水平螺旋槽管壁面液膜传热特性的研究--流体性质对液膜厚度的影响

考虑到薄膜表面张力和重力的影响,利用流体力学的基本方程建立了小流量液体在水平螺旋槽管外管壁形成壁面液膜的流动和强化传热的拟线性模型,得到了液膜厚度的解析表达式,进而分析了流体性质对壁面液膜厚度的影响。结果表明：对于同一种喷淋液体水,随着温度的升高,液膜厚度受表面张力和槽道表面曲率的影响逐渐减弱,液膜厚度趋向于均匀一致,具有更好的传热传质性能;用水作喷淋液体和煤油、原油相比较,有其特殊的优点,所以工业上常用水作为喷淋式换热器的喷淋液。     

气液降膜流动传热传质研究的综述

气液降膜是工业中常见的传热传质过程,在很多领域中有着广泛的应用,在湿空气透平（HAT）循环的主要部件饱和器中,也有着重要的意义。本文回顾了降膜分别在气体剪切力下以及由界面相变引起的热非平衡状态下的流动稳定性及传热传质的发展现状和研究进展,总结了气液降膜流动已有的理论和实验结果,并展望了气液降膜流动技术的发展前景。     

强化凝结与液膜传热过程的板壳式换热器波纹方案

板壳式换热器敝开的板外侧通道可以实现多种板式换热器所不能实现的传热过程，特别是液膜传热伟质过程。针对不同过程的特点设计波纹的波型是板壳式换热器推广应用的关键，文章介绍了适合于凝结过程的同向双尺度波纹板片和适合于吸收，蒸发等液膜传热传质过程的交叉双尺度波纹板片方案。     

气液两相流动及沸腾传热流体模化分析

基于制冷剂类物质热物性表与水和水蒸气热力性质图表,计算并比较了R12、R22、R123、R134a在相同气液密度比条件下模化水热力过程的能力;应用相似原理与量纲理论分析了流体模化方法在研究气液两相流动特性、高温高压传热过程、临界热流密度现象以及近临界和超临界传热方面的优势与方法.结果表明:制冷剂类物质具有良好的热力性质,其中R134a在相同气液密度比条件下的压力值仅约为水的1/5,而且其臭氧消耗潜能值为0,是环境友好的理想模化流体.提出并探讨了从本质上革新准则数以及基于模型探索新的模化条件和发展新的准则关系式的流体模化技术发展思路.     

电场对管内凝结液膜厚度的影响

以R123为工质,对圆柱形电极进行了电场强化管内凝结换热的试验研究,提出并计算了当量液膜厚度。试验换热管为垂直套管式,外层为冷却水路,内层为工质回路。电压范围为0～30 kV,热流密度范围为4～6 kW/m2。实验观察到了凝结液膜的减薄,在给定的实验条件下,当电压超过5 kV后,随着电压的增加,凝结换热系数增加,当量液膜厚度减小。实验结果表明,液膜厚度的减薄是电场强化凝结换热的主要原因。     

汽-气凝结气膜分布及对换热特性的影响

基于双边界层理论,考虑气膜内诱导速度、气液界面剪切力和压力梯度等因素的影响,建立了在水平管外汽-气凝结换热过程中所形成气膜厚度的数学模型,并讨论了气膜分离情况.结果表明:沿管壁向下,气膜厚度逐渐增大;当气膜发生分离时,气膜厚度在分离点处急剧增大,且随流速增大而减小;当气膜不发生分离时,气膜厚度在管壁底部附近急剧减小,且随流速增大而增大;气膜厚度随壁温升高而增大,随不凝结气体质量分数增大而增大;气膜厚度及气膜分离对换热特性有一定的影响.     

液膜蒸发强化传热表面的传热与流动特性分析

提出一种新的液膜蒸发强化换热表面－波纹丝网换热表面，在丝网结构尺寸进行６种改变后，通过对其传热和流动表面规律的研究，发现合适的优化结构可广泛应用于蒸发冷却系统中。     

狭窄通道内液膜蒸发传热研究

建立了适于蒸发传热过程的数学模型，得出了液膜与气流之间的换热规律，实验分析了有关影响因素。     

等温压缩空气储能系统液气传热特性研究

等温压缩空气储能（I CAES）无需补燃、能源利用率高且碳排放低,在大规模储能领域具有重要应用前景。在建立喷雾的I CAES系统的液气传热模型基础上,通过数值方法分析了喷雾流量对I CAES液气传热特性的影响规律。结果表明：采用喷雾方法能够有效抑制压缩和膨胀过程的温度变化、强化液气传热并实现理想I CAES过程;增大喷雾流量能够降低压缩功耗、提高膨胀做功并降低停机储气过程压损,可提高系统指示效率和储能效率。     

竖直螺旋槽管壁面液膜在蒸发/冷凝时的传热特性的研究

研究竖直螺旋槽管壁面液膜在传热条件下的液膜形成及流动特性，建立了单组分流体的物理和数学模型并得出解析解，且分析了壁面液膜在蒸发，冷凝及无热传输时的液膜厚度分布及速度分布，结果表明，液膜的形状主要受表面张力影响，在表面内弯处流膜较厚，而在槽道起始部液膜较薄，相对于光滑直管，竖直螺旋槽管壁面液膜具有均匀的厚度分布和更好的传热传质性质，特别在冷凝时壁面液膜更薄且分布更加均匀。     

Laminar film condensation heat transfer of hydrogen and nitrogen inside a vertical tube

There have been a number of experimental investigations on condensing heat transfer to cryogenic fluids. The investigations with nitrogen and oxygen have shown reasonable agreement between experimental data and those predicted by Nusselt's theory. On the other hand, in the previous investigations with much colder fluids, such as hydrogen, deuterium, and helium, the experimental condensing heat transfer coefficients are smaller than those predicted by Nusselt's theory, and these differences become much larger when the film Reynolds number or decreasing temperature difference across the condensate film is decreased. In the present investigation, hydrogen and nitrogen were condensed inside a vertical tube (d = 15 mm, L = 30 mm) under steady‐state conditions, respectively, and condensing heat transfer coefficients were precisely measured. From the experimental results, the condensing heat transfer coefficients for saturated hydrogen and nitrogen vapors agree with those predicted by Nusselt's theory within ±20%. The results of the present study suggest that deuterium and helium might also behave as predicted by Nusselt's theory. © 2001 Scripta Technica, Heat Trans Asian Res 30(7): 542–560, 2001     

水平螺旋槽管降膜流动和传热特性研究

对水平螺旋槽管壁面降膜形成及传热特性进行了理论和实验研究,得到了液膜厚度及速度的解析及数值解.结果表明,降膜液膜特性主要受槽道结构和液膜表面张力控制.管壁温度沿周向向下逐渐升高,而且在定热流密度下保持不变,而液膜温度则沿周向逐渐上升.相比光管,螺旋槽管降膜具有更高的传热系数.     

Research on a new heat transfer model for liquid film convective evaporation in annular flow

Based on the phenomenon of turbulence restraint in liquid‐vapor interface, an analytical model is proposed for annular flow with a velocity distribution. The liquid‐vapor interface affecting district mixing length model was amended, and a new liquid film convective evaporation heat transfer model at the annular flow was developed. Compared with the experimental data, the results show that the new model is better than the model based on full tube flow velocity distribution. © 2002 Wiley Periodicals, Inc. Heat Trans Asian Res, 31(7): 524–530, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.10051     

管外冷凝强化换热管的结构及发展趋势

介绍了各种类型的管外冷凝强化换热管,分析了其强化机理及结构特点,并总结得出:管外冷凝强化管的换热系数与管型有关,且各管型的结构参数对强化传热具有重要的作用.对国内外管外冷凝强化技术研究工作进行分析,结果表明,目前管外冷凝强化换热管的研究主要集中于翅片形状、翅片密度、翅片高度等结构参数对换热性能的影响.强化换热管的冷凝传热性能不仅与翅片结构参数有关,而且也与管材的表面特性和导热系数有关.管外冷凝强化换热管的研究重点是开发新型三维结构翅片的双侧强化管并研究其传热关联式,以及研究不锈钢等低成本材料制造的强化管换热管的传热性能和强化结构的优化.     

Influence of processing conditions of polymer film on dropwise condensation heat transfer

The effect of processing conditions of polymer film on dropwise condensation heat transfer of steam under atmospheric pressure is investigated to find an effective technique to prepare a viable polymer film sustaining long-term dropwise condensation pattern state. The polytetrafluoroethylene (PTFE) films were coated on the external surfaces of brass tubes, copper tube, stainless steel tube and carbon steel tube by means of the dynamic ion-beam mixed implantation technique, with a variety of surface processing conditions. The experimental results indicated that heat flux is increased by 0.3-4.6 times and condensation heat transfer coefficient by 1.6-28.6 times of film condensation values for the brass tubes treated with various conditions. The surface processing condition is crucial to the adhesion between polymer film and metal substrate, different substrate material requires different optimal processing condition, and leads to different condensation heat transfer characteristic.     

Two‐phase flow convective condensation of refrigerant mixtures under gas/liquid injection

The influence of gas/liquid injection on two‐phase flow condensation heat transfer characteristics of some refrigerant mixtures in horizontal enhanced surface tubing is presented. Correlations were proposed to predict the impact of the gas/liquid injection on the heat transfer characteristics such as average heat transfer coefficient of R‐507, R‐404A, R‐410A, and R‐407C in two‐phase flow condensation inside enhanced surface tubing. The data also revealed that gas, liquid and gas/liquid injection is beneficial at certain gas/liquid injection ratios to the heat transfer coefficient depending upon the Reynolds number and the condensation point of the refrigerant mixtures in question. It was also evident that the proposed condensation correlations and the experimental data were applicable to the entire heat and mass flux, investigated in the present study under gas/liquid injection conditions. The deviation between the experimental and predicted under gas/liquid injection were less than ± 10, for the majority of data. Copyright © 2005 John Wiley & Sons, Ltd.     

混合气体横向冲刷水平管时对流冷凝换热的机理研究

采用修正的膜模型与Nusselt凝结理论相结合的方法，对含湿混合气体以一定速度冲刷水平管外时对流冷凝换热进行研究，在考虑气相边界层分离的情况下讨论了液膜流动和换热的情况，同时研究了气体来流冲刷角度对总体换热的影响。结果表明，冷凝液膜是一个相当薄的膜层，液相导热热阻在整个换热的过程中基本可以忽略。     

Theoretical research of convective condensation heat transfer for mixture gas on a horizontal tube

The mechanism of convective condensation heat transfer of moist mixed gas across a horizontal tube was studied in this paper. The models referring to how the liquid film flows and the heat transfers on the tube are set up by combining modified film model and Nusselt condensation theory. The effects of Re number, wall temperature, and water vapor concentration on condensation heat transfer are discussed. Results predict that the film thickness profile on the tube is influenced greatly by vapor shear force on liquid film. Local Nusselt number depends remarkably on gas phase heat resistance, which is different from pure vapor and very similar to single‐phase gas. © 2007 Wiley Periodicals, Inc. Heat Trans Asian Res, 36(6): 324–333, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20169     

Mechanism research of convective condensation heat transfer for a gas mixture flowing over a horizontal tube

The modified film model combined with Nusselt's condensation theory are used for the study of convective condensation heat transfer on a horizontal tube with moist mixed horizontal gas flows at a given speed. A theoretical model considering gas boundary layer separation was set up. The liquid film flows and the heat transfer on the tube are presented. The effects of the flow direction on condensation heat transfer are discussed. The results predict that the condensate film is so thin that the liquid phase heat resistance can be ignored. © 2008 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20238