The Effect of Wave Formation and Wetting Angle on the Thermocapillary Breakdown of a Falling Liquid Film

An experimental investigation is performed of the breakdown of a liquid film flowing down a vertical plate with a heater sized 150×150 mm. The main parameters which are varied in the experiment are the Reynolds number Re = 0.47 to 331 and the heat flux q = 0 to 1.92 W/cm². It is found that the effect of the heat flux on the wave motion of the liquid film causes the formation of a jet flow. Dry spots are formed in the region of thin film between the jets. For the purpose of investigating the effect of wave formation on the film breakdown, the distance between the nozzle and heater is varied from 41.5 to 200 mm. It is found that the distance between the nozzle and heater defines the hydrodynamics of the liquid at relatively low heat fluxes, but has no appreciable effect on the heat flux at which the film breakdown occurs. Different working liquids and coatings of the working surface are used in the experiments to investigate the effect of the wetting angle on the film breakdown. The equilibrium wetting angle is measured by the "bubble" method. No effect of the equilibrium wetting angle on the nonisothermal breakdown of the film was revealed.     

Heat Transfer from a Local Heat Source to Subcooled Liquid Film

An experimental investigation is performed of heat transfer from a local heat source to films of water and low-boiling dielectric liquid that flow down a vertical plate by gravity. The liquids are substantially subcooled. In the case of perfluorotriethylamine flow, regular structures are formed in the film at the threshold value of the heat flux density. After the heated layer of liquid comes to the film surface, three characteristic modes of heat transfer are observed, which are associated with the variation of the modes of liquid flow caused by thermocapillary convection. At low values of the Reynolds number of the film, a specific form of critical heat transfer is observed, which is characterized by disintegration of the jet into droplets and their separation from the heater.     

热转印膜用离型剂的制备与性能研究

通过对纳米SiO2先进行预处理改善分散性,再加入成膜物质和表面活性剂制得的离型剂,其固化性、稳定性较好,涂布于PET基材薄膜上,测得单位面积油墨残留率小,说明该乳液起到离型作用.     

土壤源热泵地下垂直埋管换热器常用传热模型的研究

本文介绍了土壤源热泵的国内外研究现状以及三种常用的埋管换热器传热模型,分析了这三种模型各自具有的特点和适用条件.并对传热模型的选取提出了自己的观点,为特定条件下如何选取合适的模型提供了一定参考.     

Heat Transfer Enhancement in a Heated Liquid Film under the Action of External Artificial Perturbations

Heat transfer in a heated film of distilled water under the action of external artificial perturbations with “the most dangerous wavelength” and variation in the Reynolds number from 300 to 500 has been studied. It has been shown that the action of artificial perturbations with an increase in the heat flux density leads to a change in the rivulet-wave structure of the flow, increase in wave amplitudes, and, finally, heat transfer enhancement.     

壳聚糖涂膜材料的传热特性研究

采用XRD,TG,DSC表征了壳聚糖的分子结构(包括脱乙酰度、结晶度、玻璃化温度),测定了壳聚糖涂膜液的特性粘度,研究了壳聚糖的结构和使用条件(时间、温度)对壳聚糖涂膜传热特性的影响规律.结果表明:壳聚糖的玻璃化转变温度随其结晶度的增大而升高;脱乙酰度越大、特性粘度越小、玻璃化温度越低,涂膜的热传递速率越快;壳聚糖涂膜的贮藏时间越长,其热传递速率越慢.     

地源热泵地埋管单位埋管深度换热量指标的推导

根据规范中有关公式,代入相关参数进行详细推导计算,得出各部分热阻,进而计算出各类典型岩土的单位埋管深度换热量指标;并利用GLD地埋软件验算,结论相符,可简便应用于实际工程设计。     

传热规律对内可逆四热源吸收式热泵循环性能的影响

建立了传热规律为Q∝△(T^n)时内可逆四热源吸收式热泵循环模型,导出了循环泵热率和泵热系数的一般关系;并导出了传热服从线性唯象定律时的基本优化关系、循环中工质的最佳工作温度和换热器传热面积的最佳分配关系;通过数值算例分析了传热规律对循环性能的影响规律,比较了传热面积最优分配前后循环的最优性能。     

重力供液系统中过热度对传热面积影响的研究

本文主要对重力供液系统中蒸发器出口制冷剂的过热度进行分析,通过visual basic软件仿真计算出全部用气化潜热制冷需要的蒸发器面积A1,和有过热度后多出来的面积A2。将A1＋A2与蒸发器现有面积进行对比,发现A1＋A2比蒸发器现有面积小,说明现有蒸发器的面积比实际需要的面积要大,因此我们可以减小蒸发器的面积来达到优化蒸发器的目的。     

变对流换热系数时针状肋片中的传热分析

本文以针状肋为研究对象，对换热系数沿长度方向变化时肋片中的传热进行了分析与求解，并提出了当量换热系数的概念．使变换热系数问题可转化为常换热系数问题来分析．文中还给出了对变截面的肋片进行数值求解得到的结果．     

The Field-Trap Effect in Heat Transfer under Conditions of Boiling of Dielectric Liquids in External Electric Fields

An experimental study is made into the effect of nonuniform external electric fields on local heat transfer under conditions of boiling of liquid nitrogen. A significant increase in the heat-transfer coefficients is observed in field trap sites on heated surfaces.     

垂直烧结多孔层通道内沸腾传热机理

在总结多年来系列试验研究基础上，提出了垂直烧结多孔层上沸腾传热的物理模型。描述了多孔层内沸腾热及流运过程，同时考虑了多孔层上液膜流速及厚度对多孔层内气流流动及传的影响。这些方面的研究为潜在的工业应用提供了理论论据。     

四川省某地源热泵工程地下换热性能测试

对工程试验井(双U垂直埋管)分别进行了初始地温测试、制冷工况测试、制冷工况后地温恢复测试、制热工况测试和制热工况后地温恢复测试,明确了工程区域内的地下换热量指标。     

管壳式换热器强化传热的数值模拟分析

阐述了换热器管程强化传热强化管和管内插入物两种结构及其性能特点，并用场协同原理和数值模拟方法分析了其强化传热机理。模拟分析的结果为：光滑管内，速度矢量与温度矢量二者之间的夹角接近90℃，传热效果较差；在管内插入物情况下，两者之间的夹角小于90℃，流场和温度场的协同性更好，从而实现了强化传热。     

直接接触式蓄冷装置喷射传热特性的研究

本文通过试验选择适合于直接接触式蓄冷装置的喷射装置的型式,并对喷孔数、喷孔直径对直接接触式换热的影响进行了试验研究。     

传热规律对卡诺热泵生态学优化准则的影响

以反映热泵供热率π与热泵熵产σ、低温热源温度TL和可逆传热系数CPC乘积CPCTLσ之间的折衷“生态学”准则E＝π－CPCTLσ为目标,研究了卡诺热泵在传热规律q∝Δ(T^Nn）时的优化问题,得到了最大E准则时的供热系数和相应的供热率。     

Q∝(△T)n时不可逆卡诺制冷机的生态学最优性能

利用有限时间热力学理论,综合考虑热阻、热漏及其它内不可逆性,研究了传热规律服从Q∝(△T)n时不可逆制冷机的生态学优化性能,并由数值算例对不同损失、不同传热规律情况下的卡诺制冷机性能变化规律进行了比较,其结果对实际制冷机的设计工作具有一定的理论指导意义。     

套管换热器传热过程强化实验系统的研制

多套管式换热器结构简单,清洗、维修方便,易实现加工制作,提出多套管式换热器对套管换热器进行传热强化.在设定条件下编写程序,对多套管换热器进行优化设计,计算显示在相同条件下多套管式换热器与单套管换热器相比传热系数有较大的提高.系统中设置回热器,有效节约能源.该系统在有余热、废热可以利用的场合节能效果更加显著.     

竖直多孔表面通道内液氮沸腾换热实验研究

在液氮自然循环流动时，对竖直多孔表面管管内沸腾换热及外管单面加热时竖直多孔表面套管内沸腾换热，进行了实验研究，分析并讨论了通道的当量半径、热流密度及含气率对沸腾换热的影响。     

烧结多孔层通道内沸腾传热特性研究

用试验研究并分析了垂直烧结多孔层通道内道间隙、粒度、层厚及视观高度对沸腾传热的影响。研究表明，对在同一热流下存在一个最佳通道间隙及粉末粒度范围。适当增大多孔层厚度将有利于沸腾传热系数的提高，而热虹吸高度的降低将不利于沸腾传热系数的增大。