Numerical Analysis of Heat Transfer and Gas Flow in PEM Fuel Cell Ducts by a Generalized Extended Darcy Model

Abstract

In this work, gas flow and heat transfer have been numerically investigated and analyzed for both cathode/anode ducts of proton exchange membrane (PEM) fuel cells. The simulation is conducted by solving a set of conservation equations for the whole domain consisting of a porous medium, solid structure, and flow duct. A generalized extended Darcy model is employed to investigate the flow inside the porous layer. This model accounts for the boundary-layer development, shear stress, and microscopic inertial force as well. Effects of inertial coefficient, together with permeability, effective thermal conductivity, and thickness of the porous layer on gas flow and heat transfer are investigated.     

水膜除尘器利用碱性废水脱硫试验研究

水膜除尘器是目前应用较多的除尘装置，在水膜除尘器上利用碱性废水脱硫，脱硫率可达４５％左右，具有以废治废，实施方便 ，脱硫成本低等特点，有较好的推广应用价值。如要获得更高的脱硫率，必须对水膜除尘器作一定的改进。     

重庆市企业环境信用评价体系建设存在的问题及解决路径研究

目前,建设完善的可操作性强且适合重庆的企业环境信用评价体系是健全重庆市市场经济体制、防范经济金融风险的需要,是重庆市社会信用体系建设的重要内容,也是"诚信重庆"建设的重要环节.通过对重庆市企业环境信用评价体系进行分析,指出了评价体系中存在的评价指标不合理、评价周期长、公众参与度不够、评价结果公信力不足等问题,并从建立评价指标与管理成效响应关系、提高评价过程透明度、加大评价结果运用等方面提出了建立完善重庆市企业环境信用评价体系的解决路径.     

Determination of urine-derived odorous compounds in a source separation sanitation system

Source separation sanitation systems have attracted more and more attention recently.However, separate urine collection and treatment could induce odor issues, especially in large scale application. In order to avoid such issues, it is necessary to monitor the odor related compounds that might be generated during urine storage. This study investigated the odorous compounds that emitted from source-separated human urine under different hydrolysis conditions. Batch experiments were conducted to investigate the effect of temperature, stale/fresh urine ratio and urine dilution on odor emissions. It was found that ammonia, dimethyl disulfide, allyl methyl sulfide and 4-heptanone were the main odorous compounds generated from human urine, with headspace concentrations hundreds of times higher than their respective odor thresholds. Furthermore, the high temperature accelerated urine hydrolysis and liquid–gas mass transfer, resulting a remarkable increase of odor emissions from the urine solution. The addition of stale urine enhanced urine hydrolysis and expedited odor emissions. On the contrary, diluted urine emitted less odorous compounds ascribed to reduced concentrations of odorant precursors. In addition,this study quantified the odor emissions and revealed the constraints of urine source separation in real-world applications. To address the odor issue, several control strategies are recommended for odor mitigation or elimination from an engineering perspective.     

硫磺尾气处理装置腐蚀与防护技术

阐述炼油厂硫磺尾气处理装置中常见的的腐蚀问题，介绍防腐蚀技术的进展和应用情况，对装置的防腐蚀提出参考性意见。采用正确的防腐结构设计和先进的工艺防腐控制、严格的工艺生产操作及合理的材料选择，可控制和减轻装置腐蚀，确保环保和安全双达标。     

山地城市灾害系统模糊风险评价

灾害风险是当前灾害研究的热点和核心之一。从灾害系统整体角度,厘定区域灾害系统风险,明晰灾害系统风险要素构成及其作用机制,对于科学指导区域综合防灾减灾具有重要意义。在山地城市灾害系统研究的基础上,基于"R=H×E×S/C"的灾害系统模糊风险概念模型,构建了反映山地城市灾害系统"致灾因子危险性、承灾体暴露性、灾损敏感性和防灾减灾能力"四个方面的"山地城市灾害系统模糊风险评价指标体系";提出了对山地城市灾害系统模糊风险进行定量评价与排序的"综合赋权(AHP-EVM)"二级模糊综合评判模型。在上述研究基础上,以重庆市38个区县作为研究对象,对理论模型进行了实证研究,并从整体上初步阐明和解释了山地城市(重庆市)38个区县的灾害系统模糊风险等级及成因。研究得出以下结论:(1)基于"综合赋权"模糊综合评判的"山地城市灾害系统模糊风险"评价结果科学、可靠,能够从整体反映山地城市灾害系统模糊风险水平及其构成。经过与灾情数据对比、专家评判,本研究所得评价结果通过验证,且与"模糊物元评价"所得结果基本一致。(2)重庆市灾害系统模糊风险整体水平居中。其中,渝中区、江北区,渝东北的城口县、奉节县以及渝东南的酉阳县,灾害系统风险等级高,各类灾害发生及造成损失的可能性较大,是未来防灾减灾工作的重点。     

部分城市空气中颗粒物的元素组成比较

通过对数浓度图和分歧系数对中国广义、武汉、兰州和重庆4座城市空气中粗细颗粒物的42种元素组成进行了比较。结果表明，与人类活动有关的污染元素主要富集在细颗粒物中，而粗颗粒物中元素相对于细颗粒物来说更多的来自于土壤；同一座城市内城区同郊区相比，元素污染更严重，城郊之间细颗粒物中元素在短距离和有利地形下传输作用十分明显。同时还比较了城市之间的元素污染程度。结果表明，兰州城区相对于其它采校点位颗粒物中元素污染较为     

Changes in susceptibility of beech (Fagus sylvatica) seedlings towards Phytophthora citricola under the influence of elevated atmospheric CO2 and nitrogen fertilization

The growth-differentiation balance hypothesis (GDBH) predicts changes in susceptibility of plants against herbivores with changing resource availability. In the presented study we tested the validity of the GDBH for trees infected with a root pathogen. For this purpose Fagus sylvatica seedlings grown under different atmospheric CO₂- and soil nitrogen regimes were infected with the root pathogen Phytophthora citricola. High nitrogen supply increased total biomass of beech regardless of the CO₂-treatment, whereas elevated CO₂ enhanced biomass only in the high nitrogen treatment. The responses of beech under the different growing regimes to the Phytophthora root infection were not in line with the predictions of the GDBH. Enhanced susceptibility of beech against P. citricola was found in seedlings grown under elevated CO₂ and low nitrogen supply. Fifteen months after inoculation these plants were characterized by enhanced water use efficiency, by altered root-shoot ratios, and by enhanced specific root tip densities.     

气相色谱法测定土壤中菊酯类农药残留

以正己烷/丙酮混合溶剂(体积比为1∶1)为提取剂,采用Florisil柱净化、气相色谱电子捕获检测器测定土壤中菊酯类农药残留,优化了提取条件。4种菊酯类农药在0.010 mg/L~1.00 mg/L范围内线性良好,方法检出限为0.005 mg/L~0.010 mg/L,甲氰菊酯回收率为85.2%~103%,RSD为2.3%~5.4%;氯氰菊酯回收率为80.5%~103%,RSD为2.8%~6.7%;氰戊菊酯回收率为80.2%~103%,RSD为2.3%~6.0%;溴氰菊酯回收率为80.8%~103%,RSD为2.4%~6.2%。     

碱性过硫酸钾氧化-气相分子吸收光谱法测定水中总氮

采用碱性过硫酸钾氧化-气相分子吸收光谱法测定水中总氮,用螺纹盖聚四氟乙烯消化管代替比色管,称重法校正体积,加大NaOH用量,讨论了干扰及消除办法。方法在0μg~20.0μg范围内线性良好,检出限为0.016 mg/L,标准溶液平行测定的RSD≤1.5%,实际水样加标回收率为99.2%~102%,测量结果的扩展不确定度为3.3%。