The geometrical parameters of vortex generators varied in this study were the pitch-to-vortex generator height ratio (p/e), vortex generator height to duct hydraulic diameter ratio (e/Dh), aspect ratio of vortex generator (ar). Results are reported for 0.1

Thermal performance in solar air heater channel with combined wavy-groove and perforated-delta wing vortex generators

An experimental investigation on thermal performance improvement in a solar air heater channel with combined wavy-groove and delta-wing vortex generator (WVG) placed on the absorber plate having a uniform wall heat-flux is carried out. The Reynolds number based on the hydraulic diameter of the channel ranges from 4800 to 23,000. The effect of the combined groove and WVG on the heat transfer and pressure drop in the channel in terms of respective Nusselt number and friction factor is examined. Investigated parameters of the WVG mounted on the grooved absorber are three wing porosity area ratios (called porosity ratio, Ah/Aw = 0.031, 0.085 and 0.167) and four groove-wing distance to channel-height ratios (g/H = 0.4, 0.5, 0.75 and 1) at a single attack angle (α = 45°). The experimental result reveals that at g/H = 0.5, the smaller Ah/Aw provides the highest Nusselt number and friction factor around 6 and 30 times over the smooth channel, respectively, but the optimum thermal performance is at Ah/Aw = 0.085 and g/H = 0.5. The combined devices give the thermal performance augmentation at about 37.7–46.3% higher than the groove alone and also at about 1.5–12.5% above the combined groove and non-perforated WVG (without hole).

The Effect of Streamtube Contraction on the Characteristics of a Streamwise Vortex

The ingestion of a vortex by an aero-engine is potentially an area of concern for current and future aircraft-engine configurations. However, there are very little experimental data on the characteristics of a streamwise vortex undergoing ingestion through a contracting streamtube. To address this dearth of knowledge, the ingestion of a streamwise vortex has been studied experimentally using stereoscopic particle image velocimetry (stereo PIV). A subscale model of an aircraft intake has been used to generate a contracting capture streamtube, and an isolated streamwise vortex has been generated upstream of the intake using semispan NACA 0012 and delta wing vortex generators (VGs). A range of contraction ratios, vortex Reynolds numbers, and vortex initial conditions have been examined. Measurements on planes perpendicular to the freestream flow show that the vortex undergoes notable levels of intensification through the contraction streamtube. The characteristics of the vortex are dependent on the streamtube contraction level, the initial aerodynamic characteristics of the vortex, and the trajectory that the vortex follows inside the capture streamtube. Results from inviscid, incompressible vortex filament theory have been compared with the experimental data. At relatively low streamtube contraction ratios this theory provides a good estimate of the vortex characteristics. However, at higher contraction levels, there are notable levels of diffusion, which render the vortex less intense than that anticipated from vortex filament theory.

Heat transfer and friction factor characteristics of turbulent flow through a circular tube fitted with vortex generator inserts

Abstract Local heat transfer coefficients and average pressure drop measurements for turbulent flow in a circular tube fitted with a nonconventional insert are presented here. The insert was fabricated with a central rod on which curved delta wing vortex generators were attached on opposite sides at specific axial locations. The influence of pitch to projected length ratio (p/pl), height to tube inner diameter ratio (e/d) and angle of attack (α) on the heat transfer performance are reported here. Air was used as the working fluid and local heat transfer measurements for both smooth and rough surface sides of the tube are reported for fully developed turbulent flow with Reynolds number (Re) varying between 10,000 and 45,000. The average Nusselt number ratio with and without the insert (Nua/Nus), at constant Reynolds number (Re) is found to be in the range of 1.3–5.0. The Nusselt number ratio (Nua/Nuc), based on equal pumping power is found to be in the range of 1.0–1.8. Empirical correlations are developed for Nusselt Number and friction factor in terms of Reynolds number (Re), pitch to projected length ratio (p/pl), height to tube inner diameter ratio (e/d) and angle of attack (α).

Study on Enhanced Heat Transfer and Structural Optimum for Combination Vortex Generator in Spiral Channel

The array configuration of delta wing and elliptical cylinder vortex generator in the spiral surface channel was studied. By changing the assembly distance s, the triangle wing vortex generator angle of attack α, the elliptical cylinder vortex generator angle of attack β to research the heat transfer and resistance properties under different working conditions. The research model as follow: the heat-medium is water-vapor [H2, the cold medium of flow is air, Steam temperature is 400K and air inlet temperature is 293K, the Reynolds number ranging from 4000 to 7000.The optimum structure was determined by using numerical simulation method and orthogonal experiment method. The result shows the optimization structure of the combination vortex generator: α=45°, β=45°, s=90mm. Compared with the normal structure, the heat transfer enhancement comprehensive effect of the optimization structure raised about 36.2%~47.6%.