A comparative study of 3E (energy,exergy, and economy) analysis of various solar stills

In this paper, an experimental study of the conventional solar still (CSS), the conventional solar still with glass cooling (CSSGC), the conventional solar still with basin heating (CSSBH), and the conventional solar still with glass cooling and basin heating (CSSGCBH) was carried out on the basis of the distilled water production, the energy efficiency (EnE), the exergy efficiency (ExE), and economic analysis. The CSSGC and CSSBH contain Peltier modules for cooling the glass and heating the basin. The evaporative heat transfer coefficient for all the experimental stills was calculated. The values of daily distilled water production from the CSSGCBH, CSSBH, CSSGC, and CSS were 4.56, 3.79, 2.49, and 1.89 kg/m², respectively. The daily distilled yield of the CSSBH and CSSGCBH were increased by 58.55% and 50.13%, respectively, as compared with the CSS. Moreover, the daily EnE and ExE of the CSSGCBH were 27.03% and 3.5%, respectively, whereas the EnE and ExE of the CSS were 10.88% and 1.3%, respectively. Furthermore, the cost of distilled water production was found to be 0.26, 0.35, 0.53, and 0.64 $/day for the CSS, CSSGC, CSSBH, and CSSGCBH, respectively, if the selling price of the distilled water was Rs10.     

中温烟气旁路技术在变煤种宽负荷脱硝工程运用

随着我国电煤市场变化和火电机组运行灵活性政策出台,许多烟煤锅炉开始燃用褐煤并参与深度调峰,如何适应新煤种并实现宽负荷脱硝成为亟需解决的问题。本文在制粉系统防爆技改基础上,提出了一种中温烟气加热SCR系统入口烟温的技术方案,并结合工程实际运用进行了介绍,为同类型机组参与深度调峰工作提供一定借鉴。     

Fabrication of porous titania sheet via tape casting: Microstructure and water permeability study

In this article, we report the effects of slurry formulation and sintering conditions on the microstructure and permeability of porous titania sheets prepared by tape casting. It was found that solid concentration and binder content in the titania slurry play a vital role in the porosity and microstructure of the sintered titania sheets. Solid concentration and binder content were optimized based on the green tape quality and open porosity of the sintered titania sheets. The optimum solid concentration with the lowest surface roughness was obtained at 0.61 g/cm³. The effects of temperature and sintering time on the open porosity and crystal structure of the final product were also investigated. Increasing the sintering temperature from 1000 to 1100 °C resulted in increasing the pore size from 170 to 264 nm and decreasing the open porosity. Finally, water permeability of the porous titania sheets was studied to evaluate the permeation flux and maximum operating pressure. The results revealed that the permeability of the porous titania sheet is increased not only by increasing the open porosity but also by increasing the pore size.     

7075铝合金热变形连接接头的组织与性能

应用Gleeble-3500热模拟机对7075铝合金进行了热变形连接试验,利用金相显微镜和扫描电镜对不同温度和保温时间的接头界面组织进行了观察和分析,并对接头进行了拉伸性能测试。结果表明:当连接温度为460 ℃,保温时间为24 h时,对界面进行EDS分析,界面处已经没有氧化物的偏聚,此时的力学性能最佳,抗拉强度达到444 MPa,屈服强度为265 MPa。     

淬火温度对G105钢组织和性能的影响

利用硬度计、拉伸试验机、冲击试验机和光学显微镜等手段,研究了G105钢分别在890、910和930 ℃保温150 min淬火,随后进行630 ℃保温180 min回火处理后组织和性能变化。结果表明:随着淬火温度的升高,G105钢淬火硬度越来越高;经回火处理后,淬火温度为890 ℃和910 ℃时,调质硬度无太大差异,分别为33.2 HRC和32.7 HRC,淬火温度为930 ℃的调质硬度相对提高约1.5 HRC。试验钢强度随着淬火温度的升高也呈现升高趋势,但冲击韧性呈先升高后下降的趋势,这主要是由于调质后存在粒状碳化物的析出现象,导致其冲击韧性显著下降,故认为当淬火温度选取910 ℃时,获得的G105钢综合力学性能较佳。     

55SiCr弹簧钢中的残留奥氏体与碳化物

通过扫描电镜(SEM)、电子背散射衍射(EBSD)、透射电镜(TEM)、X射线衍射仪(XRD)、热膨胀仪、洛氏硬度计等手段研究了弹簧钢55SiCr的组织和相变点以及残留奥氏体和碳化物在热处理过程中的组织演变。结果表明:55SiCr弹簧钢淬火后残留奥氏体以块状分布在基体上;随回火温度的升高,残留奥氏体减少并呈粒状和薄膜状分布;C在残留奥氏体中富集,使其稳定性增强;Si抑制了碳化物的析出,提高了残留奥氏体的稳定性。低温回火时,Si延缓了渗碳体析出;高温回火时,C原子扩散速率提高,促进渗碳体析出,引起体积的收缩。慢速加热回火时,C有足够的时间扩散,从而促进渗碳体的形成,使渗碳体的形成温度提前;快速加热回火时,C来不及扩散,抑制了渗碳体的析出。回火加热速率一样时,试验钢的硬度随回火温度的提高而下降。当回火温度为400 ℃时,硬度值最大为51 HRC;当回火温度为650 ℃时,硬度值最小为37 HRC。当加热速率为0.1 ℃/s时,硬度值最小为33 HRC;当加热速率为200 ℃/s时,硬度值最大为40 HRC。     

Structural,microstructural, and magnetic studies of Y3Fe5-xNixO12 garnet nanoparticles

This paper reports the structural and magnetic properties of a series of Y₃Fe_5-xNi_xO₁₂ (x = 0, 0.05, 0.1, and 0.2) nanopowders synthesized by the citrate combustion method. We have discussed the change in different properties with the variation in calcination temperatures as well as the Ni ion substitution in yttrium iron garnet. X-ray diffraction study confirmed the desired garnet phase formation in all the calcined powders, and the crystallinity improved with an increase in calcination temperature. The crystallite sizes were observed in the range 47–52 nm and 84–94 nm for the samples calcined at 800 and 1000 °C, respectively. Scanning electron micrographs confirmed that the grains were in the nanometre range (132–170 nm) at 800 °C and increased (351–363 nm) at 1000 °C. Larger grains at high calcination temperature resulted in the enhanced saturation magnetization and a decrease in coercivity. Curie temperature (T_c) was observed in the range 558–560 K for all the calcined Y₃Fe_5-xNi_xO₁₂ samples. Nickel substitution for iron sites in Y₃Fe_5-xNi_xO₁₂ decreased the saturation magnetization and enhanced the coercivity. This could be related to the substitution of Ni ions for tetrahedral iron sites, which changed the magnetic exchange interactions of different lattice sites. The magnetic anisotropy constant (K) increases with the enhancement of calcination temperature, whereas it decreases with nickel ion substitution in Y₃Fe_5-xNi_xO₁₂. This study suggests that the structural and magnetic properties can be tuned by Ni substitution for the Fe ions in Y₃Fe₅O₁₂ garnets at different calcination temperatures, which make them promising candidates for various technological applications.     

Achieving both large piezoelectric constant and high Curie temperature in BiFeO3-PbTiO3-BaTiO3 solid solution

The high-temperature and high-performance piezoelectric ceramics are required urgently in the petrochemical, automotive, and aerospace industries. In this work, the (0.85-x)BiFeO₃-xPbTiO₃-0.15BaTiO₃ (BF-PT-BT, x = 0.21, 0.22, 0.23, 0.24 and 0.25) piezoelectric ceramics with both high Curie temperature and large piezoelectric constant d₃₃ were presented. X-ray diffraction analysis shows that BF-PT-BT ceramics exhibit dominant perovskite structure with the coexistence of tetragonal (T) and rhombohedral (R) phases. The c/a ratio, Curie temperature, piezoelectric constant, dielectric constant and loss of the BF-PT-BT ceramics for x = 0.23 are 1.06, 546 °C, 222 pC/N, 545 and 0.013, respectively. Room temperature piezoelectric constant of BF-PT-BT ceramics is much higher than those of PbTiO₃, PbNb₂O₆ and other ABO₃ perovskite compounds (BaZrO₃, Bi(Zn, Ti)O₃, PbZrO₃ and Pb(Mg, Nb)O₃) modified ternary BiFeO₃-PbTiO₃ ceramics with similar Curie temperatures. The piezoelectric constant is almost unchanged after BF-PT-BT ceramics was annealed at 450 °C for 30 min, which is due to the stable switched non-180° domain and transformed R phase by annealing treatment.     

A variational approach for free vibrating micro-rods with classical and non-classical new boundary conditions accounting for nonlocal strengthening and temperature effects

Abstract

Transverse vibration of a circular cross sectional micro-rod subjected to a new kind of boundary constraints with elastic torsional springs is presented based on nonlocal elasticity. A nonlocal strengthening beam model is utilized and the effect of temperature changing is taken into consideration. The variational method and Hamilton’s principle are applied to derive the governing equation of motion and corresponding boundary conditions. A higher-order partial differential equation that is a typical characteristic of nonlocal strengthening model is developed, and the boundary conditions contain not only classical conditions but also non-classical higher-order conditions. Unlike previous studies which were only concerned with some conventional boundary constraints, we consider more general boundary conditions named elastic torsional spring supports. Such boundary conditions are between the simply supported and clamped ones, and they are closer to the actual constraints of existing engineering structures. Natural frequencies of micro-rods with new boundary constraints are determined via an eigenvalue method and compared with other results in the literature. It is shown that the nonlocal scale factor, thermal parameter, rigidity parameter and torsional spring coefficient play significant roles in free vibration of micro-rods. The research can provide a reference for a large class of boundary conditions ranging from simply supported to clamped micro-rods.     

GO-nafion composite membrane development for enabling intermediate temperature operation of polymer electrolyte fuel cell

Increasing Polymer Electrolyte Fuel Cells’ (PEFCs) operating temperature has benefits on the performance and the ease of utilisation of the heat generated; however, efforts for high temperature PEFCs have resulted in high degradation and reduced life time. In the literature, conventional low temperature (T < 80 °C) and high temperature (140–200 °C) regimes have been extensively studied, while the gap of operating at intermediate temperature (IT) (100–120 °C) has been scarcely explored.The main bottleneck for operating at IT conditions is the development of a suitable proton exchange membrane with comparable performance and lifetime to the commercially used Nafion operating at conventional conditions. In this work, composite membranes of Graphene Oxide (GO) and Nafion of varied thickness were fabricated, characterised and assessed for in-situ single cell performance under automotive operating conditions at conventional and intermediate temperatures.The material characterisation confirmed that a composite GO-Nafion structure was achieved. The composite membrane demonstrated higher mechanical strength, enhanced water uptake, and higher performance. It was demonstrated that by utilising GO-Nafion composite membranes, an up to 20% increase in the maximum power density at all operating temperatures can be achieved, with the optimum performance is obtained at 100 °C. Moreover, the GO-Nafion membrane was able to maintain its open circuit voltage values at increased temperature and reduced thickness, indicating better durability and potentially higher lifetime.