The Experts below are selected from a list of 303 Experts worldwide ranked by ideXlab platform
Yuwen Zhang - One of the best experts on this subject based on the ideXlab platform.
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numerical simulation on flow and heat transfer of fin and tube heat exchanger with longitudinal vortex generators
International Journal of Thermal Sciences, 2015Co-Authors: Li Li, Lijun Yang, Xiaoze Du, Yuwen Zhang, Yongping YangAbstract:Abstract Fin-and-tube heat exchangers with plain fins are widely used in direct air-cooled condenser system in the power plant, because of its relatively simple property compared to some other fins with variable cross-sectional area channel. In the present study, heat transfer performance and pressure drop for fin-and-tube heat exchanger with longitudinal vortex generators (LVGs) on the fin surface were numerically investigated. Rectangular and delta Winglet pairs were punched/mounted on the fin surfaces to enhance the heat transfer of the air-side of the fin-and-tube heat exchangers. The results showed that the Nusselt numbers increased up to 20% for LVGs on plain fins comparing with plain fins channel without LVGs. The heat transfer enhancement by rectangular Winglets was more significant than that of the delta Winglets. The rectangular Winglet with angle of attack of 25°showed the best overall performance than any other angles of attack in rectangular Winglets configurations. Additionally, the delta Winglet with angle of attack of 45° showed the best overall performance than the other angles of attack in delta Winglets configurations.
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numerical study of heat transfer enhancement by punched Winglet type vortex generator arrays in fin and tube heat exchangers
International Journal of Heat and Mass Transfer, 2012Co-Authors: Y L He, Yuwen ZhangAbstract:Abstract The potential of punched Winglet type vortex generator (VG) arrays used to enhance air-side heat-transfer performance of finned tube heat exchanger is numerically investigated. The arrays are composed of two delta-Winglet pairs with two layout modes of continuous and discontinuous Winglets. The heat transfer performance of two array arrangements are compared to a conventional large Winglet configuration for the Reynolds number ranging from 600 to 2600 based on the tube collar diameter, with the corresponding frontal air velocity ranging from 0.54 to 2.3 m/s. The effects of different geometry parameters that include attack angle of delta Winglets (β = 10 deg, β = 20 deg, β = 30 deg) and the layout locations are examined. The numerical results show that for the punched VG cases, the effectiveness of the main vortex to the heat transfer enhancement is not fully dominant while the “corner vortex” also shows significant effect on the heat transfer performance. Both heat transfer coefficient and pressure drop increase with the increase of attack angle β for the side arrangements; the arrays with discontinuous Winglets show the best heat transfer enhancement, and a significant augmentation of up to 33.8–70.6% in heat transfer coefficient is achieved accompanied by a pressure drop penalty of 43.4–97.2% for the 30 deg case compared to the plain fin. For the front arrangements of VGs higher heat transfer enhancement and pressure drop penalty can be obtained compared to that of the side arrangement cases; the case with front continuous Winglet arrays has the maximum value of j/f, a corresponding heat transfer improvement of 36.7–81.2% and a pressure drop penalty of 60.7–135.6%.
Fangpan Zhong - One of the best experts on this subject based on the ideXlab platform.
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A Novel Suction-Side Winglet Design Philosophy for High-Pressure Turbine Rotor Tips
Journal of Turbomachinery, 2017Co-Authors: Chao Zhou, Fangpan ZhongAbstract:Winglet tips are promising candidates for future high-pressure turbine rotors. Many studies found that the design of the suction-side Winglet is the key to the aerodynamic performance of a Winglet tip, but there is no general agreement on the exact design philosophy. In this paper, a novel suction-side Winglet design philosophy in a turbine cascade is introduced. The Winglets are obtained based on the near-tip flow field of the datum tip geometry. The suction-side Winglet aims to reduce the tip leakage flow particularly in the front part of the blade passage. It is found that on the casing endwall, the pressure increases in the area where the Winglet is used. This reduces the tip leakage flow in the front part of the blade passage and the pitchwise pressure gradient on the endwall. As a result, the size of the tip leakage vortex reduces. A surprising observation is that the novel optimized Winglet tip design eliminates the passage vortex and results in a further increasing of the efficiency. The tip leakage loss of the novel Winglet tip is 18.1% lower than the datum cavity tip, with an increase of tip surface area by only 19.3%. The spanwise deflection of the Winglet due to the centrifugal force is small. The tip heat load of the Winglet tip is 17.5% higher than that of the cavity tip. Numerical simulation shows that in a turbine stage, this Winglet tip increases the turbine stage efficiency by 0.9% mainly by eliminating the loss caused by the passage vortex at a tip gap size of 1.4% chord compared with a cavity tip.
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A Novel Suction Side Winglet Design Method for High Pressure Turbine Rotor Tips
Volume 2B: Turbomachinery, 2016Co-Authors: Chao Zhou, Fangpan ZhongAbstract:Winglet tips are promising candidates for future high pressure turbine rotors. Many studies found that the design of the suction side Winglet is the key to the aerodynamic performance of a Winglet tip, but there is no general agreement on the exact design method. In this paper, a novel suction side Winglet design method will be introduced. The Winglets are obtained based on the near tip flow field of the datum tip geometry. The suction side Winglet aims to reduce the tip leakage flow particularly in the front part of the blade passage. It is found that on the casing endwall, the pressure increases in the area where the Winglet is used. This reduces the tip leakage flow in the front part of the blade passage and the pitchwise pressure gradient on the endwall. As a result, the size of the tip leakage vortex reduces. A surprising observation is that the novel Winglet tip design eliminates the scraping vortex and results in a further increasing of the efficiency. The tip leakage loss of the novel Winglet tip is 23% lower than the datum cavity tip, with an increase of tip surface area by only 20%. The spanwise deflection of the Winglet due to the centrifugal force is small. Numerical simulation shows that in a turbine stage, this Winglet tip increases the turbine stage efficiency by 0.9% at a tip gap size of 1% span compared with a cavity tip.
Gautam Biswas - One of the best experts on this subject based on the ideXlab platform.
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a note on the flow and heat transfer enhancement in a channel with built in Winglet pair
International Journal of Heat and Fluid Flow, 2007Co-Authors: S R Hiravennavar, E G Tulapurkara, Gautam BiswasAbstract:Abstract Counter rotating longitudinal vortices produced by Winglet in a channel are known to enhance heat transfer. In the present investigation the flow structure and heat-transfer enhancement by a Winglet pair of non-zero thickness has been studied. A delta Winglet pair type vortex generator is placed in a hydrodynamically developed and thermally developing laminar channel flow. Computations are done by solving the unsteady, three-dimensional, incompressible Navier–Strokes equations and energy equation using a modified Marker-and-Cell (MAC) method. The flow structure is complex and consists of main, corner and induced vortices. It is observed that as compared to a channel without Winglets, the heat transfer is enhanced by 33% when single Winglet is used and by 67% when a Winglet pair is employed. Effects of thickness of the Winglets and Reynolds number on the heat transfer augmentation are presented.
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Winglet-type vortex generators for plate-fin heat exchangers using triangular fins
Numerical Heat Transfer Part A-applications, 2000Co-Authors: R. Vasudevan, Vinayak Eswaran, Gautam BiswasAbstract:Vortex generators in the form of delta Winglet pairs have already been proposed by many researchers for enhancement of the heat transfer rate in plate-fin heat exchangers. In this work, the enhancement potential of triangular fins (which are widely used inserts between the plates of the plate-fin heat exchanger) having delta Winglets mounted on their slant surfaces has been computed. The performance of this combination is evaluated for varying angles of attack of the Winglet and different thermal boundary conditions. The performance of the combination of triangular fins and Winglets with stamping on the slant surfaces also has been evaluated.
Hussein A. Mohammed - One of the best experts on this subject based on the ideXlab platform.
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Heat transfer enhancement and pressure drop for fin-and-tube compact heat exchangers with wavy rectangular Winglet-type vortex generators
International Communications in Heat and Mass Transfer, 2014Co-Authors: Ahmadali Gholami, Mazlan Abdul Wahid, Hussein A. MohammedAbstract:Abstract In the current work, heat transfer enhancement and pressure loss penalty for fin-and-tube compact heat exchangers with the wavy-up and wavy-down rectangular Winglets as special forms of Winglet are numerically investigated in a relatively low Reynolds number flow. The rectangular Winglets were used with a particular wavy form for the purpose of enhancement of air side heat transfer performance of fin-and-tube compact heat exchangers. The effect of Reynolds numbers from 400 to 800 and angle of attack of 30° of wavy rectangular Winglets are also examined. The effects of using the wavy rectangular Winglet, conventional rectangular Winglet configuration and without Winglet as baseline configuration, on the heat transfer characteristics and flow structure are studied and analyzed in detail for the inline tube arrangements. The results showed that the wavy rectangular Winglet can significantly improve the heat transfer performance of the fin-and-tube compact heat exchangers with a moderate pressure loss penalty. In addition, the numerical results have shown that the wavy Winglet cases have significant effect on the heat transfer performance and also, this augmentation is more important for the case of the wavy-up rectangular Winglet configuration.
R S Agarwal - One of the best experts on this subject based on the ideXlab platform.
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experimental study of the effect of Winglet location on heat transfer enhancement and pressure drop in fin tube heat exchangers
Applied Thermal Engineering, 2005Co-Authors: S M Pesteei, P M V Subbarao, R S AgarwalAbstract:Abstract Local heat transfer coefficients were measured on fin-tube heat exchanger with Winglets using a single heater of 2 inch diameter and five different positions of Winglet type vortex generators. The measurements were made at Reynolds number about 2250. Flow losses were determined by measuring the static pressure drop in the system. Results showed a substantial increase in the heat transfer with Winglet type vortex generators. It has been observed that average Nusselt number increases by about 46% while the local heat transfer coefficient improves by several times as compared to plain fin-tube heat exchanger. The maximum improvement is observed in the re-circulation zone. The best location of the Winglets was with Δ X = 0.5 D and Δ Y = 0.5 D . The increase in pressure drop for the existing situation was of the order of 18%.
