横掠螺旋翅片管管束对流换热的试验研究

本文在考虑影响气体横掠螺旋翅片管管束的对流换热的诸因素的基础上,使用两相闭式热虹管为传热元件,根据等雷诺数法的原则,通过试验及数据处理,对传热特性和阻力特性进行了分析和研究,并提出相应的数学准则式,这些公式可为设计提供依据。     

多孔结构及表面浸润性对池沸腾传热影响的研究进展

沸腾传热是一种高效换热方式,在多种领域具有广泛应用前景。其中多孔金属表面由于其比表面积大、导热性能好以及汽化核心密度高等突出优点,受到广泛关注;而多孔表面、耦合表面、亲疏水改性能极大地提高临界热流密度,调控沸腾传热,变无序为可控,正迅速成为强化沸腾相变传热领域的新热点。本文追踪了多孔表面和表面改性强化沸腾传热的最新进展,重点介绍多孔尺度、形状、核化点布局及整体/局部亲疏水性强化沸腾性能及机理;简要分析了以Zuber临界热流密度公式为基础的Kandlikar系列公式;整理近年来不断完善和改进的沸腾传热机理模型,认为微液层蒸发和瞬态热传导是微纳多孔表面强化沸腾的主导机制;进一步指出微纳多孔表面耦合、局部亲疏水性处理是强化沸腾传热新的发展方向。     

多层流态化床的研究Ⅱ 气-固系

本文研究了气-固系多层流态化床（溢流管式,“B”型）中溢流管的工作性能及传热计算方法。提出了初步的关联影响溢流管固体流率的各因素的方法。在传热部分,作者根据流化床中气- 固相温度接近相等的特点,运用气-液系统中平衡级的概念导出多层流态化床传热计算的公式。     

热管技术原理及其在热流道模具中的应用

概述热管的结构及其利用工作液相变时潜热交换作用的传热机理,比较了运用热管技术与常用电阻加热器传热的优缺点,并介绍热管技术在热流道系统中应用的进展。热管技术与热流道系统相结合。能满足热流道加热元件对均温性及易于控温的要求,可以极大地促进热流道技术的使用和推广。     

螺旋扭扁管强化传热与阻力性能的模拟分析

运用数值模拟的方法对螺旋扭扁管的传热与阻力性能进行了分析与研究,并与普通椭圆直管相比较,研究了管内流体的Re、Pr以及管子几何尺寸对其管内传热与流动性能的影响。结果表明,螺旋扭扁管是一种较好的强化传热元件,尤其对具有高Pr数的大粘度流体在低Re数的层流或过渡流时具有较好的强化传热效果。根据数值模拟的结果,利用多元线性回归的方法给出了努塞尔数Nu和阻力系数f的准则公式。     

缠绕管式换热器管程的非平衡热力学研究

以描述缠绕管式换热器管程对流传热的Schmidt公式为基础,将内部流动传热的非平衡热力学模型相与Schmidt公式相结合,对缠绕管式换热器管程对流传热的非平衡热力学理论模型进行了理论研究;提出了传热熵产数(Ns,HX)和阻力熵产数(Ns,P)的概念;对缠绕管式换热器管程的Nu、ΔP、Ns,HX和Ns,P的变化规律进行了研究;结果显示,Nu随着Re的升高而升高,传热熵产数(Ns,HX)随着Re的升高而降低;ΔP和阻力熵产数(Ns,P)都随着Re的升高而增大;传热熵产数(Ns,HX)和阻力熵产数(Ns,P)能有效反映缠绕管式换热器管程对流传热过程的不可逆损失的变化规律,揭示了缠绕管式换热器管程对流传热的非平衡热力学原理。     

用异种气体射流冲击浸没溶液中微小加热壁面的传热传质过程

本文研究了异种气体喷射冷却浸没液体中微小发热元件的传热特性,以及液体和壁面之间的传热与吹气速率、喷嘴到加热表面的距离、液相温度、热流率、溶液物性等等之间的关系。用异种气体冲击浸没R-113或乙醇中的加热壁面,其传热显著增加,在热流率不很高或液相温度较高时,加热壁面的温度可低于冷却介质的温度,实验结果表明,液体和壁面之间的传热不仅随气泡对液体的扰动而增加,而且随壁面附近液相向气相蒸发传质而增加。本文分析了其传热机理,提出了一种同时传热传质的模型解释这种系统中特殊的传热特性,用实验数据对对流传热系数h_(?)以及传质引起的传热进行了关联。     

池式核沸腾中的“界面汽化热阱”效应

采用扩散极限电流技术 ( LDCT)与传热测定同时进行的实验方法分析了池核沸腾中的“界面汽化热阱”效应。传热实验所测定的是池核沸腾的总换热系数 ,由 LDCT测定并以类比原理可以获得对流传热系数 ,两者差值即为“界面汽化热阱”效应。实验结果表明 ,沸腾时 ,“界面汽化热阱”效应随热流率的提高而显著增大。对以 LDCT法测得的对流传热数据进行关联 ,获得了准数式。     

不同结构换热管管内传热及流动阻力性能的试验研究

本文研究了圆形光管、圆形内肋管、椭圆管及滴形管的管内传热及流动阻力性能，整理出了相应的传热及流动阻力关联式，并对其进行了比较分析。     

不同结构换管管内传热及流动阻力性能的试验研究

本文研究了圆形光管、圆形内肋管、椭圆管及滴形管的管内传热及流动阻力性能，整理出了相应的传热及流动阻力关联式，并对其进行了比较分析。     

The heat and mass transfer from a fluid sphere at large reynolds and peclet number

Analytic expressions have been derived for the steady rate of heat or mass transfer from a fluid sphere in uniform motion at large Reynolds and Peclet number. The solution is applicable to cases where both phase resistances are of the same order of magnitude, or when the resistance of one phase is negligible. The analysis has shown that if finite values of fluid viscosity and density are considered the transfer rates are considerably less than those obtained from the ideal fluid model. The maximum flux for a fluid sphere occurs near the equatorial plane and in this respect its behavior differs significantly from a solid sphere.     

Thermal Blending Time Associated With a Charge of Hot Particles Added to a Fluidized Bed of Uniform Temperature

The process of heat transfer between particles in a fluidized bed is important for many industrial fluidized bed processes. The problem associated with studying this phenomenon is the confounding effect of particle mixing on heat transfer. The work described here was undertaken to describe the process in which heat is added to a fluid bed process by adding a hot charge of particles to a colder fluidized bed. The rate of heat transfer in this instance can have a significant impact on performance of the fluid bed process, depending upon its application. Both the method of analysis and the results of the work are applicable to other fluidized bed processes, particularly those associated with the thermal upgrading of heavy oil. The method of data analysis, based on binomial statistics, allowed useful data to be extracted from a complex system without the need for a large number of experiments. The analysis also allowed for some assessment of the relative importance of mixing and heat transfer, which has not been possible with other approaches. The results of the experiments were further explored using a bubbling bed model that incorporated both heat transfer and solids mixing. This allowed for the formation of a conceptual model, validated by the experimentation, that explains the relative functions of the two transfer processes in the dispersion of heat from a hot charge of particles to the bulk of a fluidized bed.     

R22在水平双侧强化管外池沸腾换热

对2根双侧高效强化管(管I,管II)在饱和温度为9.6℃和5.8℃工况下进行了水平管外R22池沸腾换热实验研究,采用Wilson热阻分离法得到制冷剂侧沸腾换热表面传热系数,并对实验结果进行了热阻分析。实验结果表明:在同样条件下,2根强化管的管内对流换热表面传热系数是光管的2.2—2.8倍。在饱和温度为9.6℃时,管II的管外沸腾换热表面传热系数达到(2.2—3.4)×104W/(m2.K),高出光管一个量级。随后进行的热阻分析工作,有利于强化换热管的进一步开发。热阻分析表明:在实验范围内,管内外两侧的热阻基本相当,随着管内水流速的增加,管内水侧热阻所占比例降低,管外制冷剂侧热阻所占比例增大。对于沸腾高效强化管的开发,两侧的强化都是应该关注的。     

R123在水平双侧强化管外池沸腾换热

对3根双侧高效强化管（管Ⅰ为Turbo-B型管,管Ⅱ、管Ⅲ为改进的Turbo-B型管）在饱和温度为12℃和10℃工况下进行了水平管外R123池沸腾换热的实验研究,采用Wilsan热阻分离法得到制冷剂侧沸腾换热表面传热系数,并对实验结果进行了热阻分析.实验结果表明：在同样条件下,3根强化管的管内对流换热表面传热系数是光管的2.8～3.1倍.在同样的热通量范围内,对于Turbo-B型管,R22池沸腾换热性能的强化效果比R123更明显.随后进行的热阻分析工作,有利于强化换热管的进一步开发.热阻分析表明：在实验范围内,管内外两侧的热阻基本相当,随着管内水流速的增加,管内水侧热阻所占比例降低,管外制冷剂侧热阻所占比例增大.对于沸腾高效强化管的开发,两侧的强化都是应该关注的.     

Thermal dispersion and wall heat transfer in packed beds

A new analysis showing the effect of axial and radial thermal dispersion and wall thermal resistance upon heat transfer to fixed beds of solids is presented. By application of this theory and non-linear regression, coefficients of axial and radial dispersion and wall heat transfer coefficients are calculated from experimental measurements of radial temperature profiles in fixed beds heated at the wall.The experiments have been performed for beds packed with glass and with metallic particles within the particle Reynolds number range from 1 to 400.The calculated coefficients are compared with experimental values reported by other workers. Some differences are attributed to the neglect of axial dispersion in the work of others, but other differences are significant in that, for example, thermal characteristics of fixed beds of metallic particles differ from those of non-metallic particles.     

基于颗粒尺度的离散颗粒传热模型

颗粒间传热在诸多工业过程中有着十分重要的作用。详细考虑颗粒间传热机理,对颗粒间各传热途径建模,包括颗粒内部导热、颗粒粗糙表面传热、颗粒表面气膜及接触颗粒间隙气膜传热,并与离散颗粒模型(DEM)耦合,建立颗粒尺度下离散颗粒传热模型。以固定床为对象,考察颗粒粒径、颗粒比热容、颗粒热导率及压缩负载对固定床有效传热系数的影响,并将本文计算值和文献的实验值及模型预测值对比,结果表明,该模型可定量预测固定床有效传热系数。本文建立的离散颗粒传热模型为合理预测颗粒体系内的传热提供了一种有效方法。     

分流式换热器的性能比较和理论分析

基于对<2-4>及<2-6>型分流式换热器基本方程的解析解,给出了温度效率P和对数平均温差修正系数F的计算公式。在热容量比R及传热单元教NTU的实际有意义的范围内,比较了<1-n>(n=2,3,4)及<2-n>(n=4,6,8)型分流式换热器的P值。对结果进行了有益的讨论。     

疏水表面结霜初期液滴生长的理论分析

研究了自然对流条件下疏水表面结霜初期冷凝液滴的生长过程, 建立了考虑不凝气影响的液滴传热及生长模型, 分析了表面接触角和冷面温度对液滴生长的影响。结果表明, 液滴生长过程中的主要热阻为液滴内部导热热阻和相界面热阻, 随着表面接触角的增大, 这两个主要热阻均增大, 因此表面疏水性越好, 液滴生长越缓慢;而由于冷凝传热温差随冷面温度降低而增大, 因此冷面温度越低, 液滴生长越快。     

超临界压力下航空煤油传热恶化的分析与预测

对竖直上升圆管内超临界压力航空煤油的传热恶化进行了实验研究。考察了浮升力和热加速对换热的影响机制,通过判别准则的适用性分析,选取能较好描述传热恶化的因子组,修正得到了合理的临界值,从而获得了适用于航空煤油的判别准则。基于可控参数建立了传热恶化临界热通量预测公式。阐述了传热恶化引发热声流动不稳定的过程。通过浮升力因子和热加速因子修正建立了换热关联式。结果表明：浮升力因子Bu和热加速因子Ac分别高于1.57×10^-5和4.92×10^-6时,两者将削弱边界层内剪切力,引发传热恶化现象。拟沸腾也是传热恶化和热声流动不稳定的诱因。     

On the heat transfer mechanism in three phase fluidized beds

A two resistance model is proposed for the heat transfer between a coaxially mounted heater and a three phase fluidized bed. Effects of gas and liquid velocity and particle size on individual heat transfer resistances in the heater and in the fluidized bulk zones have been determined. The optimum bed porosity at which the maximum heat transfer coefficient occurred coincided with the bed porosity at which the boundary layer thickness around the heater attained a minimum value. The fluidized bed resistance attained its minimum value when the maximum heat transfer coefficient is achieved in two and three phase fluidized beds. The heat transfer in the zone adjacent to the healer is found to be the rate controlling step since the contribution of fluidized bed resistance was found to be less than 10% of the heater zone resistance in two and three phase fluidized beds. The heat transfer resistances in liquid and three-phase fluidized beds have been represented by a modified Stanton and Peclet numbers based on the heat transfer resistances in the heater zone and in the fluidized bulk zone in series.