粗糙矩形通道的强化换热与流动阻力

本文研究了粗糙矩形通道的强化换热和流动阻力,给出了通道中壁和角区局部换热系数经验公式与流动阻力计算式;得出了在一定的h/de情况下s/h的最佳强化换热区域。实验结果表明在相同的h/de和s/h情况下,横肋管的换热性能优于斜肋管。     

内插直线型转子的管内流动与换热实验研究

实验研究了内插不同结构参数直线型转子的管内流动阻力和传热特性,结果表明,由于中空的结构形式,直线型转子可增大壁面处流体速度梯度,增强扰动,从而在阻力增加不大的条件下,实现强化换热和除垢抑垢。减小螺旋叶片角度、优化直线段形状、设置凸起等方式有助于提高内插转子的管内综合换热性能,三正三反交替布置为较优的转子排列方式。     

螺旋升角对凝结换热特性影响的研究

本文对具有不同螺旋升角的螺旋槽换热管进行了凝结换热和阻力特性试验.试验结果表明,螺旋升角在螺旋槽管凝结换热过程中具有不可忽视的影响.分析了螺旋升角β对凝结换热及阻力特性的影响机理,提出考虑了螺旋升角因素的凝结换热经验关联式.     

内置弹簧线圈平板通道流动传热实验研究

提出了在平行平板通道中等间隔布置轴线垂直于流动方向的弹簧线圈以强化传热的方法,并对其换热和流动阻力特性进行了实验研究。实验分别对水-水换热和水-油换热进行了测试,得到了所测参数范围内水侧和油侧的换热及阻力关联式。通过与典型人字形板式换热器实验结果的对比,分析了弹簧线圈对不同黏性流体流动换热的影响,得出平板间填充弹簧线圈的结构更适用于高黏性流体的流动换热。     

小管径三排管开缝翅片传热特性的实验与数值研究

本文对应用于二氧化碳跨临界空调制冷循环的三排管小管径开缝翅片管换热器空气侧的传热及阻力性能进行了实验与数值研究,数值模拟结果与实验值的最大偏差仅为10%.此外,通过四种途径研究了倾角对换热的影响,发现倾角有利于换热强化但换热量的增加不及压降的增加.     

波纹内翅片管中对流换热与阻力特性的实验研究

本文研究了空气在一种波纹内翅片管内强制对流的换热与阻力特性,得出了所测参数范围内换热Nusselt数和阻力系数f随Reynolds数变化的实验关联式,并与类似波纹内翅片管的换热效果进行了比较,结果表明波纹内翅片管换热强化的程度与其结构有很大的关系。     

管排数对翅片管蒸发器换热性能影响的仿真计算

通过对翅片管蒸发器建立集中参数模型,研究了管排数对变频空调蒸发器换热性能的影响。研究结果表明,管排数增加,总换热量的增加并不显著,但管排数每增加一排平均每排管的换热量减少18%左右;风机功率越大,达到最大换热量的管排数也越多。     

波纹板式空冷器阻力与传热特性实验研究

在可改变风量和热水流量的实验条件下,对波纹板式空冷器的阻力与传热特性进行实验研究。得到了空气侧的阻力降关联式以及两侧的对流换热系数关联式,其适用于热水雷诺数在2000-8000之间、空气雷诺数在2000-10000之间。在相同工况下,比较了波纹板式、光管式和翅片管式空冷器的性能指标,结果表明:迎面风速在2.45-4.1 m/s之间,波纹板式空冷器传热系数达到100-160 W/m2/℃;约比光管式提高70%,但只有以管束外表面为基准的翅片管式传热系数的六分之一;板式空冷器单位体积换热量约是翅片管式空冷器的1.5倍,是光管式的15倍;板式空冷器单位功耗换热量约是光管式空冷器的5.5倍,而翅片管式空冷器与光管式空冷器则相差不大。     

带重复肋粗糙同心管湍流换热与流阻

本文对空气流过内管具有梯形重复肋的同心管湍流换热和流阻进行了实验研究,肋的相对间距s/h变化范围为8—17,雷诺数Re的范围为1×10~4—1.5×10~5,得到这种肋对于换热及流阻影响的规律,与光滑同心管实验进行了比较,换热系数为光滑管的1.5—2.1倍,对其热性能进行了分析.     

波纹内翅片管换热与阻力特性的实验研究

本文研究了三组内翅片管的湍流流动与换热特性,拟合出所测参数范围内阻力和换热的实验关联式,并运用相同质量流量、相同泵功率、相同压降三种准则比较了不同组翅片管之间的强化传热效果。     

三维内肋管内流态的划分及过渡流判据的实验研究

1前言三维内肋管（见图1）已在许多文献中进行了研究[1～7]。其中文献[7]首次提出了三维内肋管的流态划分问题，指出应按人工粗糙管的流态模式合理地划分为层流区、临界区、过渡流区和旺盛湍流区，且其相邻两区的转换雷诺数都应与肋的几何结构有关。文献[7]主要研究了该管达旺盛湍流时的雷诺判据。本文将着重研究该管达过渡流的雷诺判据。2实验装置与实验方法实验装置如图2所示。实验管几何结构见表1。1．鼓风机2．滤网3LWQ－15型气体涡轮流量变送器（或LZJ－15型玻璃转子流量计）4．XSF－40流量指示积算仪5．调压变压器6．直管段7．UJ…     

Investigation of Thermal Performance of Perforated Finned Heat Exchangers

In this study, the thermal performance of perforated finned heat exchangers with angle of rotation θ was experimentally investigated. Six-millimeter-diameter holes that were opened on each circular fin on a heating tube have a potential to reduce the thickness of the boundary layer that is formed on the circular fins placed on the heating tube, thus increasing heat transfer through convection in this area. The experiments were carried out at six different angular locations to determine the best angular location. In addition, a perforated finned heater was compared with an imperforate finned heater. For the finned heater at 60°, the effectiveness is 18% higher and the pressure drop is 1.16% lower than other angular positions. In this respect, it can be concluded that the best angular position is 60°. In addition, results show an increase in effectiveness with an increasing number of transfer units.     

The Efficiency Analysis of a Finned Cross-flow Heat Recovery Unit

A finned convergent-divergent plate-type cross-flow heat recovery unit is manufactured and tested for efficiency analysis. Temperature and pressure drop experiments are conducted with various working conditions of the boiler, fan, preheater, and reheater of the system. Variation of Nusselt number and friction factor with Reynolds number is analyzed. Variation of effectiveness and exergy loss with number of transfer units is calculated and discussed in terms of extant literature. Experimental results indicate that the most important parameter affecting the heat transfer is winglet geometry and fluid velocity. The efficiency can be improved successfully by controlling these parameters for thermal applications.     

EFFECTS OF THE PITCH OF IN-LINE DELTA WINGLET VORTEX GENERATORS ON HEAT TRANSFER OF A FINNED THREE-ROW FLAT TUBE BANK

The naphthalene sublimation technique via the heat and mass transfer analogy is used to study the effects of the pitch of in-line delta winglet vortex generators on heat transfer and pressure drop of a finned three-row flat tube bank. The results show that the pitch of the in-line vortex generator has a strong effect on the heat transfer performance. The optimal pitch depends on the performance evaluation criteria. With the configurations considered in this article, for identical pumping power or combined constraint, a small pitch of 0.33 is best; for the identical pressure drop constraint, a value of 0.42 is best.     

翅片管束式管壳式换热器三维数值模拟研究

本文提出了运用多孔介质模型、分布阻力模型和k-ε湍流模型对壳侧为翅片管束的壳管式换热器壳侧速度场与温度场进行三维数值模拟的方法,并对一相应类型换热器壳侧的流动与换热进行了数值模拟,得出了壳侧流场参数的图示以及壳侧进出口压降,温差,换热量随壳侧Re变化的特性曲线。     

鳍片管束撞击式气固分离器的试验研究

本文提出了一种应用于循环流化床，兼有强化传热的鳍片管束惯性分离器。试验表明此分离器具有高效、低阻、结构紧凑等优点，特别是它能强化换热，同时在管内工质冷却下鳍片能保持较低温度，因而能使用普通锅炉用钢。本文通过试验研究了这一分离器的流动结构、分离性能及有关设计参数的选择。     

一种内螺纹强化管的冷凝实验研究

实验研究了环保替代制冷工质R410A、R22在水平强化管内冷凝换热特性,探索了热流密度、水流速度对换热特性、压降的影响。实验测试管为内螺纹强化管,长度为5.2 m,外径为9.52 mm。实验结果表明:制冷剂R410A、R22的传热系数和压降随热流密度的增大而增大,同时内螺纹管的换热系数还随管外冷却水流量的增加而升高,压降随冷凝温度的升高而降低,而R410A比R22有更好的换热效率和较小的压降。     

Comprehensive Study of the Effect of the Addition of Four Drag Reducing Macromolecules on the Pressure Drop and Heat Transfer Performance of Water in a Finned Tube Heat Exchanger

Abstract

In the present study the effects of the addition of four drag reducing agents (DRA), including carboxy methyl cellulose with high molecular weight (DRA1) and medium molecular weight (DRA2), polyacrylamide (DRA3) and the natural polymer, xanthan gum (DRA4), to water on the pressure drop and heat transfer performance in a finned tube-heat exchanger were compared. Laminar flow (Reynolds number (Re) <1400) was studied to transfer heat between water and air in the finned tube heat exchanger. The results showed that DRA1, with a maximum %DR of 26%, and DRA4, with a maximum %DR of 5%, were the highest and the lowest obtained results, respectively. In the case of heat transfer reduction percentage (%HTR), DRA4, having more than 34.5%, was the highest, and DRA1, with about 13.7%, was the lowest result for the concentration range of 0-100?ppm and temperature range of 40–65?°C.     

厚翅片管内流体流动和传热的数值分析

本文应用Ｐａｔａｎｋａｒ等人［１］研究薄翅片管的湍流模型，对一种工业化的厚翅片管内的流体流动和传热进行了数值分析。计算范围包括了层流和湍流（Ｒｅ＝１０１～１０６），所得计算结果与较窄范围内实验所测的传热与阻力数据相当符合，本计算结果具有较大的推广价值。     

超临界LNG在错列S形翅片微通道的流动传热特性研究

作为一种新型微通道换热器,印刷电路板式换热器(Printed Circuit Heat Exchanger, PCHE)因比表面积大、耐高压和低温、海上适应性强以及便于模块化等特点,近年来逐渐成为浮式LNG接收站和浮式储存及再气化装置的主低温换热器首选。针对改进后的错列S型翅片,对超临界LNG在翅片通道内的流动传热特性展开数值模拟,并重点探析拟临界工况附近的对流换热特征。结果表明,错列S形翅片能在保证良好的传热性能下获得较低的阻力压降;在LNG-丙烷中间介质气化器内,随着超临界LNG压力的升高,能带来更高的出口温度,沿流通长度方向上定压比热的变化也趋于平缓,而变化过渡区也会逐渐趋于温度更高的流场区,同时定压比热变化的极大值也会大幅缩小;入口段的温度场变化梯度明显,且变化梯度会随着压力提高而进一步增大;在靠近拟临界压力处,超临界LNG在翅片流道中会由于物性剧烈变化而出现传热异常行为。