HAT循环湿化器内部传热传质实验研究

为了研究湿空气透平(HAT)循环湿化器内部气液两相间的传热传质规律,搭建了高压填料湿化器实验系统,并自主开发了加压气液两相温度和相对湿度测量装置,得到15个工况下湿化器内湿空气温度(气温)、水的温度(水温)以及相对湿度沿湿化器高度的分布规律,研究了水气比、进口水温对湿化器内湿化过程的影响规律。结果表明:气液两相温度分别沿流动方向先降低后升高,湿空气在湿化器底部就已达到饱和状态;水气比对湿化器性能和内部气液参数的影响较大,水气比增大,进口水温升高,同一位置的水温和气温均升高,总体加湿量增大;进口水温升高时,底部湿空气更快达到饱和状态。     

HAT循环后冷湿化过程的传热传质性能研究

为了提升湿空气燃气轮机循环的调控灵活性,自主设计和搭建了后冷湿化器一体化实验系统,通过实验获得不同水气比下后冷湿化器出口空气的温湿度和出口水温,利用实验数据修正表面化学反应速率,基于表面化学反应模型建立了后冷湿化过程三维数值模型,分析了水气比和进口水温对后冷湿化器性能的影响。结果表明：建立的后冷湿化器传热传质模型能高精度模拟后冷湿化过程,空气温度沿流动方向呈逐渐降低的趋势,空气的含湿量和相对湿度沿流动方向逐渐升高;水气比和进口水温均对后冷湿化器的性能有较大影响,随着水气比和进口水温增大出口空气湿度提高,湿化性能提升,而降低水气比有利于提升空气后冷性能。     

逆流式空气湿化器实验系统的研制

增湿湿化器是HAT循环的关键部件，本文利用相位多普勒分析仪Dual PDA(Phase Doppler Analyzer)详细测量湿化器内气液两相流场和内部温度场、相对湿度分布等，掌握传热传质机理以及研究分析影响湿化器性能的主要因素，从而进一步研制设计和改进、完善了湿化器实验系统。     

逆流式空气湿化器热力性能的效率分析

为了详细研究HAT循环关键部件湿化器的热力学性能,用分析的方法定义了湿化器的效率的概念,并结合实验得出了不同进口参数,如湿空气含湿量、水气比和进口水温(水气温差)对效率的影响规律,为提高湿化器性能和确定合理的运行工作状态提供了依据。图4参13     

HAT循环逆流式湿化器的热力性能实验研究及冷却数计算

在理论分析湿化器内部传热传质机理的基础上，进行了湿化器总体热力性能试验，得出了在不同实验工况下，各测量参数对湿化器热力性能的影响规律，同时计算了冷却数，得出了其变化规律。结果表明：随水气质量比的增大，湿化器出口湿空气的温度、温升和出口水温都增大，而冷却数减少。在同一水气质量比下，随进口水温升高，出口湿空气温度、温升和出口水温都增大，冷却数减少。在各实验工况下，湿化器的出口湿空气都具有很高的相对湿度，达到或接近饱和状态。冷却数降低对系统有利，但不是越低越好，应该优化选择最佳值。     

逆流式空气湿化器热力性能的(火用)效率分析

为了详细研究HAT循环关键部件湿化器的热力学性能，用[火用]分析的方法定义了湿化器的[火用]效率的概念，并结合实验得出了不同进口参数，如湿空气合湿量、水气比和进口水温（水气温差）对[火用]效率的影响规律，为提高湿化器性能和确定合理的运行工作状态提供了依据。     

泡沫陶瓷填料湿化器加湿性能实验研究

温化器是湿空气透平(HAT)循环的关键部件,其性能优劣对于循环的性能有着重要的影响.对采用新型SiC泡沫陶瓷填料的湿化器在加压条件下的湿化性能进行了实验研究,分析了水气比、进口水温、操作压力以及进口空气温度对湿化过程的影响,研究表明,提高水气比或进口水温会使进出口空气温差、含湿量差相应增加,湿化器节点温差增大.操作压力...     

有无后冷器的微燃气轮机HAT循环性能比较

基于某80kW微燃气轮机回热循环改造工作,比较了有后冷器和无后冷器的HAT(Humid Air Turbine)循环性能和需要增加的换热器面积。研究结果表明,对于所研究的微燃气轮机,有、无后冷器的HAT循环系统折合效率和折合输出功相当,与有后冷器的HAT循环相比,无后冷器的HAT循环湿化器更高,体积更大,但是由于省掉了后冷器,其总换热面积(后冷器、湿化器、省煤器换热面积之和)更小,即意味着其投资更低,且无后冷器的HAT循环系统结构更简单,将使系统更加紧凑且控制更容易。     

不同应力水平砂岩颗粒料湿化变形试验研究

鉴于颗粒料湿化变形是土石坝、地基基础等工程中变形控制所考虑的重要影响因素,利用外置湿化水头的侧限压缩固结仪,对砂岩颗粒料进行了不同应力水平的湿化试验,研究了单线法湿化变形量与湿化应力、湿化时间的关系;对比了单双线法压缩固结曲线差异,总结了砂岩颗粒料湿化变形规律。试验结果表明,单双线法所测相对湿化变形随湿化应力的变化曲线均呈指数函数关系,此规律在湿化应力较低时吻合程度较高,在湿化应力较高时双线法比单线法所测湿化变形离散性大;所测相对湿化变形差值随湿化应力增大而有减小,最大差值为湿化应力0.10 MPa时的33.63%。单线法所得砂岩颗粒料湿化变形随湿化应力增大而增大,浸水时间相同时应力水平越高,湿化变形越大;随浸水时间增加,颗粒料湿化变形速率先增加后急剧减小,直至趋于稳定。     

大西沟水库粘土心墙过渡性粘土的湿化变形试验研究

土石筑坝材料在库水位快速变化时往往会由于材料湿化产生附加应变,从而影响土石坝的变形及应力应变状态。现状研究集中于粗粒料,对粘土类材料湿化变形的研究很少。为此,结合大西沟水库大坝心墙过渡性粘土,采用“单线法”开展了湿化变形试验。结果表明,粘土材料的湿化变形小于粗粒料,应力水平高时差距更为明显;湿化轴向应变和剪应变关系与粗粒料变化规律相似;粘土的湿化轴向应变和体积应变总体呈线性关系。现有的粗粒料湿化变形经验模型不太适用于反映粘土的湿化剪应变,为此提出了一个综合考虑参数数量和准确度的粘土湿化经验模型以精确描述粘土材料的湿化变形。     

Dynamic modeling and analysis of a shell-and-tube type gas-to-gas membrane humidifier for PEM fuel cell applications

A gas-to-gas humidifier using membranes is the preferred technology for external humidification of fuel cell reactant gases in mobile applications because no extra power supply is required and there are no moving parts. In particular, a shell and tube structure is compact, which allows its easier integration in a fuel cell vehicle.

This paper proposes a mathematical model for the humidifier using the principles of thermodynamics, including analysis of heat and mass transfer and of static and dynamic behaviors. Firstly, the heat and mass transfer behavior was simulated and the results compared with the experimental data. Secondly, the model was used to investigate the sensitivity of the geometric parameters and the effects of various operating conditions on performance. Finally, step responses of the humidifier at various flow rates were analyzed.     

Effect of operating parameters on dynamic response of water-to-gas membrane humidifier for proton exchange membrane fuel cell vehicle

An analytic multi-dimensional dynamic model of a membrane type humidifier has been developed for the study of transient responses of the humidifier under proton exchange membrane fuel cell vehicle operating conditions. The dynamic responses of heat and mass transfer and fluid flow in a membrane humidifier are mathematically formulated and modeled with a newly developed pseudo-multi-dimensional concept. The model is used to analyze the performance of the humidifier under various operating conditions and the dynamic response of the humidifier under transient operating conditions. The simulation results show that, in the case of the water-to-gas type membrane humidifier modeled in this study, the time constant of water diffusion in the membrane is less than 1 s. Thus, the delay of the response of the humidifier induced by the vapor diffusion in the membrane is not significant in vehicle operation. However, it is also found that the dynamic behavior is mainly due to the thermal resistance and heat capacity of the membrane humidifier.     

An experimental study and model validation of a membrane humidifier for PEM fuel cell humidification control

This paper presents an experimental study and model validation of an external membrane humidifier for PEM fuel cell humidification control. Membrane humidification behavior was investigated with steady-state and dynamic tests. Steady-state test results show that the membrane vapor transfer rate increases significantly with water channel temperature, air channel temperature, and air flow rate. Water channel pressure has little effect on the vapor transfer rate and thus can be neglected in the system modeling. Dynamic test results reveal that the membrane humidifier has a non-minimum phase (NMP) behavior, which presents extra challenges for control system design. Based on the test data, a new water vapor transfer coefficient for Nafion membrane was obtained. This coefficient increases exponentially with the membrane temperature. The test results were also used to validate a thermodynamic model for membrane humidification. It is shown that the model prediction agrees well with the experimental results. The validated model provides an important tool for external humidifier design and fuel cell humidification control.     

Effect of inserting obstacles in flow field on a membrane humidifier performance for PEMFC application: A CFD model

In this study, the numerical models are developed to investigate the influence of obstacle shape and number on performance of a planar porous membrane humidifier for proton exchange membrane fuel cell (PEMFC) application. Dew point of dry side outlet and water transfer rate are applied as evaluation parameters of the performance regardless of pressure drop. A dimensionless number named performance evaluation criteria (PEC) is calculated for all models. The higher value of PEC indicates the higher heat transfer rate with lower pressure drop. In humidifier with one rectangular obstacle compared with the simple humidifier, water transfer rate increases by 7.28%. The highest values of water transfer rate, dew point and PEC, also the greatest values of pressure drop are in humidifiers with rectangular, triangular and circular obstacles, in that order. When there is restriction in securing pumping power in fuel cell system, circular obstacle is the best choice. With considering the pressure drop, using one obstacle does not offer any advantage because the PEC is less than one (0.898). At least two obstacles are needed to have PEC number greater than one, consequently an efficient performance. An increment in number of obstacles causes an increment in water transfer rate, dew point and PEC.     

膜加湿器热质交换过程的理论分析

膜加湿器是保证质子交换膜燃料电池(PEMFC)正常高效运行的重要组成部分.以燃料电池的板式膜加湿器为研究对象,根据热质交换原理对膜加湿器的传热传质过程进行了理论计算,分析了空气质量流量、膜内加湿侧进口温度和膜内加湿侧进口湿度对传热传质过程的影响.在传热方面:当空气质量流量不同时,随着膜内加湿侧进口温度的变化,膜内的热流量变化趋势不一致;当膜内加湿侧进口相对湿度为95%时,随着空气质量流量的变化,膜内热流量变化不大.在传质方面:当加湿侧进口相对湿度不变时,膜中水传输速率随着空气质量流量的增大而减小;当空气质量流量不变时,膜中水传输速率随着加湿侧进口相对湿度的增大而增大.     

燃料电池空气系统增湿器建模与仿真

建立气-气增湿器的数学理论模型,并基于Amesim软件建立燃料电池增湿器及空气系统仿真模型,从燃料电池系统层面分析干湿侧不同温度、压力、水含量等输入条件下的干侧出口空气的湿度变化情况,并采用水转移率（water vapor transfer rate,WVTR）对增湿器增湿性能进行评价,结果表明此模型可进行前期验证,能较好地预测汽车运行过程中增湿器的动态响应特性。     

HAT循环饱和器传热传质过程及相似分析

以HAT循环中饱和器为研究对象，讨论了实验研究的相似条件。在简化条件下建立了饱和器内部多相流的控制方程，并给出了相应的边界条件；对这些方程进行了无量纲化处理．根据微分方程的不变性原理，得到了饱和器实验研究中应遵循的相似准则，并对这些准则在实验中作用进行说明，指出了饱和器实验设计中应注意的主要问题。     

直接空冷系统散热器喷雾增湿量研究

在大型直接空冷火电厂的运行中普遍存在夏季因为散热器换热不良引起出力受阻的问题。针对这一问题,各大火电厂一般采用喷雾增湿法降低空冷散热器入口空气温度,改善空冷散热器的换热效果,降低机组背压,从而提高机组出力。通过分析喷雾增湿法的原理,在提出喷雾增湿法的数学模型的基础上,用商用M atlab软件进行了仿真计算。通过仿真计算得出环境温度与喷水量的关系,从而为喷雾增湿法的应用提供了一定的理论依据和运行参考。     

Two dimensional dynamic modeling of a shell-and-tube water-to-gas membrane humidifier for proton exchange membrane fuel cell

Water management is a crucial factor in determining the performance of proton exchange membrane fuel cell (PEMFC) for automotive application. The shell-and-tube water-to-gas membrane humidifier is useful for humidifying the PEMFC due to its good performance. Shell-and-tube water-to-gas membrane humidifiers have liquid water on one side of the tube wall and a dry gas on the other. In order to investigate humidifier performance, a two-dimensional dynamic model of a shell-and-tube water-to-gas membrane humidifier is developed. The model is discretized into three control volumes – shell, tube and membrane – in the cross-sectional direction to resolve the temperature and species concentration of the humidifier. For validation, the dew point temperature of the simulation result is compared with that of experimental data and shows good agreement with only a slight difference. The distribution of humidification characteristics can be captured using the discretization along the air-flow direction. The humidification performance of two different flow configurations, counter and parallel, are compared under various operating conditions and geometric parameters. Finally, the dynamic response of the humidifier at the step-change of various air flow rates is investigated. These results suggest that the model can be used to optimize the inlet flow humidity of a PEMFC.