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Heat Transfer and Resistance Characteristics of Conical Spiral Tube Bundle Based on field synergy principle

Chinese Journal of Mechanical Engineering 2012年第2期25卷 370-376页

作者： YAN Ke GE Peiqi HU Ruirong MENG Haitao School of Mechanical Engineering Shandong UniversityJinan 250061China Key Laboratory of High Efficiency and Clean Mechanical Manufacture of Ministry of Education Shandong UniversityJinan 250061China

Conical spiral tube bundle are universally used in heat transfer enhancement in heat *** heat transfer and resistance of the tube bundle are affected greatly by the conical structure,so the analysis of it is *** order to a further evaluation,the heat transfer and resistance characteristics of conical spiral tube bundle are investigated with regression analysis based on numerical simulation *** correlations of heat transfer and pressure drop of conical spiral tube bundle are proposed both in laminar and turbulent fluid *** the based of the field synergy principle,the synergy of four vectors,the velocity,the velocity gradient,the temperature gradient and the pressure gradient,are calculated and discussed via the user defined function（UDF） *** synergy angles β and θ,which respectively denote the performance of heat transfer enhancement and pressure drop of the conical spiral tube bundle,are ***,the comprehensive performance of the conical spiral tube is evaluated by the synergy angle γ and all of the three synergy angles of conical spiral tube bundle are compared to both bare tube and thin cylinder-interpolated *** analysis of the synergy angles shows that the heat transfer enhancement and pressure drop of conical spiral tube bundle are smaller than that of the thin cylinder-interpolated tube,while the comprehensive performance of conical spiral tube bundle is *** analysis of the heat transfer and pressure drop of conical spiral tube is valuable and instructional on the design and optimum of conical spiral tube bundle heat exchangers.

关键词： conical spiral tube bundle field synergy principle regression analysis

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Flow characteristics of tangential leakage in a scroll compressor for automobile heat pump with CO_(2)

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Science China(Technological Sciences) 2021年第5期64卷 971-983页

作者： ZHENG SiYu WEI MingShan HU ChenXing SONG PanPan TIAN Ran School of Mechanical Engineering Beijing Institute of TechnologyBeijing 100081China

Tangential leakage loss reduction has great significance on improving the performance of scroll *** this study,the flow field of a scroll compressor working with CO_(2) was numerically *** development characteristics of the tangential leakage flow in different working chambers were carried out,which was obtained by analyzing the field quantities *** impacts of the radial clearances and sidewall roughness on the tangential leakage were also taken into consideration,in order to explore the feasible method of the flow control for the tangential leakage in scroll *** showed that the tangential leakage flow had various characteristics in the suction and compression chambers due to the different interactions between the tangential leakage flow and *** to little reverse pressure gradient,the tangential leakage flow maintained the typical jet form in the suction *** contrast,the mixing of the tangential leakage flow and mainstream induced the passage vortex and secondary flows in the compression *** secondary flow was the primary factor that results in the occurrence of localized high temperature region rather than the tangential *** the increase of the radial clearance,the volumetric efficiency declined and the discharge temperature increased *** terms of flow control of the tangential leakage,the increase of sidewall roughness by 2μm could achieve the same effect as the decrease of the radial clearance by 4μm,while the volumetric efficiency increased by almost 5%and average discharge temperature decreased by 5K.

关键词： carbon dioxide scroll compressor field synergy principle tangential leakage sidewall roughness

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Enhanced Heat Transfer of Carbon Nanotube Nanofluid Microchannels Applied on Cooling Gallium Arsenide Cell

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Journal of Thermal Science 2020年第6期29卷 1475-1486页

作者： ZHANG Huiying YAN Suying WANG Tao WU Yuting ZHAO Xiaoyan ZHAO Ning College of Energy and Power Engineering Inner Mongolia University of TechnologyHohhot 010051China College of Environmental and Energy Engineering Beijing University of TechnologyBeijing 100124China

Carbon nanotube nanofluids have wide application prospects due to their unique structure and excellent *** this study,the thermal conductivity properties of carbon nanotube nanofluids and SiO2/water nanofluids were compared and analyzed experimentally using different preparation *** physical properties of nanofluids were tested using a Malvern Zetasizer Nano Instrument and a Hot Disk Thermal Constant *** with field synergy theory analysis of the heat transfer performance of nanofluids,results show that the thermal conductivity of carbon nanotube nanofluids is higher than that of SiO2/water nanofluids,and the thermal conductivity of nanofluid rises with the increase of mass fraction and ***,the synergistic performance of carbon nanotube nanofluids is also superior to that of SiO2/water *** the mass fraction of the carbon nanotube nanofluids is 10%and the SiO2/water nanofluids is 8%,their field synergy numbers and heat transfer enhancement factors both reach *** the perspective of the preparation method,the thermal conductivity of nanofluids dispersed by high shear microfluidizer is higher than that by ultrasonic *** result provides some reference for the selection and use of working substance in a microchannel cooling concentrated photovoltaic and thermal(CPV/T)system.

关键词： concentrated photovoltaic solar cell thermal conductivity carbon nanotube nanofluids field synergy principle heat transfer property

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Heat Transfer and Flow Resistance Characteristics of Helical Baffle Heat Exchangers with Twisted Oval Tube

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Journal of Thermal Science 2022年第2期31卷 370-378页

作者： GU Xin ZHENG Zhiyang XIONG Xiaochao JIANG Erhui WANG Tongtong ZHANG Dongwei School of Mechanical and Power Engineering Zhengzhou UniversityZhengzhou 450001China

To overcome the defect of the significant increase in pressure drop when the heat transfer performance of helical baffle heat exchanger is improved,a novel helical baffle heat exchanger with twisted oval tube is *** simulation was done to exhibit the shell side heat transfer and flow characteristics with CFD software *** field synergy principle was used to evaluate the shell side *** results show that the flow velocity distribution on the shell side of the spiral baffle heat exchanger is more uniform and the velocity near the tube wall increases in the range of research parameters,as the circular tube is replaced by a twisted elliptical tube with the same perimeter ***,the helical baffle heat exchanger with twisted oval tube has better field synergy of velocity and temperature gradient,velocity and pressure *** helical baffle heat exchanger with helix angle of 15°has better performance than that of circular tube,and its heat transfer coefficient is improved about 3.3%and pressure drop is reduced by 17.1%–19.1%.Hence,the comprehensive heat transfer performance is improved by 21.5%–22.5%.When the helix angle is 20°,the comprehensive heat transfer performance is increased by 16.1%–18.0%with heat transfer coefficient improvement of 3.6%and pressure drop reduction of 13.9%–16.5%.

关键词： twisted oval tube helical baffle field synergy principle heat transfer enhancement

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Constructal design progress for eight types of heat sinks

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Science China(Technological Sciences) 2020年第6期63卷 879-911页

作者： CHEN LinGen YANG AiBo FENG HuiJun GE YanLin XIA ShaoJun Institute of Thermal Science and Power Engineering Wuhan Institute of TechnologyWuhan 430205China School of Mechanical&Electrical Engineering Wuhan Institute of TechnologyWuhan 430205China The 91404 Unit of PLA Qinhuangdao 066001China

This review paper summarizes constructal design progress performed by the authors for eight types of heat sinks with ten performance indexes being taken as the optimization objectives,respectively,by combining the methods of theoretical analysis and numerical *** eight types of heat sinks are uniform height rectangular fin heat sink,non-uniform height rectangular fin heat sink,inline cylindrical pin-fin heat sink(ICPHS),plate single-row pin fin heat sink(PSRPHS),plate inline pin fin heat sink(PIPHS),plate staggered pin fin heat sink(PSPHS),single-layered microchannel heat sink(SLMCHS)with rectangular cross sections and double-layered microchannel heat sink(DLMCHS)with rectangular cross sections,*** the ten performance indexes are heat transfer rate maximization,maximum thermal resistance minimization,minimization of equivalent thermal resistance which is defined based on the entransy dissipation rate(equivalent thermal resistance for short),field synergy number maximization,entropy generation rate minimization,operation cost minimization,thermo-economic function value minimization,pressure drop minimization,enhanced heat transfer factor maximization and efficiency evaluation criterion number maximization,*** optimal constructs of the eight types of heat sinks with different constraints and based on the different optimization objectives are compared with each *** results indicated that the optimal constructs mostly are different based on different optimization objectives under the same boundary *** optimization objective should be suitable chosen based on the focus when the constructal design for one heat sink is *** results obtained herein have some important theoretical significances and application values,and can provide scientific bases and theoretical guidelines for the thermal design of real heat sinks and their applications.

关键词： constructal theory entropy generation minimization principle field synergy principle extremum principle of entransy dissipation generalized thermodynamic optimization multi-objective optimization of heat sinks

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Characteristics of Fluid Flow and Heat Transfer in the Shell Side of the Trapezoidal-like Tilted Baffles Heat Exchanger

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Journal of Thermal Science 2018年第6期27卷 602-610页

作者： GU Xin ZHENG Zhiyang XIONG Xiaochao WANG Tongtong LUO Yuankun WANG Ke Key Laboratory of Process Heat Transfer and Energy Saving of Henan Province Zhengzhou University

Periodic whole cross-section computation models are established for segmental baffle heat exchanger, shutter baffle heat exchanger, and trapezoid-like tilted baffle heat exchanger. The reliability of models is verified by comparing the simulated results to the results obtained from the Bell-Delaware method. Due to the orthogonal assembly of the baffles, the shell side fluid shows the twisty flow of trapezoid-like tilted baffle heat exchanger. The essential mechanism on disturbing flow and heat transfer enhancement is revealed by defining the non-dimensional factor η of the shell side fluid flow direction of heat exchanger and the field synergy principle. The results show that at the same Reynolds number, the shell side fluid convection heat transfer coefficient of trapezoid-like tilted baffle heat exchanger is 12.43%-24.33% and 6.71%-11.51% higher than those of segmental baffle heat exchanger and shutter baffle heat exchanger, respectively. The shell side fluid flow velocity field and the pressure gradient field of trapezoid-like tilted baffle heat exchanger and shutter baffle heat exchanger decreases compared with that of segmental baffle heat exchanger, so the shell side fluid flow resistance and pressure drop is increased; the shell side comprehensive performance of trapezoid-like tilted baffle heat exchanger is 5.85%-9.06% higher than that of segmental baffle heat exchanger, and 15.27%-23.28% higher than that of shutter baffle heat exchanger. In this study, a baffle structure with higher efficiency of the energy utilization for the heat exchanger is provided.

关键词： shell-and-tube heat exchanger trapezoid-like tilted baffle twisty flow field synergy principle

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Simulation, experimentation, and collaborative analysis of adjacent heat exchange modules in a vehicular cooling system

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2013年第6期14卷 417-426页

作者： Yu-qi HUANG Rui HUANG Xiao-li YU Feng LV Power Machinery and Vehicular Engineering Institute Zhejiang University Department of Mechanical and Aerospace Engineering Monash University-Clayton

A cooling system consisting of several heat exchange modules is a necessary part of an automobile, and its performance has a direct effect on a vehicle's energy consumption. Heat exchangers, such as a charged air cooler (CAC), radiator, oil cooler, or condenser have different structures and can be arranged in various orders, and each combination may produce different effects because of interactions among them. In this study, we aimed to explore the principles governing interactions among adjacent heat exchangers in a cooling system, using numerical simulation and experimental technology. 3D models with different combinations were developed, compared, and analyzed comprehensively. A wind tunnel test platform was constructed to validate the computational results. We found that the heat dissipation of the modules was affected slightly by their relative position (the rules basically comply with the field synergy principle), but was independent of the modules' spacing within a certain distance range. The heat dissipation of one module could be effectively improved by restructuring, but with a penalty of higher resistance. However, the negative effect on the downstream module was much less than expected. The results indicated that the intensity of heat transfer depends not only on the average temperature difference between cold and hot mediums, but also on the temperature distribution.

关键词： Collaborative analysis Heat exchangers field synergy principle Computational fluid dynamics (CFD) Wind tunnel

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Effects of Shape and Quantity of Helical Baffle on the Shell-side Heat Transfer and Flow Performance of Heat Exchangers

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Chinese Journal of Chemical Engineering 2014年第3期22卷 243-251页

作者：杜文静王红福程林 Institute of Thermal Science & Technology Shandong University

Shape and quantity of helical baffles have great impact on the shell-side performance of helical baffled heat exchangers （HBHE）. In this work, three physical models of HBHE with baffles of different shape （trisection, quadrant and sextant sector） were investigated. Numerical simulations were performed on HBHE at three helix an- gles （10°, 25° and 40°） by the software ANSYS CFX. Analyses of numerical results indicate that the sextant HBHE shows relatively better fluid flow performance because the leakage flow in the triangle area is evidently reduced and the fluid streamline appears much closer to an ideal spiral flow, while the trisection and quadrant HBHE show more scattered and disordered streamline distributions. The convective heat transfer coefficient and pressure drop in three types of HBHE were presented. Further investigations on the shell side performance with different helical baf- fles were implemented by the field synergy theory. Both theoretical and numerical analyses gave support on the re- lations between helical baffle shape and shell-side performance. This paper may provide useful reference for the selection of baffle shade and auantitv in HBHE.

关键词： helical baffled heat exchanger trisection quadrant sextant field synergy principle

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Experiment and numerical simulation on flow and heat transfer in all-glass evacuated tube solar collectors

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Journal of Southeast University(English Edition) 2016年第4期32卷 489-495页

作者：张涛韩吉田陈常念孔令健刘洋山东大学能源与动力工程学院济南250061

The experimental study of natural convection in allglass evacuated tube solar collectors is performed through the experimental platform of the solar-assisted fuel cell *** experimental facility includes solar collectors with different length and diameter tubes, different coating materials, and with / without guide plates, respectively. Threedimensional mathematical models on natural and forced convections in the solar collectors are established and the experimental data is validated by field synergy and entransy principles. The results of natural convection show that the water temperature increases and thermal efficiency decreases gradually with the evacuated tube length. The thermal efficiency increases when absorption rates increase from 0. 95 to 1. 0 and emission rates decrease from 0. 16 to 0. 06. The thermal efficiency of solar collectors is increased after being equipped with the guide plate, which is attributed to the disappearance of the mixed flowand the enhancement of the heat transfer at the bottom of the evacuated tube. The results of forced convertion indicate that the Reynolds, Nusselt and entransy increments of the horizontal double collectors are higher than those of the vertical single collector while the entransy dissipation is lower than that of the vertical single collector. It is concluded that the solar collectors with guide plates are suitable for natural convection while the double horizontal collectors are suitable for forced convection in the thermal field of solar-assisted fuel cell systems with lowand medium temperatures.

关键词： all-glass evacuated tube solar collectors the solar-assisted fuel cells field synergy principle entransy dissipation

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Numerical Investigation on Flow and Heat Transfer Performance of Supercritical Carbon Dioxide Based on Variable Turbulent Prandtlnumber Model

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Mechanical Engineering Science 2021年第2期3卷 1-8页

作者： Xiaokai LIU Haiyan ZHANG Keyong CHENG Xiulan HUAI Haiyan LIAO Zhongmei ZHANG Institute of Engineering Thermophysics Chinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China Nanjing Institute of Future Energy System Nanjing 210000China CHN Energy New Energy Technology Research Institute CO. LTD.Beijing 102206China

Flow and heat transfer characteristic of supercritical carbon dioxide(SCO_(2))are numerically investigated in the horizontal and vertical *** turbulent Prandtl number model could well describe the behavior of SCO_(2) affected by the *** the cooling condition,the heat transfer performance of SCO_(2) along the upward direction is best and that along the downward direction is worst when bulk fluid temperatures are below the pseudocritical *** the ratio of heat flux to mass flux could decrease the difference of convective heat transfer coefficient in three flow *** the heating condition,heat transfer deterioration only occurs in vertical upward and horizontal flow *** transfer deterioration of SCO_(2) could be delayed by increasing the mass flux and the deterioration degree is weakened in the second half of tube along the vertical upward flow *** with the straight tube,the corrugated tube shows better comprehensive thermal performance.

关键词： Supercritical carbon dioxide Turbulent Prandtl number Flow and heat transfer field synergy principle Numerical investigation

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