Delta Winglet Research Articles

Experimental Investigation on Vortex Generator's Distance From Film Cooling Hole

Abstract The effects of vortex generator distance from film cooling hole on increasing gas turbine blade film cooling efficiency have been studied experimentally. The technique of infrared (IR) thermography has been implemented to study the temperature field. The diameter of the film cooling hole and the cross-flow velocity define the Reynolds number, which is fixed at 2369. There are now three different jet to cross-flow blowing ratio adjustments: 0.5, 1.0, and 1.5. Three different vortex generator distance from film cooling hole have been studied experimentally to increase the gas turbine blade film cooling efficiency. It has been shown that lowest distance among vortex generator distance and film cooling hole, yields better film cooling efficiency. Overall, the delta winglet pair with lowest distance between vortex generator distance and film cooling hole outperforms the higher distance because of the generation of secondary longitudinal vortices that completely destroy counter rotating vortex structures because their rotational tendency is opposite to that of the counter rotating vortex pair (CRVP).

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.

Effect of Vortex Generator on Gas Turbine Blade Cooling

The current numerical study suggests using a vortex generator to lessen the consequences of a counter-rotating vortex pair. For this inquiry, the delta winglet pair in the common-flow-down arrangement is selected. A suitable model for turbulence is examined. The x, y, and z vorticity is studied. Additionally, the effect of variations in turbulent kinetic energy is examined. The outcome is contrasted with the reference scenario. Employing the k-omega SST turbulence model and the commercial code FLUENT, numerical analysis is accomplished.

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.

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.

Numerical Inspection of location, density ratio and turbulent kinetic energy of vortex generator in gas turbine blade film cooling application

Abstract Present numerical investigation proposes to mitigate the effects of Counter rotating vortex pair by employing vortex generator. The common-flow-down arrangement of delta winglet pair is preferred for this investigation. The investigation of suitable turbulence model has been studied. Numerical simulation has been carried out to investigate the effect of placement of vortex generator on the characteristics of film cooling effectiveness. Vortex generator located at upstream, downstream and both before, after and both before, after film cooling hole respectively. Result indicates that Vortex generator, located at up-stream of circular film cooling hole will yield better effectiveness. Reynolds number based on free stream velocity and film cooling-hole dimension is kept at 17000. Moreover consequence, in variation of blowing ratio (M = 0.5, 1, 1.5), density ratio (DR = 0.5, 1, 2), secondary flow velocity or jet velocity (uj) and T.K.E on cooling effectiveness has been investigated. Result shows that increment in M, uj and T.K.E responsible for decrement in cooling effectiveness. The results are compared with baseline case. It has been observed that numerical investigation implementing FLUENT commercial code adopting the k-omega SST turbulence model perform better.

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.

Heat transfer enhancement mechanism of elliptical cylinder for minichannels with delta winglet longitudinal vortex generators

In order to improve the heat transfer performance in the minichannel with delta winglet longitudinal vortex generators and obtain the heat transfer enhancement mechanism, the flow and heat transfer of four basic models (CFD-I, CFD-V, CFU-I and CFU-V configurations) and four enhanced models with elliptical cylinders are numerically simulated in the range of Reynolds number from 2500 to 10,000. The friction factor, Nusselt number and thermal performance factor are evaluated, and the secondary flow intensity and entropy generation rate are analyzed. The main conclusions are as follows: compared with the basic models, the Nusselt number increase by 8.4–14.1 %, 6.1–12.0 %, −1.9-5.0 % and 11.0–14.9 % respectively after adding the elliptical cylinders, and the thermal performance factor of these four models with elliptical cylinders are within 1.05–1.25, 1.00–1.13, 0.97–1.16 and 1.03–1.22, respectively. Compared with the smooth channel, the Nusselt number of CFD-V and CFU-I configurations with elliptical cylinders increased by up to 61 % and 63 %, respectively, and the overall thermal performance increased by up to 25 % and 22 %, respectively. These two configurations are recommended because they make full use of the fluid accelerated by the elliptical cylinder and effectively improve the strength and influence range of the longitudinal vortexes.

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.

Numerical analysis and optimization of the heat transfer enhancement from the heat transfer fluid side in a shell-and-tube latent heat thermal energy storage unit: Application to buildings thermal comfort improvement

This study investigates the impact of enhancing the convective heat transfer on the Heat Transfer Fluid (HTF) side by passive flow manipulation on the melting and solidifying kinetics of a Phase Change Material (PCM) in a shell-and-tube Latent Heat Thermal Energy Storage (LHTES) unit. The PCM used is PureTemp 23 (PT23), a commercial bio-sourced product. The targeted application is the development of a LHTES unit for improving the thermal comfort in buildings through a combined heating and cooling approach. The study is carried out using the commercial code STARCCM+ and the enthalpy-porosity method, with appropriate implementation of the buoyancy source term. The numerical approach used for phase change modeling has been validated by comparisons with reference data from the open literature. Delta Wing pairs (DWg) and Delta Winglet pairs (DWt) vortex generators (VGs), were first inserted into the tube in which the HTF flows. Parametric analysis on the aspect ratio, position, and VGs number were performed, and optimization was done on the attack and rolling angles. The Performance Evaluation Criteria (PEC) index, which takes into account the heat transfer enhancement achieved and the related pressure losses, was used as an assessment criterion to evaluate the heat transfer augmentation of the studied enhanced tube with VGs. The results show that maxima can be reached for the different parametric studies carried out. While PEC increases with the attack angle until a maximum beyond which it decreases, it decreases consistently with the rolling angle. Once the enhanced optimal tube equipped with a shell containing the PCM, the results of the detailed study made on the kinetics for charging and discharging period of the enhanced LHTES unit reveal important gain for the storage unit. The heat transfer enhancement achieved result into more than 110 % increase in the PCM's melting/solidifying kinetics in the shell, thanks to an increase in the heat duty exchanged between the HTF and the PCM, leading to a considerable reduction of complete melting/solidification time. It was observed that the enhanced and optimized LHTES unit developed in the present study has a huge potential for improving buildings seasonal thermal comfort.

Effect of Vortex Generator Placement and Nanofluids on Channel Flow Heat Transfer

In this research, an attempt has been made to enhance the heat transfer for a plate-fin heat exchanger with the new arrangement of classic delta winglets used for vortex generators and compared the same with the existing literature. The computational domains are developed by dislocating delta winglets from their original position, so there is no additional pressure loss with flow geometry. All the flow domains are analyzed by computing the 3D Reynolds averaged Navier–Stokes equations using ANSYS Fluent. Two different working fluids are considered one is water and nanofluids (water with Aluminum oxide). Heat transfer characteristics are analyzed for different placements of winglets for both water and nanofluids. The plate-fin heat exchanger’s performance has been optimized with the optimum location of winglets and nanofluids from the analysis of numerical results. For the case of 0% nanofluids at 300 Reynolds number, Case 3 Nusselt number has been increased by 23.2% with a decrease in pressure drop of 17.7% with the dislocation of one winglet. It represents the enhancement of heat transfer.

Surrogate-based optimization of the attack and inclination angles of a delta winglet pair vortex generator in turbulent channel flow

Vortex generators (VGs) have been extensively studied and utilized in multifunctional heat exchangers/reactors due to their remarkable ability to create coherent flow structures and streamwise vortices. These characteristics significantly enhance the mixing and heat transfer performance in laminar and turbulent flow regimes. With the advancement of computational power, VG shape optimization has become feasible, leading to the discovery of various optimized shapes in the literature for different Reynolds numbers. In this paper, the response surface polynomial method is employed as a surrogate model to optimize the angle of attack and inclination angle of a delta winglet VG at a Reynolds number of 4,600. The potential applications of these optimized designs are diverse, particularly in scenarios that require cooling or heating. Some examples include photovoltaic (PV) panel cooling, waste heat recovery in hybrid PV/solar water heating systems, energy-efficient HVAC systems, and thermal management in electric vehicles. To achieve this objective, Computational Fluid Dynamics (CFD) simulations are conducted to compute the thermal performance factor of each VG design at various values of attack and inclination angles. By enhancing mixing and heat transfer capabilities, this design can have a substantial impact on various renewable energy applications, contributing to a greener and more sustainable future. The highest thermal enhancement factor of 1.15 is found to be achieved for an inclination angle of −45° and an angle of attack of 35°. This means that optimized VG enhances heat transfer by 15% compared to empty channel flow, while maintaining the same pumping power.

Performance enhancement of fin and tube heat exchanger employing curved delta winglet vortex generator with circular punched holes

The generation of vortices has recently gained attention as a potential passive technique for improving air-side heat transfer in a fin and tube heat exchanger. This study proposes novel configurations of a curved delta winglet vortex generator (CDWVG) with and without circular holes to improve heat transfer in FTHEs. The present study utilizes a three-dimensional numerical analysis to investigate the thermal-hydraulic performance analysis of fin and tube heat exchanger (FTHE) with curved delta winglet vortex generators (CDWVG) with or without circular holes, operating across a wide Reynolds number range (i.e., from 400 to 2000). In addition to being arranged in vertical and horizontal configurations, the CDWVGs are oriented in the same way as the flow direction. Therefore, the pressure distribution, temperature distribution, and flow structure distribution of an FTHE with a four-in-line circular tube configuration are analyzed and compared between FTHE without vortex generator (VG) and five different configurations of CDWVG (i.e., CDWVG without hole, CDWVG with 1 hole, CDWVG with 2 holes, CDWVG with 3 holes and CDWVG with 6 holes). The pressure drop (ΔP), London area goodness factor (LAGF) (j/f), Nusselt number (Nu), and Colburn factor (j) are also used to evaluate the thermo-hydraulic performance of FTHE. The FHTE performance with CDWVGs can be affected by the number of punched holes, which is evaluated using a dimensionless number including Performance Evaluation Criteria (PEC), Colburn factor, etc. The thermo-hydraulic efficiency of the FTHE is improved significantly by using CDWVGs with circular punched holes. Nusselt number decreases across all the VG configurations (i.e., CDWVG without hole, CDWVG with 1 hole, CDWVG with 2 holes, CDWVG with 3 holes, and CDWVG with 6 holes) due to the lower flow resistance. Compared to other CDWVG configurations, the 6-hole configuration of CDWVG is the most effective. The Nusselt number of CDWVG with 6 holes increases by 77.25% and 42.51% at Reynolds numbers of 400 and 2000, with respect to fin and tube heat exchangers without vortex generator, respectively. On the other hand, friction is decreased by 5.11%. Therefore, when considering the London area goodness factor, CDWVG with six holes is found to be superior to other CDWVG configurations.

ANALISA PERFORMA HEAT EXCHANGER DENGAN PENAMBAHAN VORTEX GENERATOR TIPE DELTA WING DAN DELTA WINGLET TAPE INSERT GUNA MENGATASI ICING PADA KARBURATOR PISTON ENGINE

The simple simulation tool of the heat exchanger has a limitation, that is, when the heat transfer process cannot be analyzed directly, and the flow motion cannot be observed. Therefore it can be solved by the CFD method. The purpose of this study is to provide observable visual images. In this simulation, it uses a tube given a vortex generator with delta variations adding angles, each of which is given a constant inlet velocity, inlet temperature, and heatflux input values. Each angle is given a value of 200, 400, 600. This study aims to obtain a vortex generator with the best angular variation. From the research that has been carried out, it shows that the addition of delta provides a difference in the results of each specimen tested, the addition of a delta winglet with the addition of an angle of 400 is produced to have the best heat transfer coefficient, it is shown at a low temperature difference (ΔT). Analysis of the results of a low temperature difference (ΔT) means that the specimen performed good heat transfer performance.

Exergy and sustainability analysis of a solar heat collector with wavy delta winglets as turbulent promoters: A numerical analysis

This numerical study aims to determine the exergy analysis for a modified solar heat collector (SHC) having wavy delta winglets as turbulent promoters. These winglets disrupt the viscous layer to improve the heat transfer rate from the heat-absorbing surface to the fluid medium in the rectangular channel. The analysis considers following parameters: the relative longitudinal pitch (P/H), number of waves (φ), and flow angle of attack (α0) and flow Reynolds number range of 4000–18000. The maximum exergy efficiency of 29.18% is achieved with a longitudinal pitch of 5, an angle of attack of 60°, and a relative number of waves of 5. To evaluate the system's feasibility and sustainability, the study uses a Sustainability Index (SI), which reflects the system's Waste Energy Ratio (WER) and Improvement Potential (IP). This assessment helps identify opportunities for improvement in the thermal system.

Heat transfer enhancement and flow characteristics of internal cooling channels with slit vortex generators

Vortex generators can boost heat transfer performance greatly, although they are always linked with significant pressure drops. In this article, to reduce the pressure drop while improving the thermal efficiency simultaneously, traditional delta winglet pair vortex generators (DWPVG) with slits are installed in the rectangular channel. Besides, the effects of slits on DWPVG on pressure drops and heat transfer performances for different Reynolds numbers are studied. To reveal the fluid flow characteristics, three-dimensional calculations using a confirmed turbulence model are undertaken and the underlying thermo-fluid processes are exposed for the various investigated cases. To reveal the overall thermal performance of different cases, two overall thermal performance factors Nu ave/Nu 0/(f/f 0) and Nu ave/Nu 0/(f/f 0)1/3 are used. The findings suggest that when the fluid flows through slits, induced vortices are located closer to the bottom surface, generating an improvement of the local Nusselt number behind DWPVG. Furthermore, DWPVG with slits can decrease the pressure drop, but also make the local thermal efficiency improve in the channel with a high blocking ratio. Moreover, the increase in the overall thermal performance of the slit DWPVG channel with a high blocking ratio is enlarged with the Reynolds number raise. Besides, the highest heat transfer enhancement is provided by opening slits on five DWPVGs in the rectangular channel.

Improvement of Plate-Fin Heat Exchanger Performance with Assistance of Various Types of Vortex Generator

A 3-dimensional incompressible laminar flow and heat-transfer in a plate-fin heat exchanger (PFHE) where investigated numerically in this article. The influence of mounting a longitudinal vortex generator (LVG) on the offset rectangular-triangular fin (ORT) in the PFHE, on thermal and hydro-dynamic fields are presented. The novelty of this study is by attaching a LVG to an offset strip fin (OSF) surface. The cases of study for the PFHE are established, by using a built-in rectangular winglet pair type RWP longitudinal vortex generator carried out and fitted on this fin to improve the convective heat transfer of the (ORT) fin while minimizing pressure loss. The upper and lower plates are exposed to constant heat flux and the working fluid is air where chosen under a laminar range of RE (600 to 1400). The laminar flow and heat-transfer are governed by continuity, momentum and energy equations. ANSYS FLUENT (2021 R1) is used to get the numerical results, based on the finite volume method. The performance of the VG is assessed for an optimum winglet attack angle (45°), as well as by modifying the geometrical size parameters, namely the height and placement (L) of the RWP LVG. The result shows that the Nusselt number reaches its optimum enhancement values by using a common flow up CFU built-in rectangular winglet pair type RWP VG with a height and entrance length of (h=1.25mm, L=0.5mm), by 22.23% as compared with base case configuration (ORT). Finally, a two more LVG are tested with the optimum conditions of the RWP, which they are a delta winglet pair (DWP) and trapezoidal winglet pair (TWP). In addition, the temperature fields for the primary and secondary flows were shown in contour and streamline diagrams

Effects of the configuration of the delta winglet longitudinal vortex generators and channel height on flow and heat transfer in minichannels

Minichannels with the delta winglet longitudinal vortex generators (LVGs) is commonly used in the heat exchanger. However, there are few studies on the configuration of LVGs on the opposite walls and the large aspect ratio of the channel in the existing literature. In this paper, five LVGs configurations including arrangement on the opposite walls are considered, and four channel heights (1, 2, 4 and 8 mm) are considered to achieve a wide coverage of the channel aspect ratio (0.125–1). In the Reynolds number range of 3000 to 18,000, the effects of LVGs configuration and channel height on flow and heat transfer are obtained by evaluating parameters such as friction factor, Nusselt number, thermal performance factor (TPF), field synergy and frictional entropy generation rate and analyzing the vortex structure displayed by Ω method. The results show that the LVGs configuration and channel height mainly affect the main vortex behavior downstream of LVGs, but have little effect on the vortex structure near LVGs. The Mixed configuration at H = 1 mm and the CFU1 configuration at H = 2 mm have better heat transfer enhancement performance, and their Nusselt numbers are increased by 28–35% and 27–33%, respectively, compared with smooth channels. In addition, the configuration selection aiming at high overall performance under different conditions is given.

The Use of a Vortex Generator for the Efficient Cooling of Lithium-Ion Batteries in Hybrid Electric Vehicles

High heat flux dissipation from the Lithium-ion battery pack of hybrid electric vehicles is one of the major concerns in the automotive sector, since it directly affects the performance and it may also lead to permanent failure. Among various thermal management systems, forced air cooling is most favorable due to its light weight, compactness, lower cost, and design flexibility. In the present work, a battery thermal management system with the two types of vortex generator in the coolant passage has been used to enhance the performance. A numerical model has been developed in commercial code to investigate the performance of the delta winglet and circular protrusion type vortex generator. Apart from that, both types of vortex generator have been compared in terms of various parameters such as pressure drop, weight, and maximum temperature. From the results of the simulation, it has been observed that both vortex generators performed better at the attack angle of 30° in comparison to the attack angles of 45° and 60°. Furthermore, it has also been found that the cooling system with protrusion as the vortex generator has performed better in terms of thermos-hydraulic performance compared to the cooling system with the delta winglet vortex generator. In addition to that, the protruded system is lighter in weight compared to both the plain and delta winglet systems, and is recommended.

Multi-objective optimization of a tubular heat exchanger enhanced with delta winglet vortex generator and nanofluid using a hybrid CFD-SVR method

The present study improves the thermal-hydraulic performance of a circular tube equipped with a delta winglet vortex generator by providing a numerical model, investigating the effect of two additional parameters, and developing a support vector regression (SVR) for prediction and optimization. The additional parameters are the angle of attack and SiO2 concentration, while the data on the variation of thermohydraulic parameters with pitch and blockage is already available in the literature. The boundary layer disruption and swirling flow caused by the delta winglet result in heat transfer enhancement. The presence of such inserts also increases the pressure drop in the heat exchanger. The nanofluid further enhances heat transfer by boosting the thermophysical properties of the fluid. The hybrid method, CFD-SVR, is carried out for turbulent water flow at Reynolds numbers ranging from 4200 to 16200. The delta winglets are in pair arrangement with ten angles of attack from 25∘ to 70∘ with 5∘ increments. The addition of SiO2 with volumetric concentrations varies from φ=0 to 0.5% has been explored. The diameter of the tube (D) is 50 mm, while the pitch ratio (P/D) and blockage ratio (B/D) vary from 1 to 3 and 0.1 to 0.2, respectively. Finally, the data of this study and the previously published experimental data were fed into an SVR to find the best possible arrangement of delta winglet for a tubular heat exchanger. The highest achieved thermal enhancement factor (TEF) was found to be 2.18 with α = 25°, PR = 0.83, BR = 0.13, and φ = 0.5% at the least Re number.