The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Qiuwang Wang - One of the best experts on this subject based on the ideXlab platform.
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an investigation of the thermo hydraulic performance of the smooth wavy fin and elliptical tube heat exchangers utilizing new type vortex generators
Applied Energy, 2016Co-Authors: Babak Lotfi, Bengt Sunden, Qiuwang WangAbstract:A three-dimensional CFD numerical simulation is successfully carried out on thermo-hydraulic characteristics of a new smooth wavy fin-and-elliptical tube (SWFET) heat exchanger with three new types of vortex generators (VGs), namely – rectangular trapezoidal winglet (RTW), Angle rectangular winglet (ARW) and curved Angle rectangular winglet (CARW). Several parameters have been examined in this study. There have a pronounced effect on the thermo-hydraulic performance. In addition the results are analyzed from the viewpoint of the field synergy principle which emphasizes that the reduction of the synergy Angle between velocity and fluid temperature gradient is the principal mechanism for enhancement of heat transfer performance. These parameters include: Reynolds number (based on the hydraulic diameter, ReDh=500–3000), geometric shape of VGs, Attack Angle of VGs (αVG=15–75°), placement of VG pairs (up- or/and downstream), tube ellipticity ratio (e=0.65–1.0) and wavy fin height (H=0.8–1.6mm). The results demonstrate that with increasing Reynolds number and wavy fin height, decreasing the tube ellipticity ratio, the heat transfer performance of the SWFET heat exchanger is enhanced. The SWFET heat exchanger with the advantages of using CARW VGs and RTW VGs at smaller and larger Attack Angles, respectively, presents good thermo-hydraulic performance enhancement. Finally, new correlations are proposed to estimate the values of the average Nusselt number Nu, friction factor f and synergy Angle θ based on the Reynolds number, Attack Angle of VGs, tube ellipticity ratio and wavy fin height.
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3d numerical investigation of flow and heat transfer characteristics in smooth wavy fin and elliptical tube heat exchangers using new type vortex generators
Energy, 2014Co-Authors: Babak Lotfi, Min Zeng, Bengt Sunden, Qiuwang WangAbstract:3D computational analysis was performed to investigate heat transfer and pressure drop characteristics of flow in SWFET (Smooth Wavy Fin-and-Elliptical Tube) heat exchanger with four new VGs (vortex generators), RTW (rectangular trapezoidal winglet), ARW (Angle rectangular winglet), CARW (curved Angle rectangular winglet) and WW (Wheeler wishbone). The numerical model was well validated with the available experimental results. Numerical results illustrate that vortex generators can bring about further heat transfer enhancement through careful adjustment of the position with respect to the elliptical tube, type and Attack Angle of vortex generators. The influences of the geometrical factors including Attack Angles of the winglets (alpha(vG) = 15 degrees,30 degrees,45 degrees,60 degrees and 75 degrees) and width/length aspect ratio (w/l = 0.5,1.0) of the Wheeler wishbones on enhancing the heat transfer performance of a smooth wavy fin heat exchanger with a three-row staggered elliptical tube bundle are investigated. A parametric study on the winglet vortex generators indicated that for the small Attack Angle, CARW vortex generators gives better thermohydraulic performance under the present conditions. The best thermal performance with winglet VGs in larger Attack Angle, was obtained at RTW VGs arrangement. For the SWFET heat exchangers, the WW VGs with w/l = 0.5 provide the best heat transfer performance. (C) 2014 Elsevier Ltd. All rights reserved. (Less)
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3d numerical investigation of flow and heat transfer characteristics in smooth wavy fin and elliptical tube heat exchangers using new type vortex generators
Energy, 2014Co-Authors: Babak Lotfi, Min Zeng, Bengt Sunden, Qiuwang WangAbstract:3D computational analysis was performed to investigate heat transfer and pressure drop characteristics of flow in SWFET (Smooth Wavy Fin-and-Elliptical Tube) heat exchanger with four new VGs (vortex generators), RTW (rectangular trapezoidal winglet), ARW (Angle rectangular winglet), CARW (curved Angle rectangular winglet) and WW (Wheeler wishbone). The numerical model was well validated with the available experimental results. Numerical results illustrate that vortex generators can bring about further heat transfer enhancement through careful adjustment of the position with respect to the elliptical tube, type and Attack Angle of vortex generators. The influences of the geometrical factors including Attack Angles of the winglets (αVG = 15∘,30∘,45∘,60∘ and 75°) and width/length aspect ratio (w/l = 0.5,1.0) of the Wheeler wishbones on enhancing the heat transfer performance of a smooth wavy fin heat exchanger with a three-row staggered elliptical tube bundle are investigated. A parametric study on the winglet vortex generators indicated that for the small Attack Angle, CARW vortex generators gives better thermohydraulic performance under the present conditions. The best thermal performance with winglet VGs in larger Attack Angle, was obtained at RTW VGs arrangement. For the SWFET heat exchangers, the WW VGs with w/l = 0.5 provide the best heat transfer performance.
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optimization of heat exchangers with vortex generator fin by taguchi method
Applied Thermal Engineering, 2010Co-Authors: Min Zeng, L H Tang, Qiuwang WangAbstract:A comparative study of effects of Attack Angle, length of vortex generator, height of vortex generator, fin material, fin thickness, fin pitch and tube pitch on fin performance of vortex-generator fin-and-tube heat exchanger is conducted by numerical method. The parameters of vortex-generator fin-and-tube heat exchangers are optimized by the Taguchi method. Eighteen kinds of models are made by compounding levels on each factor, and the heat transfer and flow characteristics of each model are analyzed. The results show that these six factors (fin pitch, longitudinal tube pitch, transverse tube pitch, length of vortex generator, height of vortex generator, and Attack Angle of vortex generator) have great influences on the JF-factor. The fin material and fin thickness have trifling effects on the JF-factor. The two optimal conditions (A1B3C3D2E1F2G1H3 and A2B2C2D3E1F2G1H3) are acquired, and the reproducibility of the results is verified by two analytical results.
Yuwen Zhang - One of the best experts on this subject based on the ideXlab platform.
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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%.
Jiangbo Wu - One of the best experts on this subject based on the ideXlab platform.
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effect of longitudinal vortex generator on heat transfer in rectangular channels
Applied Thermal Engineering, 2012Co-Authors: Jiangbo WuAbstract:Abstract Average convective heat transfer on the top and bottom surfaces of a plain plate and four plates with a pair of delta winglet longitudinal vortex generator punched directly from the plates at Attack Angles of 15°, 30°, 45° and 60° respectively, is experimentally and numerically studied in the present paper. The plate fixed horizontally in the center of the tested channel is designed to simulate the forced heat transfer on the both surfaces of a single piece of fin in a fin-tube heat exchanger. Experimental results show that the average Nusselt number on the surfaces of plate increases with the increase of the Attack Angle of delta winglet pair compared with that of plain plate without delta winglet pair in the test range. The average Nusselt number of the plate with Attack Angle of 60° is slightly higher than that of plate with Attack Angle of 45°, yet may bring larger pressure drop. Strong longitudinal vortices are visualized when air flow across the leading-edges of the winglet pair. And a portion of air stream flows into the lower channel through the punched holes on the plates after rushing at the frontal face of delta winglet, and disturbs the flow field of the lower channel further. The heat transfer in the tested channel of five cases is also numerically investigated. Variance of average Nusselt number between the numerical results and experimental results for the five cases are all less than 10%, validating the present models and methods used for the simulation of fin channel flow with punched vortex generators feasible and reliable. The computed velocity and temperature fields are analyzed to understand the details of fin channel flow with longitudinal vortex generator. The experimental and numerical results reveal that the transverse flow of air stream through the punched holes disturbs the air flow in the lower channel, enhancing the heat transfer on the under surface of fin.
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investigation on laminar convection heat transfer in fin and tube heat exchanger in aligned arrangement with longitudinal vortex generator from the viewpoint of field synergy principle
Applied Thermal Engineering, 2007Co-Authors: Jiangbo WuAbstract:3-D numerical simulation results are presented for laminar flow heat transfer of the fin-and-tube surface with vortex generators. The effects of Reynolds number (from 800 to 2000), the Attack Angle (30° and 45°) of delta winglet vortex generator are examined. The numerical results are analyzed from the viewpoint of field synergy principle. It is found that the inherent mechanism of heat transfer enhancement by longitudinal vortex can be explained by the field synergy principle, the second flow generated by the vortex generators results in the reduction of the intersection Angle between the velocity and fluid temperature gradient. In addition, the heat transfer enhancement of delta winglet with the Attack Angle of 45° is larger than that of 30°, while the delta winglet with the Attack Angle of 45° results in an increase of the pressure drop, however, the delta winglet with the Attack Angle of 30° results in a slight decrease.
Babak Lotfi - One of the best experts on this subject based on the ideXlab platform.
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an investigation of the thermo hydraulic performance of the smooth wavy fin and elliptical tube heat exchangers utilizing new type vortex generators
Applied Energy, 2016Co-Authors: Babak Lotfi, Bengt Sunden, Qiuwang WangAbstract:A three-dimensional CFD numerical simulation is successfully carried out on thermo-hydraulic characteristics of a new smooth wavy fin-and-elliptical tube (SWFET) heat exchanger with three new types of vortex generators (VGs), namely – rectangular trapezoidal winglet (RTW), Angle rectangular winglet (ARW) and curved Angle rectangular winglet (CARW). Several parameters have been examined in this study. There have a pronounced effect on the thermo-hydraulic performance. In addition the results are analyzed from the viewpoint of the field synergy principle which emphasizes that the reduction of the synergy Angle between velocity and fluid temperature gradient is the principal mechanism for enhancement of heat transfer performance. These parameters include: Reynolds number (based on the hydraulic diameter, ReDh=500–3000), geometric shape of VGs, Attack Angle of VGs (αVG=15–75°), placement of VG pairs (up- or/and downstream), tube ellipticity ratio (e=0.65–1.0) and wavy fin height (H=0.8–1.6mm). The results demonstrate that with increasing Reynolds number and wavy fin height, decreasing the tube ellipticity ratio, the heat transfer performance of the SWFET heat exchanger is enhanced. The SWFET heat exchanger with the advantages of using CARW VGs and RTW VGs at smaller and larger Attack Angles, respectively, presents good thermo-hydraulic performance enhancement. Finally, new correlations are proposed to estimate the values of the average Nusselt number Nu, friction factor f and synergy Angle θ based on the Reynolds number, Attack Angle of VGs, tube ellipticity ratio and wavy fin height.
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3d numerical investigation of flow and heat transfer characteristics in smooth wavy fin and elliptical tube heat exchangers using new type vortex generators
Energy, 2014Co-Authors: Babak Lotfi, Min Zeng, Bengt Sunden, Qiuwang WangAbstract:3D computational analysis was performed to investigate heat transfer and pressure drop characteristics of flow in SWFET (Smooth Wavy Fin-and-Elliptical Tube) heat exchanger with four new VGs (vortex generators), RTW (rectangular trapezoidal winglet), ARW (Angle rectangular winglet), CARW (curved Angle rectangular winglet) and WW (Wheeler wishbone). The numerical model was well validated with the available experimental results. Numerical results illustrate that vortex generators can bring about further heat transfer enhancement through careful adjustment of the position with respect to the elliptical tube, type and Attack Angle of vortex generators. The influences of the geometrical factors including Attack Angles of the winglets (αVG = 15∘,30∘,45∘,60∘ and 75°) and width/length aspect ratio (w/l = 0.5,1.0) of the Wheeler wishbones on enhancing the heat transfer performance of a smooth wavy fin heat exchanger with a three-row staggered elliptical tube bundle are investigated. A parametric study on the winglet vortex generators indicated that for the small Attack Angle, CARW vortex generators gives better thermohydraulic performance under the present conditions. The best thermal performance with winglet VGs in larger Attack Angle, was obtained at RTW VGs arrangement. For the SWFET heat exchangers, the WW VGs with w/l = 0.5 provide the best heat transfer performance.
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3d numerical investigation of flow and heat transfer characteristics in smooth wavy fin and elliptical tube heat exchangers using new type vortex generators
Energy, 2014Co-Authors: Babak Lotfi, Min Zeng, Bengt Sunden, Qiuwang WangAbstract:3D computational analysis was performed to investigate heat transfer and pressure drop characteristics of flow in SWFET (Smooth Wavy Fin-and-Elliptical Tube) heat exchanger with four new VGs (vortex generators), RTW (rectangular trapezoidal winglet), ARW (Angle rectangular winglet), CARW (curved Angle rectangular winglet) and WW (Wheeler wishbone). The numerical model was well validated with the available experimental results. Numerical results illustrate that vortex generators can bring about further heat transfer enhancement through careful adjustment of the position with respect to the elliptical tube, type and Attack Angle of vortex generators. The influences of the geometrical factors including Attack Angles of the winglets (alpha(vG) = 15 degrees,30 degrees,45 degrees,60 degrees and 75 degrees) and width/length aspect ratio (w/l = 0.5,1.0) of the Wheeler wishbones on enhancing the heat transfer performance of a smooth wavy fin heat exchanger with a three-row staggered elliptical tube bundle are investigated. A parametric study on the winglet vortex generators indicated that for the small Attack Angle, CARW vortex generators gives better thermohydraulic performance under the present conditions. The best thermal performance with winglet VGs in larger Attack Angle, was obtained at RTW VGs arrangement. For the SWFET heat exchangers, the WW VGs with w/l = 0.5 provide the best heat transfer performance. (C) 2014 Elsevier Ltd. All rights reserved. (Less)
Zhengjiang Zhang - One of the best experts on this subject based on the ideXlab platform.
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thermal hydraulic performance and optimization of Attack Angle of delta winglets in plain and wavy finned tube heat exchangers
Applied Thermal Engineering, 2019Co-Authors: Tariq Amin Khan, Yusheng Lin, Hua Zhu, Zhengjiang ZhangAbstract:Abstract This work is related to numerical investigation and optimization of the Attack Angle of delta winglet type vortex generators in plain and wavy finned-tube heat exchangers. For this purpose, three-dimensional numerical simulation data and a multi-objective genetic algorithm with Artificial neural network are employed. The heat exchanger models considered in this study are three rows of tubes in staggered arrangement. The Angle of Attack (α) of delta winglets and Reynolds number varies from 15° to 75° and 500 to 1300, respectively. Results are illustrated by investigating the flow structures and local heat transfer coefficient. Results show that compared to plain fins, wavy fins enhance the heat transfer performance of the heat exchanger due to constant disruption of thermal boundary. Applying delta winglets on the plain and wavy fins further increased the heat transfer by energizing flow in the wake of tubes while friction factor is also increased. To achieve a maximum heat transfer enhancement and a minimum pressure drop, the optimal Angle of Attack for varying Reynolds numbers are calculated using the Pareto optimal strategy. For this purpose, CFD data, artificial neural network and a multi-objective genetic algorithm are combined. Results show that compared to the corresponding smooth fins, heat transfer per unit volume (Qv) and pumping power per unit volume (Pv) performances of delta winglets in wavy finned-tube heat exchanger has increased up to 12.5% and 7.41%, respectively. Similarly, for plain finned-tube heat exchangers, the maximum increase in Qv is 14.7% while Pv is increased by 6.93%.