Winglet Vortex Generators Research Articles

Heat Transfer Enhancement Simulation Employing Flat and Curved Winglet Vortex Generator Pairs with Punched Holes

Heat Transfer Enhancement Simulation Employing Flat and Curved Winglet Vortex Generator Pairs with Punched Holes

Entropy generation and thermal behavior of microchannel fitted with punched curved vortex generators

Utilizing curved vortex generators (VGs) has emerged as a promising way to improve heat transfer in heat exchangers. However, research on the placement of punched rectangular curved winglet VGs on two opposing heat transfer surfaces of microchannel heat exchangers is limited. Through experiments and simulations, the effects of five perforation positions and three pitches on fluid flow and heat transfer were examined. This analysis is performed in the turbulent flow regime (2500 < Re < 3500) and the governing equations are solved by using SST k-ω model, assuming that the fluid is incompressible, has constant thermal properties, and ignores the effects of thermal radiation and gravity. Metrics such as the Nusselt number ratio, friction coefficient ratio, secondary flow intensity, thermal enhancement factor, and entropy generation are used to analyze the flow dynamics of mixed vortices. The results indicate that different perforation positions significantly affect the vortex characteristics, altering heat transfer and pressure loss. Furthermore, the pitch of the VGs plays a crucial role in governing heat transfer and frictional losses. Specifically, the heat transfer rate increased by 12.1 % to 61.1 % compared to empty tubes, accompanied by a rise in pressure loss ranging from 50.6 % to 115.1 %. To validate the findings, the principle of entropy generation was utilized. Notably, under conditions of a Re of 2500, a perforation position proximal to the VG's leading edge (θ = +12°), and a pitch of 15 mm, a remarkable thermal enhancement factor of 1.29 was achieved.

Thermal performance augmentation of microchannel using curved rectangular winglet vortex generators having rectangular perforation

This article innovatively introduces the application of punched curved rectangular wing vortex generators positioned on opposing sides of a rectangular microchannel. Through a comprehensive approach combining numerical simulations and experimental investigations, the flow dynamics and heat transfer performance of these VGs under turbulent conditions are thoroughly examined. This analysis is performed in the turbulent flow regime, specifically at Reynolds number ranging from 2500 to 3500. The governing equations are solved by using SST k-ω model. To evaluate the behavior of mixed vortices, a range of key metrics is utilized, including the Nusselt number ratio, friction coefficient ratio, and thermal enhancement factor (TEF). The study encompasses variations in opening angles (θ = 0°, 5°, 10°, 15°) and pitch ratios (PR = P/H = 15, 30, 45) to determine their impact on the overall system performance. The findings reveal that the punched curved rectangular winglet VGs effectively induce mixed vortices, leading to an enhancement in local heat transfer rates. However, the presence of fluid jets hinders the formation of other vortices. Compared to a smooth tube, the maximum TEF also experiences a 26 % rise. To validate the findings, the field synergy principle and entropy generation theory was utilized.

Enhancing heat transfer with a hybrid vortex generator combining delta wing and winglet designs: A numerical study using the GEKO turbulence model

This paper presents a numerical study on the enhancement of heat transfer in a solar air heater (SAH) duct with Hybrid Vortex Generators (HVG) placed periodically along the flow direction on its heated wall (absorber plate) for fluid flow and convection heat transfer at Reynolds numbers between 4121 and 25,365. HVGs consist of a trapezoidal winglet (TWL) for HVG-winglet-base-angles θ = 45° and 30°, or a combination of a delta winglet (DWL) with a delta wing (DWG) for angles θ = 26°, 18° and 12°. The angle of attack for the winglet (TWL or DWL) in the HVG is set at 30°, while the merging angle with the DWG is 45°, and the relative height BR = e/H = 0.48 remains constant. Initially, the effects on heat transfer and friction factor of Trapezoidal Winglet Vortex Generator (TWVG) and HVG45 (θ = 45°) obtained by basic modification on TWVG are investigated under the same flow conditions for PR = 1.5 and Re = 11,205. Subsequently, parametric studies are performed for five different HVG-winglet-base-angles (θ = 45°, 30°, 26°, 18° and 12°) and three different longitudinal pitch ratios (PR = PL/H = 1.0, 1.5 and 2.0). The calculations are performed with ANSYS Fluent 2021R2 based on the finite volume method. In order to model turbulent flow, the GEKO (GEneralized K-Omega) turbulence model recently developed by ANSYS and based on the k-ω formulation is used. HVG45, obtained by basic modification on TWVG, produces slightly stronger and more effective longitudinal vortices compared to TWVG, showing a 3.87 % decrease in friction factor and a 4.11 % increase in Nusselt number and thus a 5.43 % increase in Thermal Enhancement Factor (TEF). Parametric investigations are conducted across a range of values for both θ and PR. The highest rise in friction factor is attained at the lowest Reynolds number, reaching a value of f/f0 = 54.52, while the most significant enhancement in heat transfer rate is noted at the highest Reynolds number, with Nu/Nu0 = 5.86 for θ = 45° and PR = 1.0. The TEF reaches 2.42 at the lowest Reynolds number for the HVG18 with a winglet-base-angle of 18° and a longitudinal pitch ratio of 1.5. The resulting findings not only offers a new approach to improve the thermal performance of solar air heaters but also hints at the potential success of the GEKO model in predicting turbulent flow and heat transfer analysis.

Numerical Investigation on Improving The Effectiveness of Film Cooling Using Vortex Generators

Film cooling is an effective way for the blades to cool of an exceptionally powerful gas turbine. This process involves injecting a cooler fluid, typically air. The injected fluid forms a thin insulating layer or "film" that protecting the underlying material from thermal damage. However, due to the primary flow and film jet's interaction, a counter-rotating vortex pair is created, which causes severe jet-off and inadequate film coverage. Protrusion V-shaped and rectangular winglet vortex generators were employed In this research at the top place of the film hole to impede the counter-rotating vortex pair, in an effort to boost cooling's efficiency. Numerical simulations with Realizable k-ε were solved at a blowing ratio was between 0.5–2 and a 30° inclination angle. Results shows that vortex generators of both kinds can produce more anti-counter-rotating vortex pairs to be able to lessen the strength of the counter-rotating vortex pairs. The downwash vortices produced by the vortex generators lessen the detrimental effects of the counter-rotating vortex pair. Downwash vortices and counter-rotating vortex pair are engaged in a competitive mechanism, hence as the ratio of blowing rises, the vortex generators' favorable effects will diminish. So it was noted through this study that the best blowing ratio is (1.0). When the blowing ratio is 1.0, the results demonstrate improved film cooling performance for the flat plate. This was observed for both types of vortex generators. Specifically, the rectangular vortex generator showed this capability, with the average effectiveness of adiabatic film cooling surpassing the baseline case by 27.33%.

Effect of Upwind and Downwind Directions of Right-Trapezoidal Winglet-Vortex-Generators in a Solar-Air-Heater

Two directions of right-trapezoidal winglet vortex generators, namely, upwind and downwind directions, were numerically investigated to understand how they affect the thermo-hydraulic performance of the heat exchanger in a solar air heater. The results showed that the Nusselt number, friction factor, and thermal enhancement factor were higher when the vortex generator was installed in an upwind direction. This was because of the magnitude and the position of the airflows’ velocity. That is, faster airflows were induced in the region adjacent to the absorber plate when the vortex generator was installed in the upwind direction. As a result, high convection rates occurred and then increased the overall convective heat transfer rates of the solar air heater. Therefore, Nusselt number and thermal enhancement factor were higher. Nevertheless, the faster airflows also caused increased form drags due to vortex generator blockage, resulting in higher friction factor.

Performance enhancement of high temperature fin-and-tube heat exchanger employing winglet combined vortex generators

The fin-and-tube heat exchanger (FTHE) has the advantages of high temperature resistance, compact structure and high efficiency, and has been regarded as the optimal choice for flue gas heat transfer. In this study, the novel winglet vortex generators (VGs) are proposed for the high temperature HTHE where the flue gas with the inlet temperature of 1233 K transfers heat to the water. The effects of the combined VGs and the winglet combined VGs on the flue gas thermal–hydraulic performances are numerically studied. Furthermore, three winglet shapes including the triangular, trapezoidal and rectangular are compared. Moreover, the variations of high temperature HTHE performances with the flue gas mass flow rate are investigated. Compared to the plain fins, the surface heat flux and pressure drop of the combined VGs fins are increase by 15.8 % and 78.9 %, respectively. The designed winglets in the wake region could further reduce the area of the “teardrops” after the tube. The rectangular winglet combined VGs are decided as the best structure, which could maximally increase the surface heat flux by 11.9 kW/m2 compared to the triangular winglet combined VGs, while the pressure drop is slightly increased. Compared to the plain fins, the Nu of the rectangular winglet combined VGs is maximally increased by 16.4 and the maximum hydrothermal performance factor (HTPF) is 1.14. The optimum flue gas mass flow rate is determined as 1 g/s for the designed structures. This work can provide valuable guidance for design and modification of the high temperature HTHEs.

Multi-objective hydrothermal performance optimization of a microchannel heat sink equipped with delta winglet vortex generators using NSGA-II genetic algorithm

Microchannel heat sinks provide the solution to the ever-increasing heat flux generated from micro-electric components. In this study, performance optimization of a microchannel heat sink with delta winglet vortex generators was carried out based on the data obtained from numerical CFD simulations. A total of 192 design points were generated by altering the fluid velocity in terms of Reynolds number (Re), winglet width (Wd), length (Ld), and the angle of attachment (β) of the winglet. The Artificial Neural Network (ANN) model coupled with Non-dominated Sorting Genetic Algorithm NSGA-II was used simultaneously to minimize the friction factor and increase the Nusselt number. The ANN model predicted the output values within the error limit of 10%. The Pareto optimal front generated by the algorithm contains the input parameters in the range 982 < Re < 988, 177 μm <Ld < 233 μm, 10 μm <Wd < 25 μm, 57° <β < 64°. Decision-making methods TOPSIS, LINMAP, and Shannon entropy were employed to calculate the optimal solution from the data set and the obtained points showcased 70%, 120% and 158% surge in Nusselt number while an increase of friction factor by 35%, 109%, and 140% respectively is reported. The Performance Evaluation Criteria (PEC) values obtained from the best solutions were 1.52, 1.72, and 1.92, respectively. Furthermore, the accuracy of the optimal solutions was verified numerically. The flow and thermal field of the microchannel are also analyzed, and results showed that the angle of attachment and width of the winglet played a crucial role in the overall performance.

Numerical Study of Thermal Performance on Fin and Tube Heat Exchanger with Flat Rectangular and Sinusoidal Winglet Vortex Generators

Generation of vortices in the fin and tube heat exchanger is one of the common methods to reduce the air-side thermal resistance. This study deals with the enhancement of heat transfer in the air side using conventional rectangular and sinusoidal sine wave vortex generators. The vortex generators are placed in the downstream location of the tube in the common flow-down configurations and the range of Reynolds number is maintained about 400 to 1100. The results of the above vortex generators are compared with baseline configuration based on thermos-hydraulic criterion parameters like variation in the flow structure, variation in the temperature distribution, variation in the pressure distribution, variation in the friction factor, and overall thermal enhancement factor. Based on the comparative numerical analysis, sinusoidal and conventional rectangular winglet shows good heat transfer enhancement in that they have a large pressure loss penalty.

A comprehensive review on the effect of turbulence promoters on heat transfer augmentation of solar air heater and the evaluation of thermo-hydraulic performance using metaheuristic optimization algorithms

AbstractSolar air heaters are characterized by poor thermal performance due to limited heat transfer capability of air, thereby necessitating the need for design modifications. Among a different system performance augmentation technique, turbulence promotors are widely used owing to its effectiveness. Based on design parameters such as geometry, size, pitch and arrangement of turbulence promoters, varying levels of heat transfer increment with the pressure drop penalty is achievable. This led to the development of new designs which could offer on optimum thermo-hydraulic performance for a wide range of Reynolds number. Such research invariably requires a thorough insight of data related to various design parameters and optimal thermal–hydraulic performance range. This article provides a detailed overview of various turbulence promotor designs and their optimal thermal–hydraulic performance ranges compiled from a wide spectrum of experimental and numerical studies. Apart from outlining the general flow characteristics of each turbulator design, this study also evaluates different metaheuristic optimization algorithm such as bonobo optimization (BO), particle swarm optimization and teaching–learning-based optimization algorithm for enhancing the thermal–hydraulic performance parameter (THPP). The study shows that the BO algorithm does not exhibit local trapping due to its self-adapting nature of the optimized parameters which makes it a promising choice for THPP optimization studies in air heater applications. The extensive review also shows that the arrangement pattern of rib turbulator plays a key role in thermo-hydraulic performance augmentation. Based on the BO optimization analysis, the range of THPP is determined for the optimized geometry of turbulence promoters. In the pool of rib design, transverse prism rib, multi-V-rib, multi-V-shaped rib with staggered rib, sinewave-shaped rib with gap and S-shaped ribs exhibits an optimal THPP range of 2.05–3.32, 2.43–2.94, 3.00–3.61, 1.58–3.40 and 2.05–3.74, respectively. Other turbulence promotor designs such as winglet vortex generator, dimple protrusion in arc shape and multi-V-baffles exhibits optimal THPP range of 1.95–2.2, 2.44–3.68 and 1.75–2.01, respectively. At the end, the study proposes key research gaps such as the use of combined ribs and vortex generators and discrete fin arrays of different geometry as future scope of research. Graphical abstract

Investigation of local flow and heat transfer of supercritical LNG in airfoil channels with different vortex generators using field synergy principle

Vortex generators（VGs） have gained significant attention as a potential technology for enhancing heat transfer. This study introduces a novel delta airfoil VG with the objective of improving the heat transfer efficiency of heat exchangers. The overall heat transfer performance of four types of printed circuit heat exchanger (PCHE) channels is evaluated using three-dimensional numerical analysis in this paper. These channels comprise of two VGs with different shapes and installations, along with NACA0024 airfoil fins. The delta winglet VG (DWVG), the delta airfoil VG (DAVG), and the delta airfoil staggered VG (DASVG) are the VGs used in the three PCHE channel configurations. The performance of the four PCHE flow channels is assessed using the dimensionless thermal enhancement factor (TEF). To investigate and explain the interaction between VGs and flow structure distribution as well as heat transfer, the secondary flow number Se and the field synergy principle are employed. The results show that the local field synergy angle of the channel with VGs is smaller than that of the non-VG baseline case, indicating the best enhanced heat transfer in the pseudo-critical region. Among the four cases, the DAVG exhibits the best hydrothermal performance, and the local heat transfer coefficient can be increased up to 120%, which aligns with the interpretation of the field synergy principle.

Effects of the position and perforation parameters of the delta winglet vortex generators on flow and heat transfer in minichannels

Minichannel with delta winglet vortices generator (VG) is widely used in heat exchangers. However, there is limited research in the literature on using VG with holes in opposite wall surfaces within a channel, and there are few reports on whether the use of VG with holes in minichannel will necessarily enhance heat transfer. In this work, we consider two different VG arrangements placed on opposite walls of a channel and three parameters for opening hole diameter (0.05, 0.15, and 0.25mm). Additionally, three different pitch values (15mm∼30mm∼45mm) are examined. Under a Reynolds (Re) number ranging from 3000 to 5500, the influence of VGs placement and hole parameters on the flow and heat transfer performance through calculations of parameters such as Nusselt number (Nu), friction coefficient (f), and thermal performance factor (TPF) are evaluated. Furthermore, the vortex structures are checked using the Q method and secondary vortex strength (Se). The results are shown to demonstrate that different VG placements mainly affect the main longitudinal vortices (MLVs), secondary longitudinal vortices (SLVs), and induced corner vortices (ICVs) structures downstream of the VGs. As the opening area increases, the shape of both vortices downstream of the VGs is significantly suppressed due to the generation of a jet flow, and the ICVs may even disappear (r=0.25mm). Case 1 (the right angle of the triangular wing is close to the center of the channel) has a larger TPF value. The opening of the hole reduces the heat transfer performance compared to the non-punched case, and their Nu number and f value are reduced by 0.2%−6.9% and 0.1%−8.3%, respectively. Case 1 obtained the maximum TPF value at Re=3000, which is 1.15, and P=15mm.

Numerical simulation study of enhanced convective heat transfer in the tube based on winglet vortex generator

In order to enhance the heat transfer effect and improve the energy utilization efficiency of the circular tube under turbulent flow, rhombic and triangular winglet vortex generators are proposed on the basis of rectangular winglet vortex generator. The effects of three vortex generators on flow and heat transfer in the tube are investigated by numerical simulations. The results indicate that, the rectangular and triangular winglets generate two pairs of longitudinal vortices and the triangular winglets generate four pairs of longitudinal vortices due to additional shrink-age regions. The multiple longitudinal vortices increase the mixing between the fluids, raise the temperature in the central region of the tube, and enhance the heat transfer effect. Furthermore, the triangular winglet enhanced tube has the largest direct flow area and the least effect on resistance. The triangular winglet enhanced tube had the best comprehensive performance, followed by the rhombic winglet enhanced tube, and finally, the rectangular winglet enhanced tube. The performance evaluation criterion reached 1.04-1.13, 1.05-1.15, and 1.08-1.21 for the three enhanced tubes in the given flow rate interval. In addition, the effect of inclination angle on the triangular winglet enhanced tube was further investigated, and the results show that the best comprehensive performance of enhanced heat transfer is achieved at an inclination angle of 45?, with a maximum performance evaluation criterion of 1.25.

Numerical simulation study of enhanced convective heat transfer in the tube based on winglet vortex generator

In order to enhance the heat transfer effect and improve the energy utilization efficiency of the circular tube under turbulent flow, rhombic and triangular winglet vortex generators are proposed on the basis of rectangular winglet vortex generator. The effects of three vortex generators on flow and heat transfer in the tube are investigated by numerical simulations. The results indicate that, the rectangular and triangular winglets generate two pairs of longitudinal vortices and the triangular winglets generate four pairs of longitudinal vortices due to additional shrinkage regions. The multiple longitudinal vortices increase the mixing between the fluids, raise the temperature in the central region of the tube, and enhance the heat transfer effect. Furthermore, the triangular winglet enhanced tube has the largest direct flow area and the least effect on resistance. The triangular winglet enhanced tube had the best comprehensive performance, followed by the rhombic winglet enhanced tube, and finally, the rectangular winglet enhanced tube. The performance evaluation criterion (PEC) reached 1.04-1.13, 1.05-1.15, and 1.08-1.21 for the three enhanced tubes in the given flow rate interval. In addition, the effect of inclination angle on the triangular winglet enhanced tube was further investigated, and the results show that the best comprehensive performance of enhanced heat transfer is achieved at an inclination angle of 45?, with a maximum PEC of 1.25.

Numerical study of the vortex generators effects in a corrugated channel for turbulent flow

Vortex Generators (VGs) are one of many techniques used to improve the efficiency of heat exchangers. In this paper, we will investigate in a numerical study a rectangular winglet and a long winglet VGs inside a corrugated channel with a change of Rynolds number from 5000 to 17500. The role of VGs is to manupilate flow, which increases the Nusselt number (Nu) and increases the friction coefficient, which are considered disadvantages. For that, we calculate the thermal performance coefficient PEC to see if VGs give us more heat compared to what we will lose from friction, and the results show a good PEC greater than 1, and comparing between rectangular and long VGs, we have almost the same results with a small difference in NU for rectangular VGs being higher than long VGs, and the coefficient of friction is smaller, which means we are battered. The results are discussed in detail in this paper.

Power consumption and thermal performance of tube employing punched delta winglets

The method of enhancing heat transfer (HT) by combining jets and main longitudinal vortex (MLV) had been proposed and proven effective. Based on this method, this article further explored the interference effect of VG structure on jets, MLVs, and other forms of vortices, as well as the corresponding HT mechanism. The punched delta winglet vortex generators (PDWVGs) applied in this work had three inclined angles (α=30°,60°,90°), three numbers (N=2,4,6), and three pitch ratios (PR=4.89,3.27,1.63). The secondary vortices number (Se values were used to measure the strength and position of different vortices, and the field synergy number (Fc) was also applied to measure the underlying causes of HT rate. The results confirmed that MLVs (induced by PDWVGs in core-flow region) were created, which improved the mixing rate of the air. It was worth mentioning that the structure of MLVs and jets was different at different α values, specifically when α>30°, the jets would carry away heat from the wall surface and would also collide with the reflux MLVs, suppressing the further formation of the reflux region. The Se values of different cases clearly demonstrate the morphology and intensity of mixed vortices. Within the studied parameter range, the biggest TEFof 1.29 was observed at N = 2, PR = 1.63, α = 30° at Re=9090.

Heat Transfer Augmentation in Fin and Tube Heat Exchanger Embedded with Vortex Generators

The aim of this study is to investigate experimentally turbulent flow around tube by using multi–shapes of winglet vortex generators mounted behind the tube at different angles of attack, in order to investigate the effect of winglet on heat transfer and pressure drop of fin and tube heat exchanger placed inside a rectangular duct with Reynolds numbers (Re) ranging from (19000) to (49000). Fin-and-tube heat exchangers are frequently employed in a variety of industries, including power systems and air conditioning. The heating element inside the tube receives a power source ranging from (10W) to (40W). In these studies, vortex generators of the triangular and rectangular types are installed at various angles of attack (45° and 60°) on the fin surface behind the tube. The findings demonstrate that depending on the form and angle of attack of the winglets, utilizing winglet pairs has an impact on the heat transfer coefficient and friction factor relative to other designs. With increasing angle of attack, the friction factor and heat transfer coefficient rise. The optimal design for improving heat transfer is the rectangular type vortex generator, whereas the triangular type produces the least amount of heat transfer. The rectangular style of duct has the greatest pressure drop. For rectangular and triangular heat exchangers, respectively, the average Nusselt number is increased by 19% and 12%. The average Nusselt number of a fin and tube heat exchanger is increased by (16.7-17.8%) % for the rectangular type and by (9.3-10.6%) % for the triangular type at an angle of attack (β=60°) compared to (without winglet) case for Reynolds number ranging between (19000-49000), where the triangle type gives the least amount of heat transfer compared to other shapes.

Thermohydraulic performance study of the effect of winglet inserts and a corrugated wall in a rectangular channel

This numerical study investigates the enhancement of heat transfer and pressure drop characteristics in rectangular channels with transverse corrugations and longitudinal winglet vortex generators. Numerical simulations cover a range of Reynolds numbers (Re) (5000–20000) using channels with uniform wall heat flux and fixed wavelength. The study evaluates the influence of geometrical parameters (corrugated channel amplitude and winglet length) on flow and temperature characteristics, average Nusselt number (Nu), and pressure drop. Corrugated channels alone create stationary transverse vortices that impede heat transfer. However, integrating winglet vortex generators introduces beneficial longitudinal vortices, disrupting stationary vortices, perturbing the thermal boundary layer, enhancing near-wall turbulence, and improving fluid mixing and heat transfer compared to smooth and corrugated channels. At Reynolds number (Re)20,000, corrugated channels with winglets exhibit 167.7 % and 61.8 % higher Nusselt numbers compared to smooth and corrugated channels, respectively. However, this enhanced heat transfer accompanies increased pressure drop. Both heat transfer and pressure drop rise with higher Reynolds numbers (Re), corrugation amplitude, and winglet length. This study provides insights into heat transfer mechanisms in corrugated channels and the potential for improvement through winglet vortex generators.

Impact of a new envelope winglet vortex generator on engine power and thermoelectric waste heat recovery

Impact of a new envelope winglet vortex generator on engine power and thermoelectric waste heat recovery

Analysis of the thermal improvement of plate fin-tube heat exchanger with straight and curved rectangular winglet vortex generators

A novel combination of curved and straight rectangular winglet vortex generator (RWVG) pairs was arranged in a common-flow-up (CFU) configuration on plate fins for enhancing the comprehensive performance of the fin-tube heat exchanger. The effects of RWVGs were compared with those of non-RWVGs for flow streamline, temperature distribution, and pressure field. Then the thermohydraulic performance and the comprehensive performance were numerically investigated among the cases with varied locations and sizes of RWVGs. The results revealed that j for all cases with RWVGs was higher than non-RWVGs and the values of JF were greater than 1.0 for all cases except for case 4. Especially, apparent improvements in heat transfer characteristics and comprehensive performance were observed with the novel combination. Furthermore, it was found that the appropriate location and size of RWVGs were able to influence the thermohydraulic characteristic positively. The curved RWVGs with a smaller offset showed better comprehensive performance, and the larger attack angle of the straight RWVGs was accompanied by a higher heat transfer intensity and a greater flowing drag force. Moreover, the curved RWVGs with a larger arc angle performed better in the comprehensive performance, and the length of the straight RWVGs was larger and JF smaller.