多喷嘴射流式分离器内气固流动特性的数值模拟

基于商用软件Fluent 6.3.26,采用雷诺应力模型及DPM离散相模型并结合理论分析,对基于喷嘴造旋的射流式分离器内两相流动特性进行了模拟计算,得到了较为全面的两相流动规律与细节.结果显示,分离器内部切向速度峰值可达160 m·s^-1,自由涡区的切向速度约为130 m·s^-1,旋流强度明显高于传统旋风单管;沿轴向下,下行流流量逐次减少,其中稳流体顶部下行流降低最为明显,下行流减少致使颗粒卷入内旋流概率增加,分离效果下降;分离器内部局部存在顶部贴壁射流、射流区二次流及灰斗口旋涡流等次级流动;分离器压降约为27.43 kPa,喷嘴区内外旋流能耗分别为4.57 kPa(21.8%)、5.76 kPa(27.6%),稳流体区内外旋流能耗分别为5.85 kPa(27.6%)、4.01 kPa(18.9%);分离器对应的切割粒径较小,约为1.6 μm,极限粒径约为10 μm,符合工业应用要求;基于所建颗粒受力模型及模拟条件下,分离空间可分离的临界粒径为1～2 μm,3 μm及以上颗粒的逃逸浓度小于 0.15 g·m^-3,满足下游烟机对气流的净化要求.     

四氢呋喃和一氟二氯乙烷水合物颗粒聚结特性

实验研究了四氢呋喃（THF）水合物和一氟二氯乙烷（HCFC-141b）水合物颗粒聚结特性,将实验得到的水合物颗粒聚结粒度分布（PSD）与正态分布、对数正态分布、伽马分布、威布尔分布拟合曲线对比,探讨了初始四氢呋喃溶液和一氟二氯乙烷溶液浓度以及搅拌速度对水合物颗粒聚结的影响,并对四氢呋喃水合物和一氟二氯乙烷水合物颗粒特性进行了对比。结果表明,四氢呋喃水合物和一氟二氯乙烷水合物颗粒聚结粒径符合对数正态分布;初始溶液浓度越低、搅拌速度越大,水合物颗粒聚结粒径越小,可以起到防治水合物颗粒聚结的作用;四氢呋喃水合物颗粒粒径是一氟二氯乙烷水合物颗粒粒径的1.3倍左右,从成浆输送的角度来说,一氟二氯乙烷水合物颗粒更易于在管道中输送。     

Hydrogen diffusivity in aluminium measured by a glow discharge permeation method

The diffusion coefficient of hydrogen in aluminium has been determined in the temperature range between 446 and 681 K by a glow discharge permeation method which enables us to extend the temperature range of measurements by enhancement of the permeation flux in spite of the small equilibrium solubility of hydrogen in solid aluminium. The temperature dependence of the diffusion coefficient of hydrogen in aluminium shows a linear Arrhenius relationship with the pre-exponential factor (6.1 ± 0.5) × 10⁻⁵ m² s⁻¹ and with the activation energy (54.8 ± 0.4) kJmol⁻¹. These values are higher than those estimated by several previous authors with hydrogen evolution techniques in high temperature regions. However, the present values are well consistent with the results by Ishikawa and McLellan using an electrolytic permeation method around room temperature, suggesting that hydrogen atoms in aluminium diffuse by the interstitial mechanism in the whole temperature range.     

Optimum energy evaluation and life cycle cost assessment of a hydrogen liquefaction system assisted by geothermal energy

In this study, analyses of the thermodynamic performance and life cycle cost of a geothermal energy-assisted hydrogen liquefaction system were performed in a computer environment. Geothermal water at a temperature of 200 °C and a flow rate of 100 kg/s was used to produce electricity. The produced electricity was used as a work input to liquefy the hydrogen in the advanced liquefaction cycle. The net work requirement for the liquefaction cycle was calculated as 8.6 kWh/kg LH₂. The geothermal power plant was considered as the work input in the liquefaction cycle. The hydrogen could be liquefied at a mass flow rate of 0.2334 kg/s as the produced electricity was used directly to produce liquid hydrogen in the liquefaction cycle. The unit costs of electricity and liquefied hydrogen were calculated as 0.012 $/kWh and 1.44 $/kg LH₂. As a result of the life cycle cost analysis of the system, the net present value (NPV) and levelized annual cost (LAC) were calculated as 123,100,000 and 14,450,000 $/yr. The simple payback period (N_spp) and discount payback period (N_dpp) of the system were calculated as 2.9 and 3.6 years, respectively.     

Fuzzy Integral Filters: Properties and Parallel Implementation

Fuzzy integrals as image filters provide a standard representational form which generalize linear filters such as the averaging filter, morphological filters such as flat dilations and erosions, and order statistic filters such as the median filter. However, fuzzy integral filters are computationally intensive. Computing the output value obtained by fuzzy integral filtering at a point involves sorting all the pixels in a neighborhood of the point according to their values and then computing ordered weighted sum or maximum with respect to an appropriate fuzzy measure. In this paper we discuss some properties of fuzzy integral filters and describe a method for enhancing the processing elements of single instruction, multiple data (SIMD) mesh computers with comparators and counters to efficiently implement fuzzy integral filters.     

Ozonation aided mesophilic biohydrogen production from palm oil mill effluent

Ozone pretreatment of palm oil mill effluent (POME) was employed to improve sustrate biodegradability prior to biological H₂ production. The H₂ production was conducted at varing pHs from 4.0 to 6.0 to examine the impact of pH on the H₂ mesophilic production (37 °C). The optimal pH for H₂ production was 6.0 for both raw and ozonated POME. The POME concentrations were greatly influenced the yields and rates of H₂ production. At the optimal pH, the maximum H₂ production yield of 182 ± 7.2 mL.g⁻¹ COD (7.96 mmoL.g⁻¹ COD) was achieved at the ozonated POME concentration of 30,000 mg COD.L⁻¹. The maximum H₂ production rate (R_max) of 43.1 ± 2.5 mL.h⁻¹ was obtained at the ozonated POME concentration of 25,000 mg COD.L⁻¹. The highest total COD removal was 44% at of 15,000 mg COD.L⁻¹ ozonated POME. Acetic and butyric acids were dominant products during H₂ fermentation and tended to increase with the increased POME concentrations. Ozonation as a pretreatment process showed significant enhancement of the POME biodegradability , and subsequently improved the H₂ production H₂.     

Modular design of an open-source,networked embedded system

The ever increasing hardware capabilities typical of modern microcontrollers make it easier to add more and more functions to embedded systems, even for relatively low-end ones. In turn, this raises new requirements on their firmware, focusing on aspects like adherence to international and industrial standards, modularity, portability, fast time to market, and integration of diverse software components.This paper shows, by means of a case study, how to design a full-fledged networked embedded system using only open-source components, including a small-scale real-time operating system. In addition, it highlights how different components addressed key design issues, like inter-task synchronization and communication.     

砂层劈裂–压密注浆模拟试验系统研发及试验

劈裂–压密模式是砂层注浆扩散过程的主要模式之一。为研究砂层劈裂–压密注浆扩散过程,研发了一套可视化注浆模拟试验系统,该系统由模拟试验架、地应力加载模块、动态监测模块以及注浆控制模块4部分构成,可实现劈裂–压密注浆扩散过程的可视化模拟。以青岛地区含黏性土砂层为典型被注介质,开展了砂层劈裂–压密注浆模拟试验,揭示了注浆扩散过程中劈裂通道形态、注浆压力、应力场以及位移场随时间变化规律,获得了试验条件下的砂层劈裂–压密注浆影响范围。研究结果表明:砂层注浆起裂方向与劈裂通道扩展方向均与大主应力方向一致,浆脉厚度在浆脉扩展方向上存在明显衰减;注浆会引起与劈裂通道垂直方向的应力增加,且该应力沿劈裂通道扩展方向衰减,但注浆对平行劈裂通道扩展方向的应力没有显著影响;劈裂–压密注浆对劈裂通道两侧砂层的影响范围非常有限(20～40cm)。最后从单孔注浆量、钻孔布置方面对砂层劈裂–压密注浆设计方法提出了改进建议。     

Heat transfer and exergy analysis of cascaded latent heat storage with gravity-assisted heat pipes for concentrating solar power applications

A thermal network model is developed to predict the performance of latent heat thermal energy storage (LHTES) systems including cascaded phase change materials (PCMs) and embedded heat pipes/thermosyphons. Because the design of LHTES systems involves a compromise between the amount of energy stored, the heat transfer rate, and the quality of the released thermal energy, an exergy analysis is also carried out to identify the preferred LHTES design. It is found that the LHTES with the lowest melting temperature PCM yields the highest exergy efficiency. However, a cascaded LHTES recovers the largest amount of exergy during a 24 h charging–discharging cycle. Quantitatively, the cascaded LHTES recovers about 10% more exergy during a 24 h charging–discharging cycle compared to the best non-cascaded LHTES considered in this work.     

Characterization of transition to turbulence in microchannels

This paper reports on an experimental study characterizing the laminar-turbulent transition for water flow in circular microtubes. Microtubes with diameters in the range 16.6–32.2 μm of varying length were employed over the Reynolds number range 300–3400. The volume flowrate was measured for an imposed pressure differential using a timed displacement technique. Additionally, the viscous heating-induced mean fluid temperature rise was measured. Two independent approaches were used to identify transition from laminar to turbulent flow. Both methods showed transition to occur in the Reynolds number range 2100–2500, consistent with macroscale tube flow behavior.