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。     

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     

湿化器的传热传质机理和性能分析

从传热传质基本原理出发,建立了ＨＡＴ循环的重要部件－湿化器的数学模型,研究了湿化器的工作性能,并指出了目前某些处理方法的不合理之处。     

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。     

土石坝粗粒料的湿化动力特性试验研究

采用大型静动力三轴试验仪对筑坝粗粒料做了常规和湿化三轴试验，研究了粗粒料在湿化变形后动力特性的变化情况，并与常规三轴动力试验结果进行对比。结果表明，粗粒料的动力特性受湿化变形的影响较大，粗粒料的动力性能参数发生了一定程度的衰减，对比分析两种试验的Hardin-Drnevich模型参数，发现湿化变形对k₂、λ_max影响较为明显，数值发生衰减，但对n、k₁的影响不明显。     

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。     

Three-dimensional CFD modeling of a planar membrane humidifier for PEM fuel cell systems

A three-dimensional numerical model is developed to investigate and compare the performance of humidifiers with counter-flow and parallel-flow configurations. This model has a set of coupled equations including conservations of mass, momentum, species and energy. The results indicate that in counter-flow humidifier, water and heat transfer is more than that of the parallel-flow that leads to a higher dew point at dry side outlet, consequently, a better humidifier performance. An increase in temperature and a decrease in mass flow rate at dry side inlet lead to a better humidifier performance. However at the low flow rates the humidifier performance does not change a lot by preheating the inlet dry gas. An increase in relative humidity at dry side inlet does not offer any advantage.     

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 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 on the bubble humidification method of polymer electrolyte membrane fuel cells

A necessary requirement for polymer electrolyte membrane fuel cell (PEMFC) performance is providing sufficient water content in the membrane. The bubble humidifier is the simplest and inexpensive method for PEMFC humidification. In this study, a prototype of bubble humidifier is designed, fabricated, and tested. The effects of water temperature in the reservoir, water level inside the reservoir and inlet air flow on the humidifier performance are investigated. The results show that the outlet air relative humidity decreases (about 6% - 11%) with an increase in the inlet air flow rate from 1 m³ h^?1 to 3 m³ h^?1 at four different water temperatures. The increase in the water temperature and water level inside the reservoir lead to the better humidifier performance. At the water temperature of 20^°C, increasing water level from 5 cm to 7.5 cm has a significant effect on humidifier performance but increasing water level from 7.5 cm to 15 cm does not offer any advantage.     

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.     

Design methodology for membrane-based plate-and-frame fuel cell humidifiers

Currently, polymer electrolyte membrane fuel cells require some method of humidification to operate effectively. External gas-to-gas membrane-based humidifiers can provide an efficient method to recycle exhaust heat and product water from the fuel cell stack. This work describes a design methodology involving a series of design equations for plate-and-frame membrane humidifiers. Humidifiers of different flow channel geometries were created with a rapid prototyping technique. These humidifier units were tested at different operating conditions in an attempt to validate the design equations. The ratio between the residence time of gas in the humidifier over the diffusion time of water from the surface of the membrane into the channel can be used as a design parameter. This ratio was shown to offer a good starting point for humidifier design, and a target range between 2.0 and 4.0 was identified (with a nominal desired value of 3.0). A humidifier design procedure and suggestions are presented based on this parameter and the packaging requirements of the humidifier in a fuel cell system. This algorithm was validated by creating a further prototype humidifier.     

小型太阳能海水淡化装置

基于空气增湿-除湿海水淡化技术,采用热海水与空气逆流对喷的空气加湿器,设计了结合太阳能集热器的小型太阳能海水淡化系统。试验结果表明,该结构的空气加湿器具有很好的加湿效果,出口空气相对湿度可达到98%以上。当喷水温度为60℃、空气流量为11.8 L/s时,该小型海水淡化装置产水率可达3.42 kg/h。     

Modeling and experimental validation of H2 gas bubble humidifier for a 50 kW stationary PEMFC system

Ensuring uniform membrane hydration in a PEMFC (Proton Exchange Membrane Fuel Cell) is important for its performance and durability. In this study, a bubble humidifier for humidifying hydrogen in a 50 kW PEMFC pilot plant was designed, built, and modeled. Initial tests, carried out by humidifying air, show that a dew point temperature of higher than 59 °C is attained when operating the PEMFC plant at nominal power at 65 °C. The model simulation results show good agreement with experimental data and the model is used for studying humidifier performance at other conditions. Steady state simulation results suggest that by increasing the heating water flow rate, the humidifier outlet dew point temperature can be increased by several degrees because of improved heat transfer. Finally, dynamic simulation results suggest that the humidity of the hydrogen can be controlled by manipulating the heat supply to the humidifier.     

Experimental verification of a membrane humidifier model based on the effectiveness method

Experiments conducted on a commercial fuel cell humidifier determined that the water recovery ratio is the best performance metric because it considers the water supplied to the humidifier. Data from a porous polymer membrane with a hydrophilic additive were analyzed under a heat and mass transfer model. The membrane showed low water uptake profiles at relative humidities below 80 percent, and a steep increase in water uptake above threshold.The experiments were conducted with samples of the porous membrane in a single cell humidifier at isothermal conditions at temperatures of 25, 50, and 75 °C. The water recovery ratio for the porous membrane decreased with increasing flow rate.The model was verified experimentally and its predictions agreed with the measured data.     

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.