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Analysis of Turbulent Heat Transfer and Fluid Flow in Channels with Various Ribbed Internal Surfaces

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Journal of Thermal Science 2011年第3期20卷 260-267页

作者： smith Eiamsa-ard Wayo Changcharoen Department of Mechanical Engineering Faculty of Engineering Mahanakorn University of Technology Bangkok 10530 Thailand

This paper presents results of a numerical investigation of heat transfer and flow pattern characteristics of a channel with repeated ribs on one broad wall. Numerical computations are performed for seven ribs placed on the bottom wall of a channel for Reynolds numbers ranging from 10,000 to 30,000. The newly modified ribs (the ones with convex pointing upstream/downstream rib, wedge pointing upstream/downstream rib, concave pointing upstream/downstream rib and also concave-concave rib as well as convex-concave rib), are proposed for simulation with prospect to reduce flow separation and extend reattachment area compared to the unmodified square rib. The numerical results are reported in forms of flow structure, temperature field, turbulent kinetic energy, Nusselt number, friction factor and thermal enhancement factor. The results indicate the rib with concave-concave surfaces efficiently suppresses flow separation bubble in the corner of the rib and induces large recirculation zone over those of the others, hence giving the highest Nusselt number and friction factor. On the other hand, the one with convex-concave surface provides the lowest friction factor with moderate Nusselt number. Due to the prominent effect of its low friction factor, the rib with convex-concave surface offers the highest thermal enhancement factor of 1.19.

关键词： Rib Turbulent flow Heat transfer Reattachment zone Flow separation

Turbulent heat transfer and pressure loss in a square channel with discrete broken V-rib turbulators

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Journal of Hydrodynamics 2016年第2期28卷 275-283页

作者： Promthaisong PITAK Eiamsa-ard PETPICES Jedsadaratanachai WITHADA Eiamsa-ard smith Faculty of Engineering Mahanakorn University of Technology Faculty of Industrial Technology Phetchaburi Rajabhat University Faculty of Engineering King Mongkut's Institute of Technology Ladkrabang

Turbulent periodic flow, heat transfer, friction loss and thermal enhancement characteristics in a three-dimensional horizo- ntal square channel with broken V-ribs （B-VR） are numerically investigated. The computations are based on the finite volume method, and the SIMPLE algorithm with QUICK scheme is implemented. The B-VR were installed on both sides of a plate which was diagonally placed in a square channel to produce longitudinal vortex flows through the tested section. Effects of different open comer ratios （ d/H = 0, 0.01, 0.02, 0.03, 0.04 and 0.05） on heat transfer and pressure loss in the channel and the results of the B-VR are studied. The pitch ratio （PR = p/H） and blockage ratio （BR = p/H） of B-VRs were fixed at 1.0 and 0.15, respectively. As compared with the channel without V-rib, the one with B-VRs possessed considerably higher heat transfer and friction loss. It is observed that apart from the rise of Reynolds number, the reduction of the open comer ratios leads to an increase in the Nusselt number and friction factor due to the weaker turbulence and lower resistance to the flow. According to the computational results for B-VRs, the optimum thermal enhancement is fotmd at d/H = 0.

关键词： channel periodic flow heat transfer friction loss broken V-ribs

Numerical prediction of vortex flow and thermal separation in a subsonic vortex tube

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2006年第8期7卷 1406-1415页

作者： smith Eiamsa-ard PONGJET Promvonge Department of Mechanical Engineering Faculty of Engineering Mahanakorn University of Technology Bangkok 10530 Thailand Department of Mechanical Engineering Faculty of Engineering King Mongkut's Institute of Technology Ladkrabang Bangkok 10520 Thailand

This work was aimed at gaining understanding of the physical behaviours of the flow and temperature separation process in a vortex tube. To investigate the cold mass fraction’s effect on the temperature separation, the numerical calculation was carried out using an algebraic Reynolds stress model (ASM) and the standard k-ε model. The modelling of turbulence of com-pressible, complex flows used in the simulation is discussed. Emphasis is given to the derivation of the ASM for 2D axisymmet-rical flows, particularly to the model constants in the algebraic Reynolds stress equations. The TEFESS code, based on a staggered Finite Volume approach with the standard k-ε model and first-order numerical schemes, was used to carry out all the computations. The predicted results for strongly swirling turbulent compressible flow in a vortex tube suggested that the use of the ASM leads to better agreement between the numerical results and experimental data, while the k-ε model cannot capture the stabilizing effect of the swirl.

关键词： Vortex tube Cold mass fraction Swirl fiow Temperature separation Flow field

插入双面有三角形翅片的金属带对热交换管中流动和传热特性的影响(英文)

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Chinese Journal of Chemical Engineering 2011年第3期19卷 410-423页

作者： smith Eiamsa-ard Pongjet Promvonge Department of Mechanical Engineering Faculty of Engineering Mahanakorn University of Technology Faculty of Engineering King Mongkut's Institute of Technology Ladkrabang

The convective heat transfer and friction behaviors of turbulent tube flow through a straight tape with double-sided delta wings(T-W)have been studied *** the current work,the T-W formed on the tape was used as vortex generators for enhancing the heat transfer coefficient by breakdown of thermal boundary layer and by mixing of fluid flow in *** T-W characteristics are(1)T-W with forward/backward-wing arrangement,(2)T-W with alternate axis(T-WA),(3)three wing-width ratios and(4)wing-pitch *** experimental result reveals that for using the T-W,the increases in the mean Nusselt number(Nu)and friction factor are,respectively,up to 165%and 14.8 times of the plain tube and the maximum thermal performance factor is *** is also obvious that the T-W with forward-wing gives higher heat transfer rate than one with backward-wing around 7%. The present investigation also shows that the heat transfer rate and friction factor obtained from the T-WA is higher than that from the *** addition,the flow pattern and temperature fields in the T-W tube with both backward and forward wings were also examined numerically.

关键词： fluid flow heat transfer tape with centre-wing wing alternate axis vortex

Heat Transfer Behavior in a Square Duct with Tandem Wire Coil Element Insert

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Chinese Journal of Chemical Engineering 2012年第5期20卷 863-869页

作者： smith Eiamsa-ard Narin Koolnapadol Pongjet Promvonge Department of Mechanical Engineering Faculty of Engineering Mahanakorn University of Technology Department of Mechanical Engineering Faculty of Engineering King Mongkut's Institute of Technology Ladkrabang

Effects of insertion of tandem wire coil elements used as turbulator on heat transfer and turbulent flow friction characteristics in a uniform heat-flux square duct are experimentally investigated in this work. The experiment is conducted for turbulent flow with the Reynolds number from 4000 to 25000. The wire coil element is inserted into the duct with a view to generating a swirl flow that assists to wash up the flow trapped in the duct corners and then increase the heat transfer rate of the test duct. Apart from the full-length coil, 1D and 2D length coil elements placed in tandem inside the duct with various free-space lengths are introduced to reduce the friction loss. The results obtained from these wire coil element inserts are also compared with those from the smooth duct. The experimental results reveal that the use of wire coil inserts for the full-length coil, 1D and 2D coil elements with a short free-space length leads to a considerable increase in heat transfer and friction loss over the smooth duct with no insert. The full-length wire coil provides higher heat transfer and friction factor than the tandem wire coil elements under the same operating conditions. Also, performance evaluation criteria to assess the real benefits in using the wire coil insert into the square duct are determined.

关键词： heat transfer wire coil insert square duct turbulator

Thermohydraulics of Turbulent Flow Through Heat Exchanger Tubes Fitted with Circular-rings and Twisted Tapes

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Chinese Journal of Chemical Engineering 2013年第6期21卷 585-593页

作者： smith Eiamsa-ard Vichan Kongkaitpaiboon Kwanchai Nanan Department of Mechanical Engineering Faculty of Engineering Mahanakom University of Technology Bangkok10530 Thailand

The influences of circular-ring turbulators （CRT） and twisted tape （TT） swirl generators on the heat transfer enhancement, pressure drop and thermal performance factor characteristics in a round tube are reported. The circular-ring turbulators were individually employed and together with the twisted tape swirl generators in the heated section of the tube. Three different pitch ratios （I/D = 1.0, 1.5, and 2.0） of the CRT and three different twist ratios （y/W= 3, 4, and 5） of the TT were introduced. The experiments were conducted using air as the working fluid under a uniform wall heat flux condition, for the Reynolds number between 6000 and 20000. The experimental results reveal that the heat transfer rate, friction factor and thermal performance factor of the combined CRT and qT are considerably higher than those of CRT alone. For the range examined, the Sncreases of mean Nusselt number, friction factor and thermal performance, in the tube equipped with combined devices, respectively, are 25.8%, 82.8% and 6.3% over those in the tube with the CRT alone. The highest thermal performance factor of 1.42 is found for the combined device consisting of the CRT with l/D = 1.0 and TT with y/W= 3. The correlations of the Nusselt number, friction factor and thermal performance factor of the tubes with combined devices are also developed in terms of Reynolds number, Prandtl number, twist ratio and pitch ratio.

关键词： heat transfer enhancement circular-ring twisted tape swirl generator turbulator heat exchanger

Heat transfer in turbulent tube flow inserted with loose-fit multi-channel twisted tapes as swirl generators

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Theoretical & Applied Mechanics Letters 2017年第6期7卷 372-378页

作者： Suttisak Kunlabud Varesa Chuwattanakul Vichan Kongkaitpaiboon Pitak Promthaisong smith Eiamsa-ard Faculty of Engineering Mahanakorn University of TechnologyBangkokThailand Faculty of Engineering King Mongkut's Institute of Technology LadkrabangBangkokThailand

Heat transfer and flow behaviors in three-dimensional circular tubes with loose-fit multiple channel twisted tapes were numerically studied. The investigation was examined for Reynolds numbers （Re） ranging from 5000 to 15,000, by using air as testing fluid. Effects of the multiple channel number （N = 2, 3, and 4）, clearance ratio （CR = 0.0, 0.025, 0.05, and 0.075） on heat transfer enhancement and flow friction were examined. The numerical results indicate that the tubes with loose-fit multiple channel twisted tapes perform higher heat transfer rates than the plain tube. The enhanced heat transfer rate is escorted with larger pressure drop. Both heat transfer and pressure drop increase with increasing multiple channel number （N） and decreasing clearance ratio （CR）. Heat transfer augmented by the loose-fit multiple channel twisted tape with N = 4 is higher than those enhanced by the ones with N = 2 and 3 by around 9.5-17.8% and 5.8-7.8%, respectively. In addition, the loose-fit multiple channel twisted tapes with clearance ratio of 0.025, 0.05, and 0.075 give lower heat transfer rates than the one with CR = 0.0 by around 8.4%, 17.5%, and 28.8%, respectively.

关键词： Heat transfer Heat transfer enhancement Loose-fit multiple channel twisted tape Swirling flow

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HTML5未来展望

程序员 2011年第4期 61-64页

作者： Peter Lubbers ric smith Frank Salim Brian Albers

我们将讨论一些还不够成熟但却极具潜力的HTML5特性。

关键词： HTML5 网络浏览器计算机网络网络协议

Global Wheat Head Detection 2021:An Improved Dataset for Benchmarking Wheat Head Detection Methods

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Plant Phenomics 2021年第1期3卷 277-285页

作者： Etienne David Mario Serouart Daniel smith Simon Madec Kaaviya Velumani Shouyang Liu Xu Wang Francisco Pinto Shahameh Shafiee Izzat SATahir Hisashi Tsujimoto Shuhei Nasuda Bangyou Zheng Norbert Kirchgessner Helge Aasen Andreas Hund Pouria Sadhegi-Tehran Koichi Nagasawa Goro Ishikawa Sébastien Dandrifosse Alexis Carlier Benjamin Dumont Benoit Mercatoris Byron Evers Ken Kuroki Haozhou Wang Masanori Ishii Minhajul ABadhon Curtis Pozniak David Shaner LeBauer Morten Lillemo Jesse Poland Scott Chapman Benoit de Solan Frédéric Baret Ian Stavness Wei Guo Arvalis Institut du Végétal3 Rue Joseph et Marie Hackin75116 ParisFrance UMR1114 EMMAH INRAECentre PACABâtiment ClimatDomaine Saint-Paul228 Route de l’AérodromeCS 4050984914 Avignon CedexFrance School of Food and Agricultural Sciences The University of QueenslandGatton4343 QLDAustralia Hiphen SAS 120 Rue Jean DaussetAgroparcBâtiment Technicité84140 AvignonFrance Plant Phenomics Research Center Nanjing Agricultural UniversityNanjingChina Wheat Genetics Resource Center Dep.of Plant PathologyKansas State Univ.4024 Throckmorton Plant Sciences CenterManhattanKansasUSA Global Wheat Program International Maize and Wheat Improvement Centre(CIMMYT)MexicoD.F.Mexico Faculty of Biosciences Norwegian University of Life SciencesP.O.Box 5003NO-1432ÅsNorway Agricultural Research Corporation Wheat Research ProgramP.O.Box 126Wad MedaniSudan Arid Land Research Center Tottori UniversityTottori 680-0001Japan Laboratories of Plant Genetics and Plant Breeding Graduate School of AgricultureKyoto UniversityJapan CSIRO Agriculture and Food Queensland Biosciences Precinct306 Carmody RoadSt Lucia4067 QLDAustralia Institute of Agricultural Sciences ETH ZurichUniversitätstrasse 28092 ZurichSwitzerland Plant Sciences Department Rothamsted ResearchHarpendenUK Institute of Crop Science National Agriculture and Food Research OrganizationJapan Hokkaido Agricultural Research Center National Agriculture and Food Research OrganizationJapan Biosystems Dynamics and Exchanges TERRA Teaching and Research CenterGembloux Agro-Bio TechUniversity of Liège5030 GemblouxBelgium Plant Sciences TERRA Teaching and Research CenterGembloux Agro-Bio TechUniversity of Liège5030 GemblouxBelgium Graduate School of Agricultural and Life Sciences The University of Tokyo1-1-1 Midori-choNishitokyo CityTokyoJapan Department of Computer Science University of SaskatchewanCanada Department of Plant Sciences University of SaskatchewanCanada College of Agriculture and Life Sciences University of ArizonaTucsonArizona

The Global Wheat Head Detection(GWHD)dataset was created in 2020 and has assembled 193,634 labelled wheat heads from 4700 RGB images acquired from various acquisition platforms and 7 countries/*** an associated competition hosted in Kaggle,GWHD_2020 has successfully attracted attention from both the computer vision and agricultural science *** this first experience,a few avenues for improvements have been identified regarding data size,head diversity,and label *** address these issues,the 2020 dataset has been reexamined,relabeled,and complemented by adding 1722 images from 5 additional countries,allowing for 81,553 additional wheat *** now release in 2021 a new version of the Global Wheat Head Detection dataset,which is bigger,more diverse,and less noisy than the GWHD_2020 version.

关键词： Wheat adding release