含湿混合气体水平管外对流冷凝换热实验研究

回收烟气中的潜热和显热在提高锅炉效率和环境保护方面都具有重要意义。主要针对含湿混合气体在水平单管管外的对流冷凝换热进行了实验研究。通过对实验数据的分析,得到了烟气进口温度、冷却水进口温度、水蒸气的质量分数以及Re的变化对含湿混合气体在水平单管管外冷凝换热的影响。     

An Experimental Study on Latent Heat Recovery of Exhaust Wet Flue Gas

The experiment was conducted to investigate the heat transfer performance of wet flue gas in a vertical tube. The factors influencing the convective condensation of wet flue gas were experimentally investigated. The measured results indicate that the convective heat transfer of bulk flow and condensation heat transfer of vapor have significant contribution to the total heat transfer and the dominant transport mechanism is dependent upon the vapor fraction in mixture.     

石墨烯-PFA复合材料换热器与金属换热器的传热性能对比

氟塑料换热器以其耐腐蚀、耐磨损等优点而备受关注,但氟塑料热导率较低,换热能力差,限制了其广泛应用。石墨烯-PFA复合材料兼具石墨烯优异的导热性和可熔性聚四氟乙烯(PFA)良好的耐酸碱腐蚀性,是新一代的换热器材料。搭建了余热回收测试实验台,对石墨烯-PFA复合材料换热器和金属换热器的传热性能进行对比。研究了不同烟气流速、不同进口烟气温度以及不同石墨烯配比对复合材料传热性能的影响。结果表明:对于金属换热器和复合材料换热器,当烟气流速从2.0增加到4.0 m/s时,传热系数分别增加到原来的1.19和1.34倍;随着进口烟温的升高,两种材质的传热系数分别降低了15.6%和14.7%;随着石墨烯含量增加,复合材料的导热系数以及传热系数均增加。     

径向热管换热器在天然气工业炉低温烟气中的应用

当前我国的能源形势紧张,能源利用状况令人担忧.在一些高耗能的企业,工业生产中排放的中低温烟气余热由于回收难度高、回收成本大等问题,一直得不到合理的利用,如何合理回收成为亟待解决的难题之一.简要介绍了一种新型余热利用换热设备——径向热管换热器,提出了计算热管换热器经济性评价指标的方法,并以某工厂低温烟气余热回收工程为实例,对烟气余热的回收利用进行了技术和经济效益分析.实践应用证明,径向热管换热器在工业低温烟气余热回收中有很好的实用性和可行性.     

Research on convective condensation heat transfer for a gas mixture in a vertical tube

This paper discusses the convective condensation of a gas mixture in a vertical tube. A mathematical model was derived by combining a modified film model and Nusselt's condensation theory. The effect of wall temperature on film thickness and interfacial temperature was predicted and film thickness was calculated. When compared with the gas phase resistance method, the film model is better. The phenomenon of SO₂ absorption into condensate is illustrated and discussed. © 2004 Wiley Periodicals, Inc. Heat Trans Asian Res, 33(4): 219–228, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20011     

Condensation heat transfer on tubes in actual flue gas

In order to improve boiler efficiency, latent heat recovery from flue gas is a very important concept. Condensation heat transfer on horizontal stainless‐steel tubes was investigated experimentally by using an actual flue gas from a natural gas boiler. The experiment was conducted at different air ratios of the flue gas and a wide range of tube wall temperatures. The condensation pattern was similar to a dropwise condensation near the dew point. By decreasing the wall temperature, the wall region covered with a thin liquid film increased. The heat and mass transfer behavior was well predicted with the analogy correlation at the high‐wall‐temperature region. At the low‐wall‐temperature region, the total heat transfer was higher than that predicted by the analogy correlation. © 2001 Scripta Technica, Heat Trans Asian Res, 30(2): 139–151, 2001     

椭圆管散热器传热及阻力性能试验研究

对空气横掠片距不相等的叉排椭圆翅片管散热器的传热及阻力性能进行了试验研究,得到试件在一系列工况下的传热与管外流动阻力数据,并对试验数据进行分析计算,从总传热系数K中分离出管外空气侧的对流换热系数h,给出有工程应用价值的管外换热准则关系式及管外阻力准则关系式。认为椭圆管管外的平均换热效果优于圆管。在相同的流通截面积下椭圆管传热周边较长,换热面积相应增加,因此结构上允许布置得更紧凑。     

降低燃气锅炉排烟热损失方法探讨

燃用天然气的锅炉其排烟温度较高，除带走大量显热之外，烟气中还存在大量水蒸汽的潜热，若将这两部分热量充分回收，则将大幅度提高锅炉热效率。文章在对天然气的燃烧特性计算的基础上，分析燃气锅炉烟气潜热回收的效果和需要解决的问题。     

Condensation heat transfer on tubes in actual flue gas (Parametric study for condensation behavior)

In order to improve boiler efficiency, latent heat recovery from the flue gas is a very important concept. Condensation heat transfer on horizontal tubes was investigated experimentally by using flue gas from a natural gas boiler. The parametric studies concerning the effects of tube stages, gas velocities, SO₂ in the flue gas, and Teflon‐lined tubes were conducted at a wide range of tube surface temperature. The heat transfer was enhanced at the second stage due to the wake turbulence of the first stage. No significant decrease of the condensation in the second stage due to the condensate falling from the first stage could be observed. Even at the high gas velocity condition, the condensation pattern was similar to that observed in previous low gas velocity experiments. The effect of SO₂ in the flue gas on the condensation behavior could not be observed. The heat and mass transfer behaviors on stainless‐steel and Teflon‐lined surfaces were well predicted with the analogy correlation. The above results suggested that the heat and mass transfer were dominated by the convection and diffusion process on the gas side. © 2003 Wiley Periodicals, Inc. Heat Trans Asian Res, 32(2): 153–166, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.10079     

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     

The performance study of a wet six-row heat-pipe heat exchanger operating in tropical buildings

The overall effectiveness of a wet six-row wickless heat pipe-heat exchanger (HPHX) for tropical building HVAC systems was simulated using a computer simulation program. This computer program, utilizing Fortran source code, was developed based on the effectiveness-NTU method together with the ridge model for predicting the film condensation and uses the concept of iteration to predict the temperature distribution across the HPHX and its overall effectiveness. The effects of inclination angle and inlet evaporator relative humidity on heat transfer coefficient for the HPHX were determined using TRNSYS Type98 component. The wet HPHX effectiveness and relative humidity were also studied in this research experimentally. Copyright © 2002 John Wiley & Sons, Ltd.     

烟气脱硫系统中热管式换热器流动阻力计算

热管换热器的阻力降问题涉及到其研发、设计、应用以及防腐措施等方面,是热管式换热器研究的一个重要方面。文章尝试使用换热器局部数值模拟、宏观多孔介质模拟以及传统经验公式,用三种不同的计算方法对换热器的流动阻力进行计算,并对其结果进行比较和相互验证,较全面地描述热管式换热器宏观和局部的流动阻力场,为包括脱硫腐蚀研究在内的有关热管换热器的进一步研究提供参考。     

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     

燃气锅炉烟气在滴型管外传热特性的数值分析

在回收燃气锅炉烟气余热时,采用特殊管型强化传热以吸收烟气中大量的水蒸气所携带的显热和潜热,可以降低锅炉的排烟温度,提高锅炉的热效率。对滴型管和圆管烟气侧传热特性进行数值计算,通过对计算结果的分析比较,探讨了影响传热的因素,得出滴型管的传热特性优于圆管的结论,为特殊管型在冷凝换热器中的应用提供参考。     

板式换热器传热和阻力特性的实验研究

利用搭建的液-液型板式换热器试验平台,根据实验数据运用定性雷诺数法拟合出传热关联式,找出Nu与摩擦因子f之间的通用关系式,为板式换热器的设计计算提供了依据。运用传热量与功率的消耗比来评价板式换热器的性能,找出了影响其性能的主要因素,进一步澄清了单纯依靠提高流速来增加传热性能是不经济的。     

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。     

环保用板翅式换热器的数值模拟与试验研究

选取矩形截面平直翅片板翅式换热器的矩形单通道运用fluent软件进行数值模拟。首先对不同波高和波距的三组九种几何尺寸的翅片在同一工况下进行数值模拟,选出每组中传热和阻力综合性能最优者。然后对选出的三种翅片在不同工况下进行数值模拟,最终选出一种传热和阻力综合性能最优的。并对实物换热器进行试验研究,同时将试验结果和数值模拟结果进行对比分析,验证了数值模拟的正确性。     

珠状凝结模型对比研究

珠状凝结与膜状凝结相比是一种高效的、有相变的换热方式,得到了广泛关注。介绍了关于珠状凝结换热在实验和理论模型方面的研究状况,并进行了对比。并且考虑了接触角、促进层以及裸露表面强制对流换热的影响,建立了新的计算珠状凝结换热特性的模型,新模型可以计算不同工况下的不同换热结果。将新模型的计算结果与实验数据进行对比,发现二者较为吻合。为进一步研究珠状凝结换热提供了一定的理论依据。     

Heat transfer research on vapor‐gas mixture with condensation in a vertical tube

The convection‐condensation heat transfer of vapor‐gas mixtures in a vertical tube was studied theoretically and experimentally. The effects of the condensation of a small amount of water vapor (8 to 20%) on heat transfer in a vertical tube were discussed. Comparisons show that theoretical solutions obtained through modified film model and experimental results are in good agreement. The results show that the condensation heat transfer of a small amount of water vapor and single‐phase convection heat transfer in the vapor‐gas mixtures are of the same order of magnitude, and these two modes of heat transfer could not be neglected. © 2002 Wiley Periodicals, Inc. Heat Trans Asian Res, 31(7): 531–539, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.10055     

地源热泵地中换热器的非稳态传热数值研究

竖直U型管经常被用做地源热泵的地下换热器.文章建立了三维数值模型模拟U型管内的流动和地下耦合非稳态传热.使用商业软件GAMBIT和FLUENT构造数值模型并进行数值模拟.为了验证模型的有效性,将U型管出口水温的模拟结果与实测数据进行了比较:运行中出口水温模拟值稍大于实验值,随着运行时间的增加,两者相差越来越小.该结果显示,对于长时间运行的热泵系统,此模型的模拟数据更加真实可靠.