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Characteristics of flow and heat transfer of shell-and-tube heat exchangers with overlapped helical baffles

Tingting DU, Wenjing DU

《工程管理前沿（英文）》 2019年 第6卷 第1期   页码 70-77 doi: 10.1007/s42524-019-0005-8

摘要：

The characteristics of flow and heat transfer of shell-and-tube heat exchangers with overlapped helical baffles (STHXsHB) were illustrated through a theoretical analysis and numerical simulation. The ideal helical flow model was constructed to demonstrate parts of the flow characteristics of the STHXsHB, providing theoretical evidence of short-circuit and back flows in a triangular zone. The numerical simulation was adopted to describe the characteristics of helical, leakage, and bypass streams. In a fully developed section, the distribution of velocity and wall heat transfer coefficient has a similar trend, which presents the effect of leakage and bypass streams. The short-circuit flow accelerates the axial velocity of the flow through the triangular zone. Moreover, the back flow enhances the local heat transfer and causes the ascent of flow resistance. This study shows the detailed features of helical flow in STHXsHB, which can inspire a reasonable optimization on the shell-side structure.

关键词： heat exchanger     overlapped helical baffle     triangular zone     helical flow    

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CFD simulation on shell-and-tube heat exchangers with small-angle helical baffles

Minhua ZHANG,Fang MENG,Zhongfeng GENG

《化学科学与工程前沿（英文）》 2015年 第9卷 第2期   页码 183-193 doi: 10.1007/s11705-015-1510-x

摘要： Shell-and-tube heat exchanger with helical baffles is superior to that with segmental baffles in reducing pressure drop, eliminating dead zone and lowering the risks of vibration of tube bundle. This paper focused on the small-angle helical baffles that have been merely reported in open literature. These baffles are noncontinuous helical baffles with a helix angle of 10° to 30°, and their shapes are 1/4 ellipse, 1/4 sector and 1/3 sector. To assess the integrative performance, /? is employed, and the calculated results show that among the three baffle shapes the heat exchangers with a 1/4 sector helical baffle have the lowest pressure drop. At = 10° and 20°, 1/4 sector helical baffle heat exchangers show the best integrative performance; at = 30°, 1/4 ellipse and 1/4 sector helical baffle heat exchangers perform almost the same. For the study of helix angles, we found that 30° has the best integrative performance at low mass flow rate, almost the same as 20° at high mass flow rate.

关键词： heat transfer     pressure drop     helical baffle     CFD    

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Parametric analysis and design equation of ultimate capacity for unstiffened overlapped CHS K-joints

CHEN Yu, ZHAO Xianzhong, CHEN Yiyi

《结构与土木工程前沿（英文）》 2008年 第2卷 第2期   页码 107-115 doi: 10.1007/s11709-008-0014-x

摘要： A finite element model simulating an experiment on unstiffened, overlapped circular hollow structure (CHS) K-joints was generated and validated by comparing the ultimate capacities, deformation processes and failure modes of the experimental results. Using this model, the stress distribution, propagation of plasticity and the failure modes of overlapped joints with through-brace-in-compression and welded hidden seams were analyzed. The effect of geometric parameters, with or without hidden welds, and the loading hierarchy reversal of braces on the ultimate capacity of the joints were also studied. The results of finite element parametric analysis indicate that the brace-to-chord thickness ratio has relatively large effects on the failure mechanism and ultimate capacity of overlapped joints. It was also found that the absence of hidden welds has less significance on the ultimate capacity of through-brace-in-compression joints than through-brace-in tension joints. Finally, based on the design equation of gap joints, a formula predicting the ultimate capacity of overlapped CHS K-joints was derived by applying multivariate regression analysis. Results from the proposed design equation are consistent with experimental results.

关键词： regression analysis     consistent     unstiffened     plasticity     overlapped    

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Closed surface modeling with helical line measurement data

LI Ruqiong, LI Guangbu, WANG Yuhan

《机械工程前沿（英文）》 2007年 第2卷 第1期   页码 72-76 doi: 10.1007/s11465-007-0012-z

摘要： Models for surface modeling of free-form surface and massive data points are becoming an important feature in commercial computer aided design/computer-aided manufacturing software. However, there are many problems to be solved in this area, especially for closed free-form surface modeling. This article presents an effective method for cloud data closed surface modeling from asynchronous profile modeling measurement. It includes three steps: first, the cloud data are preprocessed for smoothing; second, a helical line is segmented to form triangle meshes; and third, Bezier surface patches are created over a triangle mesh and trimmed to shape on an entire surface. In the end, an illustrative example of shoe last surface modeling is given to show the availability of this method.

关键词： free-form surface     helical     triangle     design/computer-aided manufacturing     effective    

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Impacts of opening baffle of city road tunnels on natural ventilation performance

Weixiao YANG, Jincheng XING, Jianxing LI, Jihong LING, Haixian HAO, Zhiqiang YAN

《结构与土木工程前沿（英文）》 2013年 第7卷 第1期   页码 55-61 doi: 10.1007/s11709-013-0194-x

摘要： Based on the opening baffle mode for natural ventilation of city road tunnels, this paper studies the impacts of opening baffle on natural ventilation performance by verifying numerical simulation through model tests. By analyzing the impacts of installation angle, dimension, location, and quantity of opening baffle on ventilation performance, the paper reached the conclusions as follows: 1) When installation angle is larger than 45° and tunnel ventilation is well operated, the baffle exhaust could increase by at least 30% compared to when there is no baffle. 2) The baffle reaches its optimal performance when the length of the baffle is equal to the width of the city road tunnels. 3) Baffle exhaust could increase by 30% when it is installed in the downstream of openings. 4) The performance of a single baffle is better than that of multiple baffles.

关键词： city road tunnel     numerical simulation     baffle     top opening     natural ventilation    

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Performance of vertical axis water turbine with eye-shaped baffle for pico hydropower

Zhuohuan HU, Dongcheng WANG, Wei LU, Jian CHEN, Yuwen ZHANG

《能源前沿（英文）》 2022年 第16卷 第4期   页码 683-696 doi: 10.1007/s11708-020-0689-9

摘要： A series of inline pico hydropower systems, which could be used in confined space, especially for water distribution networks (WDNs), was designed and investigated. The turbine with an eye-shaped vertical water baffle was developed to evaluate the hydraulic performance. A three-dimensional dynamic mesh was employed and the inlet velocity was considered as the inlet boundary condition, whereas the outlet boundary was set as the outflow. Then, numerical simulations were conducted and the standard turbulence model was found to be the best capable of predicting flow features through the comparison with the experimental results. The effects of the opening diameter of the water baffle and installation angle of the rotor on the flow field in the turbine were investigated. The results suggested that the water baffle opening at = 30 mm and the rotor at a 52° angle could achieve the highest efficiency of 5.93%. The proper eye-shaped baffle not only accelerates the fluid flow and generates positive hydrodynamic torque, but also eliminates the flow separation. The scheme proposed in this paper can be exploited for practical applications in the water pipelines at various conditions and power requirements.

关键词： vertical axis water turbine     eye-shaped     vertical water baffle     pico hydropower    

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Convective heat transfer in helical coils for constant-property and variable-property flows with high

Yufei MAO, Liejin GUO, Bofeng BAI, Ximin ZHANG

《能源前沿（英文）》 2010年 第4卷 第4期   页码 546-552 doi: 10.1007/s11708-010-0116-8

摘要： Forced convection heat transfer of single-phase water in helical coils was experimentally studied. The testing section was constructed from a stainless steel round tube with an inner diameter of 10 mm, coil diameter of 300 mm, and pitch of 50 mm. The experiments were conducted over a wide Reynolds number range of 40000 to 500000. Both constant-property flows at normal pressure and variable-property flows at supercritical pressure were investigated. The contribution of secondary flow in the helical coil to heat transfer was gradually suppressed with increasing Reynolds number. Hence, heat transfer coefficients of the helical tube were close to those of the straight tube under the same flow conditions when the Reynolds number is large enough. Based on the experimental data, heat transfer correlations for both incompressible flows and supercritical fluid flows through helical coils were proposed.

关键词： convective heat transfer     helical coils     high Reynolds number     supercritical pressure     variable property    

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Cutting Force Model for a Small-diameter Helical Milling Cutter

LI Xiwen, YANG Shuzi, YANG Mingjin, XIE Shouyong

《机械工程前沿（英文）》 2007年 第2卷 第3期   页码 272-277 doi: 10.1007/s11465-007-0047-1

摘要： In the milling process, the major flank wear land area (two-dimensional measurement for the wear) of a small-diameter milling cutter, as wear standard, can reflect actual changes of the wear land of the cutter. By analyzing the wearing characteristics of the cutter, a cutting force model based on the major flank wear land area is established. Characteristic parameters such as pressure parameter and friction parameter are calculated by substituting tested data into their corresponding equations. The cutting force model for the helical milling cutter is validated by experiments. The computational and experimental results show that the cutting force model is almost consistent with the actual cutting conditions. Thus, the cutting force model established in the research can provide a theoretical foundation for monitoring the condition of a milling process that uses a small-diameter helical milling cutter.

关键词： computational     corresponding     helical milling     theoretical foundation     Characteristic    

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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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Geometric optimization model for the solar cavity receiver with helical pipe at different solar radiation

Chongzhe ZOU, Huayi FENG, Yanping ZHANG, Quentin FALCOZ, Cheng ZHANG, Wei GAO

《能源前沿（英文）》 2019年 第13卷 第2期   页码 284-295 doi: 10.1007/s11708-019-0613-3

摘要： In consideration of geometric parameters, several researches have already optimized the thermal efficiency of the cylindrical cavity receiver. However, most of the optimal results have been achieved at a fixed solar radiation. At different direct normal irradiance (DNI), any single optimal result may not be suitable enough for different regions over the world. This study constructed a 3-D numerical model of cylindrical cavity receiver with DNI variation. In the model of a cylindrical cavity receiver containing a helical pipe, the heat losses of the cavity and heat transfer of working medium were also taken into account. The simulation results show that for a particular DNI in the range of 400 W/m to 800 W/m , there exists a best design for achieving a highest thermal efficiency of the cavity receiver. Besides, for a receiver in constant geometric parameters, the total heat losses increases dramatically with the DNI increasing in that range, as well as the temperature of the working medium. The thermal efficiency presented a different variation tendency with the heat losses, which is 2.45% as a minimum decline. In summary, this paper proposed an optimization method in the form of a bunch of fitting curves which could be applied to receiver design in different DNI regions, with comparatively appropriate thermal performances.

关键词： cylindrical cavity receiver     3-D numerical simulation     geometric optimization     direct normal irradiation    

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Simultaneous acquisition of CT angiography and whole brain CT perfusion images by using multiphase dynamic helical

Weiwei CHEN, Jianpin QI, Wenzhen ZHU, Wenhua HUANG, Jinmei SONG

《医学前沿（英文）》 2009年 第3卷 第2期   页码 230-235 doi: 10.1007/s11684-009-0023-8

摘要： We implemented a new protocol — multiphase dynamic helical scan to acquire CT angiography (CTA) and whole brain CT perfusion (CTP) images simultaneously with single scan on 16 multidetector CT (MDCT). A total of 90 patients who were randomly assigned into 3 groups were included in our study. Each group underwent CT scan by using the new protocol, traditional CTA and CTP protocol, respectively. The image quality of CTA, the CTP parameter values and the X-ray doses were measured and compared between the new protocol and the traditional protocols. There was no statistically significant difference in the CTA image quality between the above methods ( =0.55). For CTP parameters, the new protocol tended to overestimate the blood volume (BV) and blood flow (BF) value, and to underestimate the mean transit time (MTT) value compared with the traditional method. However, there was no statistically significant difference in BV, BF, and MTT value between the two methods except permeability surface (PS) ( >0.05). The volume CT dose index (CTDIvol) and dose length product (DLP) of our protocol were lower than the traditional one. The new protocol can obtain valuable diagnostic information in a shorter time without significant compromise in image quality. In addition, it reduces the radiation dose as well as contrast medium usage on the patient.

关键词： computed tomography angiography     computed tomography perfusion    

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Gene delivery into isolated

Nan Zheng, Ziyuan Song, Yang Liu, Lichen Yin, Jianjun Cheng

《化学科学与工程前沿（英文）》 2017年 第11卷 第4期   页码 521-528 doi: 10.1007/s11705-017-1612-8

摘要： The application of gene delivery materials has been mainly focused on mammalian cells while rarely extended to plant engineering. Cationic polymers and lipids have been widely utilized to efficiently deliver DNA and siRNA into mammalian cells. However, their application in plant cells is limited due to the different membrane structures and the presence of plant cell walls. In this study, we developed the cationic, -helical polypeptide that can effectively deliver DNA into both isolated protoplasts and intact leaves. The PPABLG was able to condense DNA to form nanocomplexes, and they exhibited significantly improved transfection efficiencies compared with commercial transfection reagent Lipofectamine 2000 and classical cell penetrating peptides such as poly(L-lysine), HIV-TAT, arginine9, and poly(L-arginine). This study therefore widens the utilities of helical polypeptide as a unique category of gene delivery materials, and may find their promising applications toward plant gene delivery.

关键词： α-helical polypeptide     plant gene delivery     protoplast     intact leaves     transfection    

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磁控螺旋形微纳米机器人在生物医学方面的应用 Review

邱发敏, Bradley J. Nelson

《工程（英文）》 2015年 第1卷 第1期   页码 21-26 doi: 10.15302/J-ENG-2015005

摘要：

磁控螺旋形微纳米机器人可在低强度旋转磁场（<10 mT）的驱动下，实现亚微米精度的三维（3D）游动。由于低强度磁场对细胞和组织无害，磁控螺旋形微纳米机器人在生物医学方面有很大的应用前景，如微创手术、细胞操作和分析以及靶向治疗。本文系统介绍了磁控螺旋形微纳米机器人的制造方法、运动控制和生物医学应用。

关键词： 磁控螺旋形微纳米机器人     可游动微纳米机器人     人造细菌鞭毛（ABFs）     功能化     生物医学应用    

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Application of different CFD multiphase models to investigate effects of baffles and nanoparticles on heat transfer enhancement

Ali SHAHMOHAMMADI,Arezou JAFARI

《化学科学与工程前沿（英文）》 2014年 第8卷 第3期   页码 320-329 doi: 10.1007/s11705-014-1437-7

摘要： In this work, the effect of baffles in a pipe on heat transfer enhancement was studied using computational fluid dynamics (CFD) in the presence of Al O nanoparticles which are dispersed into water. Fluid flow through the horizontal tube with uniform heat flux was simulated numerically and three dimensional governing partial differential equations were solved. To find an accurate model for CFD simulations, the results obtained by the single phase were compared with those obtained by three different multiphase models including Eulerian, mixture and volume of fluid (VOF) at Reynolds numbers in range of 600 to 3000, and two different nanoparticle concentrations (1% and 1.6%). It was found that multiphase models could better predict the heat transfer in nanofluids. The effect of baffles on heat transfer of nanofluid flow was also investigated through a baffled geometry. The numerical results show that at Reynolds numbers in the range of 600 to 2100, the heat transfer of nanofluid flowing in the geometry without baffle is greater than that of water flowing through a tube with baffle, whereas the difference between these effects (nanofluid and baffle) decreases with increasing the Reynolds number. At higher Reynolds numbers (2100–3000) the baffle has a greater effect on heat transfer enhancement than the nanofluid.

关键词： CFD simulation     heat transfer     nanofluid     baffle     single phase model     multiphase model    

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Effects of baffles on separation of aqueous ethanol solution with hollow fibers

Zhihong YANG, Guoliang ZHANG, Lan LIN, Danping REN, Qin MENG, Hongzi ZHANG

《化学科学与工程前沿（英文）》 2009年 第3卷 第1期   页码 68-72 doi: 10.1007/s11705-009-0130-8

摘要： The effects of baffles on the operation and mass-transfer characteristics in novel hollow fiber membrane contactor used in distillation were investigated. Hollow fiber membranes, coated with a 7 μm polydimethyl-siloxane, were operated as structural packing in the separation of ethanol-water solutions. The parallel flow mode was chosen for separation due to the stronger driving force of the concentration difference, in which liquid flows through the lumens of the fibers and vapor flows countercurrent-wise outside the fibers. Two baffles were installed on the shell side of the membrane contactors to enhance separation, which had a round shape with a semi-lunar hole. The results show that both baffled and unbaffled membrane contactors gave better, more productive separations than traditional packing in distillation, such as the excellent Sulzer Gauze BX structured packing. The baffled membrane contactors performed better than unbaffled ones, especially at high vapor velocities. The minimal HTU of membrane contactor with baffles could reach as low as 4.5 cm, and almost all the contactors could work well above the limit where flooding normally occurs in conventional cases. Theoretical analysis predicted that baffles helped membrane module to obtain a higher mass-transfer coefficient and a smaller mass-transfer resistance. Finally, theoretical mass-transfer coefficient and experimental value were compared as well as the contribution of each individual mass-transfer coefficients among liquid, gas and membrane.

关键词： hollow fiber     membrane contactor     baffle     mass-transfer     ethanol-water    

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标题 作者 时间 类型 操作

Characteristics of flow and heat transfer of shell-and-tube heat exchangers with overlapped helical baffles

Tingting DU, Wenjing DU

期刊论文

CFD simulation on shell-and-tube heat exchangers with small-angle helical baffles

Minhua ZHANG,Fang MENG,Zhongfeng GENG

期刊论文

Parametric analysis and design equation of ultimate capacity for unstiffened overlapped CHS K-joints

CHEN Yu, ZHAO Xianzhong, CHEN Yiyi

期刊论文

Closed surface modeling with helical line measurement data

LI Ruqiong, LI Guangbu, WANG Yuhan

期刊论文

Impacts of opening baffle of city road tunnels on natural ventilation performance

Weixiao YANG, Jincheng XING, Jianxing LI, Jihong LING, Haixian HAO, Zhiqiang YAN

期刊论文

Performance of vertical axis water turbine with eye-shaped baffle for pico hydropower

Zhuohuan HU, Dongcheng WANG, Wei LU, Jian CHEN, Yuwen ZHANG

期刊论文

Convective heat transfer in helical coils for constant-property and variable-property flows with high

Yufei MAO, Liejin GUO, Bofeng BAI, Ximin ZHANG

期刊论文

Cutting Force Model for a Small-diameter Helical Milling Cutter

LI Xiwen, YANG Shuzi, YANG Mingjin, XIE Shouyong

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

Geometric optimization model for the solar cavity receiver with helical pipe at different solar radiation

Chongzhe ZOU, Huayi FENG, Yanping ZHANG, Quentin FALCOZ, Cheng ZHANG, Wei GAO

期刊论文

Simultaneous acquisition of CT angiography and whole brain CT perfusion images by using multiphase dynamic helical

Weiwei CHEN, Jianpin QI, Wenzhen ZHU, Wenhua HUANG, Jinmei SONG

期刊论文

Gene delivery into isolated

Nan Zheng, Ziyuan Song, Yang Liu, Lichen Yin, Jianjun Cheng

期刊论文

磁控螺旋形微纳米机器人在生物医学方面的应用

邱发敏, Bradley J. Nelson

期刊论文

Application of different CFD multiphase models to investigate effects of baffles and nanoparticles on heat transfer enhancement

Ali SHAHMOHAMMADI,Arezou JAFARI

期刊论文

Effects of baffles on separation of aqueous ethanol solution with hollow fibers

Zhihong YANG, Guoliang ZHANG, Lan LIN, Danping REN, Qin MENG, Hongzi ZHANG

期刊论文