Thermal and Electrical Analysis in a Solid Oxide Fuel Cell Stack Using a Curved Profile for the Inlet Flow Rate Along the Stacking Direction

This study analyzes the cell temperature and current density fields of a solid oxide fuel cell stack, in which the inlet flow rate along the stacking direction of the fuel is either a curved profile derived through hydraulics or a progressively decreasing profile. The results show that the temperature field was neglibibly affected by the non-uniform inlet profile of the fuel, but the current density distribution was apparently affected. The difference in current density distribution between the curved profile and the progressively decreasing profile was small in the case of an solid oxide fuel cell (SOFC) with 10 stacks, but became larger in an SOFC with 20 stacks. In the 10-stack SOFC, the difference of current density between the uniform inlet flow and the curved inlet flow was less than 3%, whereas the deviation in the curved profile was less than 12%. However, in a 20-stack SOFC, the difference of current density was over 20%, whereas the deviation in the curved profile was more than 50%. Comparing the results between the curved and the progressively decreasing inlet profile indicates that the current density difference was over 20% in the 20-stack SOFC, but below 1% in the 10-stack SOFC. Therefore, a progressively decreasing inlet profile can replace a curved profile for analyzing an SOFC stack when the number of stacks is less than 10.     

Determination of the performance limits of flame arresters at increased oxygen concentrations

This investigation shows how an increased oxygen concentration influences the performance limits of crimped ribbon deflagration flame arresters at elevated pressures. An evaluation of the maximum experimental safe gap (MESG) as reliable criterion for describing the performance limits under non-atmospheric conditions is given. Measurements of MESGs and flame arrester performance tests were performed. Various fuel/oxygen/air mixtures containing ethylene and propane were used as testing gases. Former studies on the pressure dependence and the influence of oxygen on the MESG were initially confirmed. Furthermore, performance tests using a commercial deflagration flame arrester revealed that such a flame arrester may prevent flame transmission also at non-atmospheric conditions within a limited range. For various oxygen concentrations the performance limits were reached at the same MESG. Hence, it can be assumed that a flame arrester possesses a device- and fuel-specific maximum experimental safe gap for a specific gas mixture in different concentrations and at different pressures. This performance-related maximum safe gap can be used as a parameter for estimating and describing the performance limits of a flame arrester. It offers an attempt to simplify the testing and qualification of deflagration flame arresters for non-atmospheric conditions.     

Testing of the Storm Water Management Model Low Impact Development Modules

Stormwater infrastructure designers and operators rely heavily on the United States Environmental Protection Agency’s Storm Water Management Model (SWMM) to simulate stormwater and wastewater infrastructure performance. Since its inception in the late 1970s, improvements and extensions have been tested and evaluated rigorously to verify the accuracy of the model. As a continuation of this progress, the main objective of this study was to quantify how accurately SWMM simulates the hydrologic activity of low impact development (LID) storm control measures. Model performance was evaluated by quantitatively comparing empirical data to model results using a multievent, multiobjective calibration method. The calibration methodology utilized the PEST software, a Parameter ESTimation tool, to determine unmeasured hydrologic parameters for SWMM’s LID modules. The calibrated LID modules’ Nash–Sutcliffe efficiencies averaged 0.81; average percent bias (PBIAS) ?9%; average ratio of root mean square error to standard deviation of measured values 0.485; average index of agreement 0.94; and the average volume error, simulated vs. observed, was +9%. SWMM accurately predicted the timing of peak flows, but usually underestimated their magnitudes by 10%. The average volume reduction, measured outflow volume divided by inflow volume, was 48%. We had more difficulty in calibrating one study, an infiltration trench, which identified a significant limitation of the current version of the SWMM LID module; it cannot simulate lateral exfiltration of water out of the storage layers of a LID storm control measure. This limitation is especially severe for a deep LIDs, such as infiltration trenches. Nevertheless, SWMM satisfactorily simulated the hydrologic performance of eight of the nine LID practices.     

Performance of activated carbon coated graphite bipolar electrodes on capacitive deionization method for salinity reduction

• Graphite bipolar electrodes act as an appropriate bed for the CDI process. • Activated carbon Coating improves the application of the electrodes. • CDI is an environmentally friendly method to apply for brackish water. • Initial concentration is the most important parameter in the CDI method. • CDI process in a batch-mode setup needs more development. This research investigates a capacitive deionization method for salinity reduction in a batch reactor as a new approach for desalination. Reductions of cost and energy compared with conventional desalination methods are the significant advantages of this approach. In this research, experiments were performed with a pair of graphite bipolar electrodes that were coated with a one-gram activated carbon solution. After completing preliminary tests, the impacts of four parameters on electrical conductivity reduction, including (1) the initial concentration of feed solution, (2) the duration of the tests, (3) the applied voltage, and (4) the pH of the solution, were examined. The results show that the maximum efficiency of electrical conductivity reduction in this laboratory-scale reactor is about 55%. Furthermore, the effects of the initial concentration of feed solution are more significant than the other parameters. Thus, using the capacitive deionization method for water desalination with low and moderate salt concentrations (i.e., brackish water) is proposed as an affordable method. Compared with conventional desalination methods, capacitive deionization is not only more efficient but also potentially more environmentally friendly.     

Estimation of the liability to detonating of prilled ammonium nitrate fertiliser grade

The statistical analysis of the results of testing liability to detonation of coated and uncoated prilled ammonium nitrate was performed. The correlation between the crushing of the lead cylinders as a result of the so-called 4″ tube test and the chemical as well as the physical properties of ammonium nitrate were determined. The results demonstrated that the liability to detonation of ammonium nitrate may be estimated by use of mathematical equations, which employ easily obtainable experimental values relating to the chemical composition and physical properties of the tested fertilisers.     

Biomechanical pulping: a mill-scale evaluation

Mechanical pulping process is electrical energy intensive and results in low paper strength. Biomechanical pulping, defined as the fungal treatment of lignocellulosic materials prior to mechanical pulping, has shown at least 30% savings in electrical energy consumption, and significant improvements in paper strength properties compared to the control at a laboratory scale. In an effort to scale-up biomechanical pulping to an industrial level, 50 tons of spruce wood chips were inoculated with the best biopulping fungus in a continuous operation and stored in the form of an outdoor chip pile for 2 weeks. The pile was ventilated with conditioned air to maintain the optimum growth temperature and moisture throughout the pile. The control and fungus-treated chips were refined through a thermomechanical pulp mill (TMP) producing lightweight coated paper. The fungal pretreatment saved 33% electrical energy and improved paper strength properties significantly compared to the control. Since biofibers were stronger than the conventional TMP fibers, we were able to reduce the amount of bleached softwood kraft pulp by at least 5% in the final product. Fungal pretreatment reduced brightness, but brightness was restored to the level of bleached control with 60% more hydrogen peroxide. The economics of biomechanical pulping look attractive.     

A multi-flowpath model for the interpretation of immiscible displacement experiments in heterogeneous soil columns

This work focuses on the phenomenon of the immiscible two-phase flow of water and oil in saturated heterogeneous soil columns. The goal is to develop a fast and reliable method for quantifying soil heterogeneities for incorporation into the relevant capillary pressure and relative permeability functions. Such data are commonly used as input data in simulators of contaminant transport in the subsurface. Rate-controlled drainage experiments are performed on undisturbed soil columns and the transient response of the axial distribution of water saturation is determined from electrical measurements. The transient responses of the axial distribution of water saturation and total pressure drop are fitted with the multi-flowpath model (MFPM) where the pore space is regarded as a system of parallel paths of different permeability. The MFPM enables us to quantify soil heterogeneity at two scales: the micro-scale parameters describe on average the effects of pore network heterogeneities on the two-phase flow pattern; the macro-scale parameters indicate the variability of permeability at the scale of interconnected pore networks. The capillary pressure curve is consistent with that measured with mercury intrusion porosimetry over the low pressure range. The oil relative permeability increases sharply at a very low oil saturation (< 10^− 3) and tends to a high end value. The water relative permeability decreases abruptly at a low oil saturation (~ 0.1), whereas the irreducible wetting phase saturation is quite high. The foregoing characteristics of the two-phase flow properties are associated with critical (preferential) flowpaths that comprise a very small percentage of the total pore volume, control the overall hydraulic conductivity, and are consistent with the very broad range of pore-length scales usually probed in soil porous matrix.     

分布式光纤测温技术在隧道火灾和渗漏探测中的应用

隧道火灾和渗漏一直是隧道安全和健康的重要问题。基于分布式光纤测温系统(DTS)具有能实现在线实时监测且实测温度随光纤沿程分布这一技术特点和优势,将单根分布式光纤应用于隧道火灾的预警预报、火灾定位、隧道渗漏定位,属国内首创。本文介绍了DTS测温原理和实测成果。实测情况表明,DTS系统测温精确,抗干扰性强,特别适合隧道火灾预警预报和渗漏探测,具有良好的应用前景。     

Determination of PCBs, PCDDs and PCDFs in insulating oil samples from stored Chinese electrical capacitors by HRGC/HRMS

Homologue and congener profiles of polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in commercial PCBs formulations are key information for the source identification of PCBs contamination as well as for the risk assessment caused by potential exposure. The isotope dilution technology in combination with high resolution gas chromatography-high resolution mass spectrometry (HRGC/HRMS) has made the accurate determination of such profiles possible. So far, various commercial PCB formulations except Chinese products have been successfully determined. Two PCBs containing insulating oil samples from stored Chinese electrical capacitors have been determined with the same methodology for comparability. The total concentration PCBs in two oil samples were 790 000 μg g⁻¹ and 720 000 μg g⁻¹, respectively. TriCBs, TetraCBs, and DiCBs were found to be most abundant. Concentration of dioxins contamination in two samples is 650-670 ngTEQ g⁻¹, of which 69-71 ngTEQ g⁻¹ from PCDD/Fs with the predominant congeners of 1,2,7,8-TeCDF; 2,3,7,8-TeCDF; 2,3,4,7,8-PeCDF and 1,2,3,7,8-PeCDF. The contributions of DL-PCBs in total TEQ in both samples were more than 85%. The dioxin-like toxicity in insulating oils contained in electrical capacitors could be considered receive attention as an important dioxins source if such wastes are not managed in an environmentally sound manner.     

五氯酚标准样品的研制

五氯酚是美国ＥＰＡ公布的１２９种重点污染物名单以及我国环境优先监测污染物黑名单中的重点污染物,也是环境监测和环境科研工作中的主要对象。本文介绍了这种污染物毒理特性和液体介质标准样品的分析、研究、制备方法。