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Boiling heat transfer correlations for refrigerant mixtures flowing inside micro-fin tubes

ZHANG Xiaoyan, ZHANG Xingqun, CHEN Yunguang, YUAN Xiuling

《能源前沿（英文）》 2008年 第2卷 第4期   页码 489-493 doi: 10.1007/s11708-008-0110-6

摘要： Based on experimental results of ternary non-azeotropic refrigerant mixture R417A flowing and boiling in one smooth and two internally grooved horizontal tubes with different geometrical parameters, a boiling heat transfer correlations was developed for refrigerant mixtures flowing inside micro-fin tubes by applying the enhancement factor in the present modified-Kattan model which was modified by the experimental data of R417A in a smooth tube. The comparison between the calculation and the experimental results indicates that the prediction by the present correlations is in good agreement with the experiment of refrigerant mixtures inside different micro-fin tubes with a standard deviation of ± 30% for vapor qualities below 80%.

关键词： comparison     micro-fin     calculation     transfer     prediction    

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Experimental study of heat transfer coefficient with rectangular baffle fin of solar air heater

Foued CHABANE,Nesrine HATRAF,Noureddine MOUMMI

《能源前沿（英文）》 2014年 第8卷 第2期   页码 160-172 doi: 10.1007/s11708-014-0321-y

摘要： This paper presents an experimental analysis of a single pass solar air collector with, and without using baffle fin. The heat transfer coefficient between the absorber plate and air can be considerably increased by using artificial roughness on the bottom plate and under the absorber plate of a solar air heater duct. An experimental study has been conducted to investigate the effect of roughness and operating parameters on heat transfer. The investigation has covered the range of Reynolds number from 1259 to 2517 depending on types of the configuration of the solar collectors. Based on the experimental data, values of Nusselt number have been determined for different values of configurations and operating parameters. To determine the enhancement in heat transfer and increment in thermal efficiency, the values of Nusselt have been compared with those of smooth duct under similar flow conditions.

关键词： Nusselt number     flow rate     heat transfer     heat transfer coefficient     thermal efficiency     forced convection    

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Research on swimming by undulatory long dorsal fin propulsion

WANG Guangming, SHEN Lincheng, WU Yonghui

《机械工程前沿（英文）》 2007年 第2卷 第1期   页码 77-81 doi: 10.1007/s11465-007-0013-y

摘要： The kinematics of steady forward swimming of is described. The geometric features of the body and locomotive characteristic and parameters of the flexible dorsal fin are discussed. On the basis of observation and experimental data, a simplified kinematic model on locomotion of the undulatory long dorsal fin propulsion is promoted. The hydromechanical performances of the undulatory long dorsal fin propeller of are estimated with the large-amplitude elongated-body theory. The hydromechanical efficiency of the undulatory long dorsal fin system ranged from 81.664% to 86.420% over a speed range of 0.728 0.985 length " s. It is suggested that the undulatory long dorsal fin propulsion is an adaptation to swimming with high hydromechanical efficiency.

关键词： locomotive characteristic     hydromechanical     observation     propulsion     hydromechanical efficiency    

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Flow and heat transfer in compact offset strip fin surfaces

DONG Junqi, CHEN Jiangping, CHEN Zhijiu

《能源前沿（英文）》 2008年 第2卷 第3期   页码 291-297 doi: 10.1007/s11708-008-0061-y

摘要： Experimental studies of air-side heat transfer and pressure drop characteristics of offset strip fins and flat tube heat exchangers were performed. A series of tests were conducted for 9 heat exchangers with different fin space, fi

关键词： different     air-side     transfer     pressure     offset    

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Creep of brazed plate-fin structures in high temperature compact heat exchangers

Shantung TU, Guoyan ZHOU

《机械工程前沿（英文）》 2009年 第4卷 第4期   页码 355-362 doi: 10.1007/s11465-009-0065-2

摘要： In recent years, the need for high temperature heat exchangers to improve the efficiency of power and chemical conversion systems has been growing. However, the creep design of the high temperature compact heat exchangers has been a primary concern because the working temperature can be well above the creep limit of the materials. To establish the high temperature design criterion for compact heat exchangers, creep behavior of the plate-fin structures and brazed joints are investigated in this paper. The time-dependent deformation and bending stress of the plate-fin structures are obtained analytically by simplifying the fins to elastic springs. The creep damage evolution inside the brazed joint is studied by coupling the finite element method with a damage constitutive equation. The significant effect of creep property mismatch in the brazed joint on the creep strength is demonstrated.

关键词： compact heat exchanger     creep     damage     brazing joint    

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Thermal-hydraulic performance of novel louvered fin using flat tube cross-flow heat exchanger

DONG Junqi, CHEN Jiangping, CHEN Zhijiu

《能源前沿（英文）》 2008年 第2卷 第1期   页码 99-106 doi: 10.1007/s11708-008-0010-9

摘要： Experimental studies were conducted to investigate the air-side heat transfer and pressure drop characteristics of a novel louvered fins and flat tube heat exchangers. A series of tests were conducted for 9 heat exchangers with different fin space and fin length, at a constant tube-side water flow rate of 2.8 m/h. The air side thermal performance data were analyzed using the effectiveness-NTU method. Results were presented as plot of Colburn factor and friction factor against the Reynolds number in the range of 500–6500. The characteristics of the heat transfer and pressure drop of different fin space and fin length were analyzed and compared. In addition, the curves of the heat transfer coefficients vs. pumping power per unit heat transfer area were plotted. Finally, the area optimization factor was used to evaluate the thermal hydraulic performance of the louvered fins with differential geometries. The results showed that the and factors increase with the decrease of the fin space and fin length, and the fin space has more obvious effect on the thermal hydraulic characteristics of the novel louvered fins.

关键词： obvious effect     different     thermal hydraulic     constant tube-side     Colburn    

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Flexible micro flow sensor for micro aerial vehicles

Rong ZHU, Ruiyi QUE, Peng LIU

《机械工程前沿（英文）》 2017年 第12卷 第4期   页码 539-545 doi: 10.1007/s11465-017-0427-0

摘要：

This article summarizes our studies on micro flow sensors fabricated on a flexible polyimide circuit board by a low-cost hybrid process of thin-film deposition and circuit printing. The micro flow sensor has merits of flexibility, structural simplicity, easy integrability with circuits, and good sensing performance. The sensor, which adheres to an object surface, can detect the surface flow around the object. In our study, we install the fabricated micro flow sensors on micro aerial vehicles (MAVs) to detect the surface flow variation around the aircraft wing and deduce the aerodynamic parameters of the MAVs in flight. Wind tunnel experiments using the sensors integrated with the MAVs are also conducted.

关键词： micro flow sensor     flexible sensor     surface flow sensing     aerodynamic parameter     micro aerial vehicle (MAV)    

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A new performance evaluation method and its application in fin-tube surface design of small diameter

Jufang FAN, Weikun DING, Zhigeng WU, Yaling HE, Wenquan TAO, Yongxin ZHENG, Yifeng GAO, Ji SONG

《能源前沿（英文）》 2011年 第5卷 第1期   页码 59-68 doi: 10.1007/s11708-010-0132-8

摘要： In this paper, a simple yet efficient performance comparison method is proposed based on the assumptions of constant properties and identical frontal area. For this method, no correlations are required, and a small number of discrete data are sufficient. To illustrate the feasibility of the proposed approach, a new slotted fin with 4 mm tubes is designed to replace the original louvered fin with tubes of 7 mm. The orthogonal design method is adopted in the fin design to reduce the number of computational cases significantly, and yet a nearly optimum combination of major geometric factors can still be obtained. The reasonable parametric combination of 3 global parameters is obtained by analyzing the numerical results of 16 plain plate fins. Based on this result, 3 new slotted fins with different fin pitches are studied. The slotted fin with a fin pitch of 1.4 mm is recommended after considering the heat transfer, comprehensive performance, and cost of material and operation. The result shows that compared with the original louvered fin, the recommended fin not only increases the heat transfer rate by 2.2%, 22.5%, and 13.7% under an identical flow rate, identical pressure drop, and identical pumping power constraint, respectively, but also saves approximately 36% of the copper tube materials.

关键词： performance evaluation     orthogonal design     small-diameter tube    

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Transversal tube pitch effects on local heat transfer characteristics of the flat tube bank fin mountedvortex generators and their sensitivity to nonuniform temperature of the fin

Liangbi WANG, Zhimin LIN, Kangjie SUN, Yuanxin DONG, Song LIU, Yongheng ZHANG,

《能源前沿（英文）》 2010年 第4卷 第3期   页码 333-345 doi: 10.1007/s11708-009-0061-6

摘要： The tube bank fin is commonly used to increase the area of the heat transfer surface with a small heat transfer coefficient of a heat exchanger. If vortex generators (VGs) are punched on the fin surface, the heat transfer performance of the fin can be improved. This paper focused on the effect of transversal tube pitch on the local heat transfer performance of the three-row flat tube bank fin mounted with VGs. On the fin surface, constructing the flow channel but without mounted VGs, the transversal tube pitch was greater, and the span averaged Nusselt number downstream was larger because fewer interactions of vortices would be generated from different VGs located upstream. When the area goodness factor was used as the criteria on the condition of one tube unit of heat exchanger for commonly used fin materials and fin thickness, the transversal tube pitch has considerable effect on the heat transfer enhancement of VGs. Large transversal tube pitch is more sensitive to fin material than to fin thickness.

关键词： heat transfer enhancement     vortex generator     finned flat tube bank     heat exchanger    

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Dependence of error sensitivity of frequency on bias voltage in force-balanced micro accelerometer

Lili CHEN, Wu ZHOU

《机械工程前沿（英文）》 2013年 第8卷 第2期   页码 146-149 doi: 10.1007/s11465-013-0260-z

摘要：

To predict more precisely the frequency of force-balanced micro accelerometer with different bias voltages, the effects of bias voltages on error sensitivity of frequency is studied. The resonance frequency of accelerometer under closed loop control is derived according to its operation principle, and its error sensitivity is derived and analyzed under over etching structure according to the characteristics of Deep Reaction Ion Etching (DRIE). Based on the theoretical results, micro accelerometer is fabricated and tested to study the influences of AC bias voltage and DC bias voltage on sensitivity, respectively. Experimental results indicate that the relative errors between test data and theory data are less than 7%, and the fluctuating value of error sensitivity under the range of voltage adjustment is less than 0.01 μm . It is concluded that the error sensitivity with designed parameters of structure, circuit and process error can be used to predict the frequency of accelerometer with no need to consider the influence of bias voltage.

关键词： Micro-Electro-Mechanical Systems (MEMS)     micro accelerometer     force-balanced micro accelerometer     frequency     error sensitivity    

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Numerical simulation of micro scale flowing and boiling

Wen WANG, Rui ZHUAN,

《能源前沿（英文）》 2009年 第3卷 第4期   页码 396-401 doi: 10.1007/s11708-009-0049-2

摘要： Numerical simulations of flowing and boiling in micro channels are presented, including the modeling of bubble dynamics of nucleate boiling, and a description of the interface of two phases with the volume-of-fluid (VOF). The two calculated cases are compared with related experimental data in literature. Some simulated results are found corresponding well to the experimental data. The simulated results also show the details of 3-dimensional heat transfer and the flow in micro channels, which are helpful to the investigation of the mechanism of two-phase heat transfer and flow in micro channels.

关键词： volume-of-fluid (VOF)     micro channel     nucleate boiling     bubble dynamics     simulation    

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Dynamical research on spherical micro actuator with piezoelectric ceramic stacks drivers

ZHANG Ruihua, CHEN Haichu

《机械工程前沿（英文）》 2007年 第2卷 第4期   页码 433-438 doi: 10.1007/s11465-007-0074-y

摘要： This paper develops a 30 mm × 30 mm × 50 mm spherical micro actuator driven by piezoelectric ceramic stacks (PZT), and analyzes its dynamic performances. First, the space coordinate relationship of the spherical micro actuator and a dynamic model are set up. Second, The Runge-Kutta arithmetic is used to calculate the dynamical parameters of the micro actuator; the SIMULINK module of MATLAB is used to build the dynamical simulating model and then simulate it. Third, an experimental sample of the spherical micro actuator is developed, a micromanipulator is integrated with a micro-gripper based on the sample spherical micro actuator, and the experimental research on the micro assembly is conducted between a micro shaft of 180 μm and a micro spindle sleeve of 200 μm. Finally, the characteristics of the spherical micro actuator influenced by the mass of the metal sphere of the micro actuator, driving signal frequency, friction coefficient of the contact surface between the metal sphere and the friction block of the micro driving unit are analyzed. The experimental results indicate that the rotation resolution of the micro actuator reaches 0.000 1°, the rotation positioning precision reaches 0.000 5°, and the maximum working frequency is about 1200 Hz. The experimental results validate the back rotation vibration model of the spherical micro actuator. The micromanipulator integrated by the spherical micro actuator can meet the requirements of precise micro operation and assembly for micro electro mechanical systems (MEMS) or other microelements in micro degree fields.

关键词： spherical     micro-gripper     friction coefficient     dynamic     frequency    

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Laboratory assessment of Alaska aggregates using Micro-Deval test

Jenny LIU,Sheng ZHAO,Anthony MULLIN

《结构与土木工程前沿（英文）》 2017年 第11卷 第1期   页码 27-34 doi: 10.1007/s11709-016-0359-5

摘要： Aggregates suitable for use in asphalt concrete (AC) pavement construction must meet durability criteria. Thus, it is critical to select appropriate tests to properly characterize aggregate durability. In Alaska, durability tests currently being used for aggregates in AC pavement include Los Angeles (LA) abrasion test, sulfate soundness test and Washington degradation test. However, there have long been concerns arising over Washington degradation test used as an acceptance tool, motivating pavement practitioners to seek more suitable alternatives. This paper presents a study to investigate the feasibility of using Micro-Deval test, commonly used in other states, to evaluate the durability of Alaskan aggregates in AC pavement as well as its potential to replace Washington degradation test. Micro-Deval test, Washington degradation test and other tests currently specified in Alaska were conducted on aggregates from 16 batches representing statewide sources. Based on the testing results, it is found that using Micro-Deval test for durability assessment of Alaska aggregates was feasible and reproducible, and a high potential was revealed to use Micro-Deval test to replace Washington degradation test in Alaska. It is recommended that Micro-Deval test be considered as an additional test for a certain period, but in the long run should be used along with current LA abrasion and sulfate soundness tests to provide a more desirable durability assessment of Alaska aggregates used in AC pavement.

关键词： aggregate durability     Washington degradation test     Micro-Deval test    

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Characterization of micro-mixing in a novel impinging streams reactor

Hui HU, Zhiming CHEN, Zhen JIAO

《化学科学与工程前沿（英文）》 2009年 第3卷 第1期   页码 58-64 doi: 10.1007/s11705-009-0106-8

摘要： This paper presents an experimental investigation of a novel impinging stream reactor (ISR) with the aim of high mixing intensity. The integral mixing quality in the reactor was measured with the iodide-iodate reaction and showed excellent mixing performance. The impact of the operating parameters, such as fluxes, circulation and inter-nozzle distances, was investigated in terms of segregation index. The results showed that the increase of flux, the decrease of inter-nozzle distance and a suitable circulation can improve the micro-mixing efficiency. Based on turbulence theory, it was estimated that the characteristic micro-mixing time was 0.002—0.02 s, which was much shorter than that in the stirred tank reactor. The micro-mixing time was related to the segregation index, which was in good agreement with those in the literature.

关键词： micro-mixing     impinging streams reactor     turbulent mixing     mass transfer    

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Recent advances in micro- and nano-machining technologies

Shang GAO, Han HUANG

《机械工程前沿（英文）》 2017年 第12卷 第1期   页码 18-32 doi: 10.1007/s11465-017-0410-9

摘要：

Device miniaturization is an emerging advanced technology in the 21st century. The miniaturization of devices in different fields requires production of micro- and nano-scale components. The features of these components range from the sub-micron to a few hundred microns with high tolerance to many engineering materials. These fields mainly include optics, electronics, medicine, bio-technology, communications, and avionics. This paper reviewed the recent advances in micro- and nano-machining technologies, including micro-cutting, micro-electrical-discharge machining, laser micro-machining, and focused ion beam machining. The four machining technologies were also compared in terms of machining efficiency, workpiece materials being machined, minimum feature size, maximum aspect ratio, and surface finish.

关键词： micro machining     cutting     electro discharge machining (EDM)     laser machining     focused ion beam (FIB)    

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标题 作者 时间 类型 操作

Boiling heat transfer correlations for refrigerant mixtures flowing inside micro-fin tubes

ZHANG Xiaoyan, ZHANG Xingqun, CHEN Yunguang, YUAN Xiuling

期刊论文

Experimental study of heat transfer coefficient with rectangular baffle fin of solar air heater

Foued CHABANE,Nesrine HATRAF,Noureddine MOUMMI

期刊论文

Research on swimming by undulatory long dorsal fin propulsion

WANG Guangming, SHEN Lincheng, WU Yonghui

期刊论文

Flow and heat transfer in compact offset strip fin surfaces

DONG Junqi, CHEN Jiangping, CHEN Zhijiu

期刊论文

Creep of brazed plate-fin structures in high temperature compact heat exchangers

Shantung TU, Guoyan ZHOU

期刊论文

Thermal-hydraulic performance of novel louvered fin using flat tube cross-flow heat exchanger

DONG Junqi, CHEN Jiangping, CHEN Zhijiu

期刊论文

Flexible micro flow sensor for micro aerial vehicles

Rong ZHU, Ruiyi QUE, Peng LIU

期刊论文

A new performance evaluation method and its application in fin-tube surface design of small diameter

Jufang FAN, Weikun DING, Zhigeng WU, Yaling HE, Wenquan TAO, Yongxin ZHENG, Yifeng GAO, Ji SONG

期刊论文

Transversal tube pitch effects on local heat transfer characteristics of the flat tube bank fin mountedvortex generators and their sensitivity to nonuniform temperature of the fin

Liangbi WANG, Zhimin LIN, Kangjie SUN, Yuanxin DONG, Song LIU, Yongheng ZHANG,

期刊论文

Dependence of error sensitivity of frequency on bias voltage in force-balanced micro accelerometer

Lili CHEN, Wu ZHOU

期刊论文

Numerical simulation of micro scale flowing and boiling

Wen WANG, Rui ZHUAN,

期刊论文

Dynamical research on spherical micro actuator with piezoelectric ceramic stacks drivers

ZHANG Ruihua, CHEN Haichu

期刊论文

Laboratory assessment of Alaska aggregates using Micro-Deval test

Jenny LIU,Sheng ZHAO,Anthony MULLIN

期刊论文

Characterization of micro-mixing in a novel impinging streams reactor

Hui HU, Zhiming CHEN, Zhen JIAO

期刊论文

Recent advances in micro- and nano-machining technologies

Shang GAO, Han HUANG

期刊论文