Impact of Relative Humidity of Supply Gas on Temperature Distributions in Single Cell of Polymer Electrolyte Fuel Cell When Operated at High Temperature

For improving the performance of stationary PEFC （polymer electrolyte fuel cell） system, the cell operating temperature up to 90℃ will be preferred in Japan during the period from 2020 to 2030. To understand the operation of the PEFC system under relatively high temperature conditions, detail heat and mass transfer analysis is required. The purpose of this study is to analyze the impact of relative humidity of supply gas on temperature distribution on the backside of separator in single ceil of PEFC using Nation membrane at higher temperature e.g. 90℃. The in-plane temperature distribution when power was being generated was measured using thermograph with various relative humidity of supply gases. It was found that the in-plane temperature distribution at the anode was more even than that at the cathode irrespective of the relative humidity of supply gas at the anode and the cathode. The temperature elevated along gas flow through the gas channel at the cathode irrespective of relative humidity of supply gas at the anode and the cathode. The in-plane temperature distribution at the cathode was narrower with the increase in Tini irrespective of relative humidity of supply gas at the cathode, while it was not observed when changing the relative humidity of supply gas at the anode. When the relative humidity of supply gas at cathode decreased, the in-plane temperature distribution at the anode was wider compared to decreasing the relative humidity of supply gas at the anode. The study concluded that the impact of relative humidity of supply gas at both anode and cathode had little impact on the in-plane temperature distribution at the cathode.

Impact of Thickness of Polymer Electrolyte Membrane and Gas Diffusion Layer on Temperature Distributions in Polymer Electrolyte Fuel Cell Operated at Temperature around 90℃

Polymer Electrolyte Fuel Cell(PEFC)is desired to be operated at temperature around 90℃ for stationary applications during the period from 2020 to 2025 in Japan.It can be expected thinner polymer electrolyte membrane(PEM)and gas diffusion layer(GDL)would promote the power generation performance of PEFC at this temperature.The aim of this study is to understand the impact of thickness of PEM and GDL on the temperature profile of interface between PEM and catalyst layer at the cathode(i.e.,the reaction surface)in a single PEFC with an initial operation temperature(Tini).An 1D multi-plate heat transfer model based on temperature data of separator measured using thermograph in power generation process was developed to evaluate temperature of the reaction surface(Treact).This study investigated the effect of Tini,flow rate and relative humidity of supply gas on Treact distribution.The study finds that when using thin GDL,the even distribution of Treact – Tini is obtained irrespective of thickness of PEM,Tini and relative humidity conditions.Treact – Tini using Nafion 115 is higher than the other thin PEMs irrespective of Tini and relative humidity conditions.It can be concluded that the even temperature distribution could be achieved by using thin PEM and GDL.

Effects of high temperature and high relative humidity drying on moisture distribution,starch microstructure and cooking characteristics of extruded whole buckwheat noodles

Drying is a key step in starch noodle production.The effects of high temperature(60,70,80°C)and high relative humidity(65%,75%,85%)drying(HTHD)on the moisture distribution,starch microstructure and cooking characteristics of extruded whole buckwheat noodles were investigated.Compared to the conventional hot-air drying(CHAD)at 40°C,the increase in drying temperature(60–80°C)and the decrease in relative humidity(85%–65%)significantly improved drying efficiency of the extruded noodles.By adjusting drying temperature and relative humidity,the rate of moisture migration in noodles and phase transition of starch could be appropriately controlled.The optimum drying parameters(T70H75,70°C drying temperature and 75%relative humidity)showed smooth and dense network structure,resulting in the lowest cooking loss(6.61%),broken rate(0%),highest hardness(1695.17 g)and springiness(0.92).However,the total flavonoid content(TFC)and the total phenolic content(TPC)reduced by 6.81%–28.50%and 7.19%–53.23%in contrast to CHAD,and the color of buckwheat noodles became darker through HTHD.These findings showed the potential of HTHD for increasing drying efficiency and improving buckwheat noodle quality.The appropriate drying parameters could maintain a balanced relationship between moisture migration in noodles and phase transition of starch,which resulted in better cooking quality for extruded whole buckwheat noodles.Such a study is valuable for regulating the process conditions of buckwheat-based foods and promoting its commercial utilization.

Numerical Analysis of Temperature Distributions in Single Cell of PEFC by Heat Transfer Model Considering Vapor Transfer

Polymer Electrolyte Fuel Cell(PEFC)is required to be operated at temperature at 100℃ for fuel cell vehicle applications during the period from 2020 to 2025 in Japan.It is expected that micro porous layer(MPL)and thinner polymer electrolyte membrane(PEM)would enhance the power generation performance of PEFC at this temperature.The key objective of this study is to analyse the impact of MPL and thickness of PEM on the temperature distributions of interface between the PEM and catalyst layer at the cathode(i.e.,the reaction surface)in a single PEFC.A 1D multi-plate heat transfer model,considering vapor transfer,which is based on temperature data of separator measured using thermograph in power generation process.It is developed to evaluate temperature at the reaction surface.This study is investigated the effect of flow rate and relative humidity of supply gases on temperature distribution on reaction surface.The study reveals that the impact of flow rate of supply gas on temperature distribution on reaction surface is smaller with and without MPL.It is observed that the even temperature distribution on reaction surface as well as higher power generation performance can be obtained with MPL irrespective of thickness of PEM and relative humidity conditions.

水泥改性生土材料热湿性能及周期性边界下墙体温湿度分布特性

为了揭示周期性边界下生土墙体温湿度分布特性,实验制备水泥改性生土材料并测试其热湿性能,建立一维非稳态热湿耦合传递模型,分别以吐鲁番夏至日和冬至日气象数据为室外边界条件,对冬夏两季水泥改性生土墙体内部温湿度进行数值求解。结果表明:水泥改性生土材料具有良好的吸湿性,水泥掺量的增加能够提升材料的吸湿能力,但是对水蒸气透过性不利。夏季,水泥改性生土墙体对环境温湿度波动衰减效果明显,0.3 m厚水泥改性生土墙体具有理想的隔热和调湿性能。然而,减小墙体厚度会导致冬季墙体内壁面温度显著降低,需考虑必要的保温处理。

基于灰色关联性分析及差异化配粉的锅炉水冷壁超温诊断调整

针对塔山电厂3号锅炉深调期间水冷壁局部超温的问题,将灰色关联性分析引入超温诊断,采集30个常见影响参数构成比较序列,通过计算灰色关联性系数快速锁定磨出力为主要影响因素。通过倒磨及变磨组出力试验分析了其对水冷壁局部超温的影响规律,在此基础上,提出一种基于四角粉量差异化分配的水冷壁局部超温调节方法,将A、B磨#3角、#4角粉量分别同时按照-5%、-6%、-7%调整,前墙最高壁温分别降低22℃、37℃、53℃,最终达到440℃;右墙最高壁温分别降低11℃、17℃、36℃,最终达到432℃,降幅明显,其余邻近点壁温也得到显著降低。为解决超临界机组在低负荷下水冷壁局部超温问题提供了一种创新且行之有效的技术思路。

Experimental Investigation on Local Behaviors of PEMFC with Segmented Cell

When designing a cell stack and developing an operational strategy for proton exchange membrane fuel cell,it is critical to characterize the local current,water and heat.To measure distributions of current density,relative humidity and temperature for both anode and cathode simultaneously along the straight parallel flow channels,this paper uses a segmented tool based on the multilayered printed circuit board flow field plates with embedded sensors.In this study,two kinds of experimental operations of fuel cell reactants are carried out for comparison:the co-flow operation with identical gas flow direction of hydrogen and air and the counter-flow operation with opposite gas flow directions.The detected relative humidity(RH)distributions of both anode and cathode indicate that the asymmetry of RH distribution at two sides of the membrane in counter-flow operation is better at holding water inside the fuel cell compared with the co-flow operation.The in situ measured performance distributions show that segments around the middle of the fuel cell contribute the highest current in counter-flow operation,while for co-flow operation,the current peak locates near the outlet of reactants.

气流组织形式对壁面湿源空间结露规律影响的模拟研究

以防护工程内部湿源的产湿特点为研究对象,建立"壁面散湿湿源模型",进行气流组织形式对室内温湿度和壁面结露分布规律影响的数值模拟研究。通过提出模型空间温湿度分布和壁面结露的三维非稳态数学模型,利用FLUENT对模型进行数值计算,分析研究不同气流组织形式下"壁面散湿湿源模型"的室内温湿度分布规律,并通过编制的壁面结露计算程序,对结露时间、结露面积、结露量以及结露速率进行分析,模拟不同气流组织形式对壁面结露动态发展过程的影响。