Winglet Vortex Generators Research Articles

Performance Enhancement of Finned Tube Heat Exchanger using New Vortex Generator

The present work aims to investigate a performance enhancement in an H-shaped finned tube heat exchanger using a new design of winglet vortex generator. The new design has an aerodynamic shape that reduces the pressure drop and enhances the heat transfer, resulting into an improvement in the overall thermo-hydraulic performance. A three-dimensional model is developed using ANSYS fluent to carry out simulations for Reynolds number varying between 5000 ≤ Re ≤ 11000 and to predict the net enhancement in the heat exchanger performance. The validation of the model is done using experimentally developed correlations of dimensionless pressure drop and heat transfer characteristics. Comparative results for the finned tube heat exchanger with and without vortex generator are presented. Results indicate a significant enhancement in the heat transfer characteristics of the finned tube heat exchanger with the new design of vortex generator. Volume goodness ratio and Colburn j-factor found to be 19.63% and 30.33% higher than the baseline finned tube heat exchanger without any vortex generator.

Overall cooling performance evaluation for film cooling with different winglet pairs vortex generators

Previous studies have shown that the film cooling effectiveness can be improved by using a winglet pair vortex generator upstream or downstream of the film hole, but these studies merely focused on rectangular and delta winglet pairs and the overall performance evaluation has no heat transfer results. In this study, the overall film cooling performance of a cylindrical film hole with four types of winglet vortex generators upstream of the film hole was numerically investigated. The numerical simulation with the realizable k-ε turbulence model was performed by commercial software Fluent, solving steady Reynolds-average Navier-Stokes equations. The film cooling effectiveness with vortex generators is one or more times higher than that without the vortex generators owing to the downwash vortices generated by the vortex generators. The downwash vortices mitigate the negative effect of the counter-rotating vortex pair. There is a competitive mechanism between the downwash vortices and the counter-rotating vortex pair, so the beneficial effect of the vortex generators will weaken with the increase of the blowing ratio. The heat transfer coefficient of film cooling with vortex generators is higher, with a maximum augmentation of 11.45%. The heat transfer distributions of different vortex generator configurations are similar. Results prove that the case with the rectangular winglet pair vortex generator is the optimal configuration since it provides 0.08–0.29 higher net heat flux reduction than the case without the vortex generators.

Heat Transfer Characteristic on Wing Pairs Vortex Generator using 3D Simulation of Computational Fluid Dynamic

Vortex generators are addition surface that can increase heat transfer area and change the fluid flow characteristics of the working fluid to increase heat transfer coefficient. The use of vortex generators produces longitudinal vortices that can increase the heat transfer performance because of the low pressure behind vortex generators. This investigation used delta winglet vortex generator that was combined with rectangular vortex generator to Reynold numbers ranging 6,000 to 10,000. The parameters of Nusselt number, friction factor, velocity vector and temperature distribution will be evaluated.

Numerical Analysis on Thermohydraulic Performance of the Tube Inserted with Rectangular Winglet Vortex Generators

The aim of this design was to improve the heat transfer performance significantly due to larger turbulent region and much vortices formed by tube inserted. In this article, the BSL k-ω model was chosen as turbulence model to simulate the thermohydraulic performance of the proposed tubes inserted with rectangular winglet vortex generators (RWVGs) when the Re was set as 5000 to 15,000. The reliability of the simulation results was obtained by comparing with the empirical formulas and experimental results. By means of numerical simulation, the influence mechanism of geometric parameters of RWVGs on thermal-hydraulic performance in tubes was analyzed. And the impact of three configurational parameters on the thermal performance was studied, namely the angle α, the height H and the number N of the RWVGs, respectively. The results revealed that the capacity of heat transfer in tubes with RWVG inserts was obviously larger than that in ordinary circular tube. In addition, it could be seen from the results that both Nu and f increased with the increase of H and N. At the same time, the case of α = 135° showed the greatest enhancement of thermal performance than the case of α = 45° and α = 90°.The PEC achieved the highest value of 1.23 when the height H of RWVG was 0.7 mm, the number N was 20, and angle α was 135°.

Novel self-join winglet vortex generators for enhanced heat transfer of turbulent airflow in round tubes

Novel self-join winglet vortex generators (SWVGs) consisting of multiple pairs of connected V-shaped rectangular winglets were put forward for enhanced heat transfer of turbulent airflow in round tubes. Numerical results firstly confirmed the generation of longitudinal swirl flows, which improved the air mixing and reduced the synergy angle between flow and thermal fields in the tube. Besides, increasing the winglets' included angle (α) and height ratio (HR) resulted in more intense swirl flows and uniform temperature distributions. Additive manufacturing was applied to fabricate the vortex generators using nylon, and experimental tests were carried out. The results showed that the Nusselt number ratio was 1.50–3.49 over the smooth tube, demonstrating the high capability for enhanced heat transfer of the proposed SWVGs. However, pressure loss was accompanied meanwhile. The overall thermal performance in terms of thermal enhancement factor displayed a decreasing tendency with the Reynolds number. The maximum thermal enhancement factor value of 1.27 was found at HR = 0.05 and α = 120°. In addition, the empirical correlations for friction factor and Nusselt number regarding α, HR, and Reynolds number were achieved by nonlinear regression to reference industrial applications.

Comparison of Different Fin and Tube Compact Heat Exchanger with Longitudinal Vortex Generator in CFU-CFD Configurations

Over the last decades several studies have searched for improved Fin and Tube Heat Exchanger (FTHE) designs capable of providing the best thermo-hydraulic performance. The present study aims at quantifying and comparing the thermo-hydraulic performance of different FTHE configurations. Six different designs were analyzed. The first FTHE consisted of an in-line circular tube arrangement and the last one was a FTHE with staggered oval tube with two pairs of Delta Winglet Vortex Generators (DWVG) in common flow up–common flow down (CFU-CFD) configuration. The best performance was obtained using DWVG in CFU-CFD orientation. This configuration enabled a 90% increase of the thermal performance factor when compared with the first case, using only two pairs of vortex generator´s per tube.

Experimental study on the heat transfer enhancement in a rectangular channel with curved winglets

ABSTRACT Effects of the curved winglet vortex generator inserts (CWVGs) on the forced convection heat transfer, friction factor, and performance evaluation criteria (PEC) interior flow were experimentally examined in this work. The CWVGs manufactured in CNC from aluminum 6061 material were used as the expanded finned surface with different attack angles (α) of 0°, 30°, and 60°. In the study, air was used as the fluid. The experiments were realized in the Reynolds number ranging from 6000 to 20000. The results showed that the CWVG insert in a rectangular channel ensured significantly higher Nusselt number than that of the channel without the insert through friction factor that was also increased. The Nusselt number and friction factor increased with the increase in the attack angle (α) of CWVG insert. The heat transfer enhancement by the CWVGs with attack angle of 0°, 30°, and 60° ensured higher than that of the plain tube in the range of 217.39–291.30%, 260.86–465.21%, and 278.26–476.08%, respectively. The friction factors in the inner rectangular channel produced by the CWVGs with attack angle of 0°, 30° and 60°, were about 8.93–10.33, 10.66–14.16, and 14.96–19.13 times above the plain tube, respectively. The performance evaluation criteria (PEC) for CWVGs with attack angle of 0°, 30°, and 60° were in the range of 1.22–1.78, 1.28–1.86, and 1.32–1.89, respectively.

Effect of perforated concave delta winglet vortex generators on heat transfer and flow resistance through the heated tubes in the channel

ABSTRACT This study focuses on improving heat transfer from the surface of heated tubes to airflow in the channel. Perforated concave delta winglet vortex generators, which have not been used in previous studies, were implemented in this study to increase the heat transfer rate. In this experimental study, the comparison of perforated concave delta winglet and perforated delta winglet was investigated in terms of increased heat transfer from a heated six-tube surface to the flow in a rectangular channel. The experimental results indicated that the use of perforated concave delta winglet vortex generators could increase the heat transfer rate of 46.3% toward the baseline. However, the optimal thermal-hydraulic performance was found in the use of the concave delta winglet at 1.37 with a staggered vortex generators arrangement. The results of this study indicated that the use of perforated vortex generators could reduce the pressure drop with a slight decrease in the heat transfer rate.

Combined experimental and numerical studies on flow characteristic and heat transfer in ribbed channels with vortex generators of various types and arrangements

This work numerically and experimentally studies the heat transfer performances and flow characteristics of vortex generators (VGs) in a high aspect ratio rectangular ribbed channel with the Reynolds number ranging from 20000 to 100000. The steady liquid crystal thermography (LCT) method is adopted to link the images captured by experiments and the Nusselt numbers. Four different cases combining ribs and VGs are considered, and they are compared with a case with five continuous ribs in the channel. For the first time, the effect of winglet VGs and the tetrahedral VGs on heat transfer performance are compared. Simultaneously, two different arrangements of VGs, i.e. common-flow-down VGs and common-flow-up VGs are also studied to figure out which arrangement is better for improving the heat transfer performance. Simulations are conducted to systematically compare the fluid flow and local heat transfer characteristics to reveal the underlying thermo-fluid mechanisms of the considered cases by using three-dimensional CFD numerical simulations with a verified turbulence model, i.e., the SST k-ω model in the transition state. Results indicate that in the range of 0 < x/P < 1, the Nusselt number is enhanced to a large extent due to larger space for the flow reattachment. In addition, it is found that the winglet VGs perform better than the tetrahedral VGs. The winglet VGs with the common-flow-down arrangement give the best overall thermal performance at all Reynolds numbers in most cases. More specifically, the heat transfer performance can be improved up to 5.51% by adopting the common-flow-down VGs compared with the case having five continuous ribs. Furthermore, the flow characteristics reveal that longitudinal VGs can generate vortices to disturb the boundary layers, which can enhance the flow mixing and augment the heat transfer performance.

The optimal longitudinal location of curved winglets for better thermal performance of a finned-tube heat exchanger

The influence of longitudinal location of curved delta winglet vortex generator on the heat transfer of a finned-tube heat exchanger is numerically studied. The vertical right-angled side of the winglet vortex generator is arranged facing the main flow direction. Longitudinal vortex intensity and heat transfer are obviously affected by the longitudinal location of the vortex generator. There is an optimal longitudinal location of vortex generator for the largest heat transfer performance. At the optimal location, Nusselt number increases by 15.2%–43.9% and 5.4%–9.8%, while friction factor only increases by 12.2%–15.7% and 4.8%–12.2% compared with the plain fin and the original location, respectively. Thermal performance factor of the optimal longitudinal location increases by 8.1% compared with the original location and reaches up to 1.38. The pressure loss of the curved vortex generator is obviously smaller than that of the corresponding straight vortex generator. Good corresponding relationship exists between the Nusselt number and the intensity of longitudinal vortices, which means the intensity of the secondary flow determines the heat transfer. The results are of significance for the design and optimization of the studied finned-tube heat exchanger with curved delta winglet vortex generators.

Thermal-Hydraulic Performance Analysis by Means of Rectangular Winglet Vortex Generators in a Channel: An Experimental Study

Vortex generators (VGs) are one of the effective passive models used to increase the heat transfer rate in heat exchangers. In this experiment, heat transfer from six cylinders heated to the airflow was improved by attaching rectangular winglet vortex generators (RWVGs) to a plate in a rectangular channel. The installation aimed to increase the value of the thermal-hydraulic performance evaluation criteria in the line. This experimental study was carried out by varying the fluid flow velocity from 0.4 m/s to 2 m/s with an interval of 0.2 m/s in the channel. Three pairs of VGs were arranged in both in-line and staggered configurations. The experimental results show that the thermal-hydraulic performance evaluation criteria for three pairs of vortex generators in the staggered configuration was 15.17% higher than the baseline, while the thermal-hydraulic performance of the in-line arrangement was 1.54% higher than the staggered one.

Thermal-Hydraulic Performance Analysis by Means of Rectangular Winglet Vortex Generators in a Channel: An Experimental Study

Vortex generators (VGs) are one of the effective passive models used to increase the heat transfer rate in heat exchangers. In this experiment, heat transfer from six cylinders heated to the airflow was improved by attaching rectangular winglet vortex generators (RWVGs) to a plate in a rectangular channel. The installation aimed to increase the value of the thermal-hydraulic performance evaluation criteria in the line. This experimental study was carried out by varying the fluid flow velocity from 0.4 m/s to 2 m/s with an interval of 0.2 m/s in the channel. Three pairs of VGs were arranged in both in-line and staggered configurations. The experimental results show that the thermal-hydraulic performance evaluation criteria for three pairs of vortex generators in the staggered configuration was 15.17% higher than the baseline, while the thermal-hydraulic performance of the in-line arrangement was 1.54% higher than the staggered one.

Large eddy simulation of an inclined jet in crossflow with vortex generators

ABSTRACT Film cooling is one of the essential approaches to cool high-performance turbine blades. Film cooling with delta winglet vortex generator pair (DWVGP) placed upstream of the cooling hole is investigated by large eddy simulation (LES) at the blowing ratio of M=1.0. Film cooling effectiveness and vortical structures are evaluated in the flow field of a jet in crossflow (JICF). Results indicate that film cooling effectiveness increases significantly for the DWVGP case. As a dominant vortex structure, the ubiquitous counter-rotating vortex pair (CRVP) is recognized in the flow field. It has a detrimental effect that lifts the coolant off the cooling surface. The DWVGP evolved anticounter-rotating vortex pair (anti-CRVP) has the opposite sense of rotation to the jet introduced CRVP, which undertakes vorticity decay when developing downstream of the cooling hole. With the downwash effect of anti-CRVP, the reattachment of coolant is earlier, and a wide region of enhanced film cooling effectiveness in the spanwise direction is achieved. The coherent vortex structures including the classical vortices in the flow field and the vortex generator pair introduced vortices are analyzed. The genesis and evolution mechanism of CRVP with and without the vortex generators are discussed. It indicates that three branches of upstream spiral structures from the nozzle tube contribute to the CRVP. The merging of CRVP upstream branches is delayed by the vortex generators evolved anti-CRVP, which postpones the formation of downstream CRVP.

Review on Heat Transfer Enhancement by Louvered Fin

The heat transfer enhancement is recycled in many engineering uses such as heat exchangers, refrigeration and air conditioning structures, chemical apparatuses, and automobile radiators. Hence many enhancing extended fin patterns are developed and used. In multi louvered fin, in this segment for multi-row fin and tube heat exchanger, an increase in heat transfer enhancement is found 58% for ReH = 350. When the Reynolds number is 1075, the temperature gradient is more distinct for greater louver angle that is the higher heat transfer enhanced for large louver angle. For variable louver angle heat exchanger, the maximum heat transfer improvement achieved by 118% Reynolds number at 1075. In the vortex generator for the delta winglet vortex generator, the extreme enhancement of heat transfer increased to 16% compared to the baseline geometry (at ReDh = 600). For a compact louvered heat exchanger, the results showed that a regular arrangement of louvered fins gives a 9.3% heat transfer improvement. In multi-region louver fins and flat tubes heat exchanger, the louver fin with 4 regions and the louver fin with 6 regions are far better than the conventional fin in overall performance. At the same time, the louver fin with 6 regions is also better than the louver fin with 4-region. The available work is in experimental form as well as numerical form performed by computational fluid dynamics.

An experimental study of heat transfer enhancement with winglets inside a tube

The thermal enhancement and pressure drop in a circular tube with radially-arrayed winglet vortex generator (VG) mounted inside at different orientations were experimentally studied. A series of four winglet rings containing VGs were on the inner surface of the tube at different sections. The effects of winglet attack angles β (0–45°), pitch ratios PR (1.6–4.8), porosity ratio γ (0–20%), winglet length L (10–20 mm), and inclination angle α (0–30°) on heat transfer and pressure drop characteristics were carefully examined. The study was carried out at Reynolds numbers (Re) ranging from 6 × 103 to 2.7 × 104 nestling in the turbulent flow regime. Results showed a significant effect of the winglets on the heat transfer enhancement and pressure penalty compared to the smooth tube. Experiments further revealed that as the length or attack angle of winglets increased, both Nusselt number (Nu) and friction factor (f) were intensified. When it turned to pitch ratio and inclination angle of winglets, the trend became adverse. By comparing the contribution of different winglet parameters, it is preferable to optimize the pitch ratio (PR) other than length, inclination angle (α) nor attack angle (β) for a higher thermal enhancement. The case of small porosity ratio (γ = 10%) at a low Re yields the maximum thermal enhancement of 1.26. Empirical correlations for Nu and f were generated for the winglets based on experimental data.

Development of hybrid thermal management techniques for battery packs

In this study, the thermal management issue of electric vehicle and hybrid electric vehicle battery pack is studied. Passive and hybrid techniques are developed and used in the battery pack. Multiple delta winglet vortex generators are introduced to enhance turbulence before the air flow interacts with the cells’ surface. Multiple jet inlets are introduced that enable the air flow to change its directions and pass through the dead air regions. A hybrid technique is also used in which a liquid jacket is added to each of the cells. The liquid within the jackets is in contact with the cells maximizing the contact surface area to improve heat transfer. Steady state computational fluid dynamic simulations are performed to study the effects of the passive and hybrid techniques added to the battery pack. The results indicate a substantial improvement in the temperature uniformity. The temperature difference of the hybrid battery pack reduces from 4.87 °C to 1.26 °C. Additionally, the temperature variance at the cell level reduces from 3.29 °C to 0.36 °C. This battery pack does not require moving parts and pumping power and it can achieve high levels of temperature uniformity.

Efek vortex generators terhadap peningkatan perpindahan panas pada aliran melewati heated tubes

In this decade, improving the rate of heat transfer has become a big challenge. The high thermal resistance of the gas side of the heat exchanger has an impact on the low rate of heat transfer. Therefore, an experimental study was carried out aimed at looking at conditions of hot temperature and decreased air flow pressure through a heated tube in a rectangular channel using artificial surfaces, namely the concave delta winglet and delta winglet vortex generators. Concave delta winglet vortex generators (CDW VGs) are installed in-line and staggered with one, and two pairs are arranged in common-flow-down (CFD) in the direction of flow with an angle of attack of 15o. The experimental results show that the best thermal performance is observed in the use of two rows CDW VGs staggered, where the value of performance evaluation criteria (PEC) is 28.88% higher than the use of CDW VGs in-line, DW VGs staggered and DW VGs in-line at the same Reynolds number. At the same Reynolds number, the Nusselt number ratio and the friction factor ratio increased 45.25% and 152.05% respectively, occurring in two rows of CDW VGs staggered compared to other vortex generators.Keywords: vortex generators, heat transfer, Nusselt number, friction factor, PEC

Experimental analysis and exergetic assessment of the solar air collector with delta winglet vortex generators and baffles

To increase the efficiency of solar air collectors (SACs), the combined effects of baffles and delta winglet vortex generator (DWLVG) on the performance of SAC have been investigated. An experimental setup has been made, and numerical simulation is carried out in Ansys Fluent. The numerical investigation is validated by the experimental study and focused on the number of baffles as well as the number and the height of DWLVG. The results show that the SAC with no baffles and DWLVG has the lowest efficiency with the maximum value of 13%, while for SAC with six baffles and three pairs of DWLVG, the efficiency reaches up to 20%. The exergy analysis of three cases, SAC without baffles and DWLVG, SAC with six baffles without DWLVG, and SAC with six baffles and three pairs of DWLVG, shows that the maximum exergy efficiency of the SAC is 30.44% and occurs when the height ratio and the number of DWLVG pairs are 0.5 and 3. The results show that for SAC with six baffles and three pairs of DWLVG, the energy and exergy efficiency improve 7.4% and 12% on an average basis compared to the typical flat plate SAC, respectively. This improvement in thermal and exergy efficiency is due to the implementation of DWLVG which produces more turbulence and eliminates the vortices generated at the corners of SAC.

Heat Transfer Enhancement of Plate-Fin Heat Sinks with Different Types of Winglet Vortex Generators

Because the delta winglet in common-flow-down configuration has been recognized as an excellent type of vortex generators (VGs), this study aims to experimentally and numerically investigate the thermo-hydraulic performance of four different forms of winglet VGs featuring sweptback delta winglets in the channel flow in the range 200 &lt; Re &lt; 1000. Both Nusselt number and friction factor of plate-fin heat sinks having different forms of winglets, including delta winglet pair (DWP), rectangular winglet pair (RWP), swept delta winglet pair (SDWP), and swept trapezoid winglet pair (STWP), were measured in a standard wind tunnel without bypass in this study. Four rows of winglets with in-line arrangement were punched on each 10-mm-long, 0.2-mm-thick copper plate, and a total of 16 pieces of copper plates with spacing of 2 mm were fastened together to achieve the heat sink. The projected area, longitudinal and winglet tip spacing, height and angle of attack of those winglets were fixed. Besides that, three-dimensional numerical simulation was also performed in order to investigate the temperature and fluid flow over the plate-fin. The results showed that the longitudinal, common-flow-down vortices generated by the VGs augmented the heat transfer and pressure drop of the heat sink. At airflow velocity of 5 m/s, the heat transfer coefficient and pressure drop of plain plate-fin heat sink were 50.8 W/m2·K and 18 Pa, respectively, while the heat transfer coefficient and the pressure drop of heat sink having SDWP were 70.4 W/m2·K and 36 Pa, respectively. It was found that SDWP produced the highest thermal enhancement factor (TEF) of 1.28 at Re = 1000, followed by both RWP and STWP of similar TEF in the range 200 &lt; Re &lt; 1000. The TEF of DWP was the lowest and it was rapidly increased with the increase of airflow velocity.

Performa Termal dan Hidrolik Aliran Udara Melalui Vortex Generator Berlubang Tipe Concave Rectangular Winglet di dalam Saluran Persegiempat: Studi Eksperimen

Fin and tube heat exchangers use gas as a cooling/heating medium on the fin side. The low thermal conductivity of gases results in high thermal resistance, which results in a low rate of heat transfer. Therefore, the researchers sought to reduce thermal resistance on the fin side. This study aims to increase heat transfer by reducing thermal resistance using a longitudinal vortex generator. However, the use of vortex generators will increase the pressure drop. Perforated vortex generators were investigated in this study to overcome this problem. Concave rectangular winglet vortex generator at an angle of attack of 30° with variations of without hole, one, two, and three holes were studied. In this experiment, the number of pairs of vortex generators was varied from one to three pairs. A plate on which the vortex generator is mounted is heated at a heat rate of 35 W. Air enters the channel through the straightener at variations in the velocity of 0.4 m/s to 2 m/s at intervals of 0.2 m/s. The results showed that the value of the convection heat transfer coefficient for the use of perforated concave rectangular winglet vortex generators was 85.4% higher than the baseline. This value is 13.7% higher than the use of perforated rectangular winglet vortex generators. Whereas the value of pressure drop for the use of perforated concave rectangular winglet vortex generators is five times higher than that of the baseline. This value is 104.9% higher than the use of perforated rectangular winglet vortex generators.