敷膜多孔纸全热交换器效率的实验及数值研究

针对全热交换器传湿效果不明显的特点,提出了以带孔纸为支撑层,涂敷亲水膜的方式提高交换膜的热效率。基于所采用的交换膜,实验测量了多孔纸膜的热质交换性能;同时,建立了有限元数值仿真模型,研究了不同孔径、孔间距对全热交换器换热效果的影响。结果表明:对于全热交换器而言,采用敷膜多孔纸的方式,可以有效提高全热交换器的换热效率,实验结果与数值模拟结果相符。在带孔纸能够起到支撑层作用的前提下,孔密度越大越好,结合实际加工工艺特点,多孔纸膜中孔的直径应该控制在1 mm左右。为全热交换膜段优化设计提供了热设计参考数据。

使用玻璃纤维的多孔纸

1.前言用火焰法制取的超细玻璃纤维的特点是具有耐酸性,另外,因纤维的截而呈圆形,而纵横比较大,就可制成空隙度高达90％以上的过滤器,片料等。该制晶一般用于隔热、吸声领域。本文介绍可作高性能空气过滤器(简称HEPA)的滤纸和密封式铅蓄电池用隔离片。

多孔碳纸上电沉积镍硫合金及其表征

以多孔碳纸为基体,在25°C下以恒电流电沉积方法制备了Ni–S合金。电镀液的组成为NiSO_4·6H_2O 60.0 g/L,Na_2S_2O_3·5H_2O 16.0 g/L,Na_3C_6H_5O_7·2H_2O 14.0 g/L,(NH_4)_2SO_4 29.8 g/L。通过X射线衍射、扫描电镜、能谱分析等测试手段对所得复合材料的微观结构、形貌和组分进行了表征。结果表明,在碳纸上得到的镍硫合金镀层致密均匀,硫和镍沉积到碳纤维的表面和由碳纤维形成的微孔中,镀层的含硫量为9.89%(质量分数)。测得0.2C倍率下该复合材料作为锂硫电池正极的首次放电比容量为940 mA·h/g。

Paper-derived cobalt and nitrogen co-doped carbon nanotube@porous carbon as a nonprecious metal electrocatalyst for the oxygen reduction reaction

The oxygen reduction reaction(ORR)is a vitally important process in fuel cells.The development of high‐performance and low‐cost ORR electrocatalysts with outstanding stability is essential for the commercialization of the electrochemical energy technology.Herein,we report a facile synthesis of cobalt(Co)and nitrogen(N)co‐doped carbon nanotube@porous carbon(Co/N/CNT@PC‐800)electrocatalyst through a one‐step pyrolysis of waste paper,dicyandiamide,and cobalt(II)acetylacetonate.The surface of the hierarchical porous carbon supported a large number of carbon nanotubes(CNTs),which were derived from dicyandiamide through the catalysis of Co.The addition of Co resulted in the formation of a hierarchical micro/mesoporous structure,which was beneficial for the exposure of active sites and rapid transportation of ORR‐relevant species(O2,H+,OH?,and H2O).The doped N and Co formed more active sites to enhance the ORR activity of the electrocatalyst.The Co/N/CNT@PC‐800 material exhibited optimal ORR performance with an onset potential of 0.005 V vs.Ag/AgCl and a half‐wave potential of?0.173 V vs.Ag/AgCl.Meanwhile,the electrocatalyst showed an excellent methanol tolerance and a long‐term operational durability than that of Pt/C,as well as a quasi‐four‐electron reaction pathway.The low‐cost and simple synthesis approach makes the Co/N/CNT@PC‐800 a prospective electrocatalyst for the ORR.Furthermore,this work provides an alternative approach for exploring the use of biomass‐derived electrocatalysts for renewable energy applications.

Bifunctional 3D n-doped porous carbon materials derived from paper towel for oxygen reduction reaction and supercapacitor

Designing and fabricating cheap and active bifunctional materials is crucial for the development of renewable energy technologies.In this article,three-dimensional nitrogen-doped porous carbon materials(NDPC-X,in which X represents the pyrolysis temperature) were fabricated by simultaneous carbonization and activation of polypyrrole-coated paper towel protected by a silica layer followed by acid etching.The material had a high specific surface area(1,123.40 m^2/g).The as-obtained NDPC-900 displayed outstanding activity as a catalyst for the oxygen reduction reaction(ORR) as well as an electrode with a high specific capacitance in a supercapacitor in an alkaline medium.The NDPC-900 catalyst for the ORR exhibited a more positive reduction peak potential of à0.068 V(vs.Hg|HgCl^2) than that of Pt/C(-0.121 V),as well as better cycling stability and stronger methanol tolerance.Moreover,the NDPC-900 had a high specific capacitance of 379.50 F/g at a current density of 1 A/g,with a retention rate of 94.5% after 10,000 cycles in 6 mol/L KOH electrolyte when used as an electrode in a supercapacitor.All these results were attributed to the effect of a large surface area,which provided electrochemically active sites.This work introduces an effective way to use biomass-derived materials for the synthesis of promising bifunctional carbon material for electrochemical energy conversion and storage devices.

High-performance salt-resistant solar interfacial evaporation by flexible robust porous carbon/pulp fiber membrane

Solar evaporation has emerged as an attractive technology to produce freshwater by utilizing renewable solar energy.However,it remains a huge challenge to develop efficient solar steam generators with good flexibility,low cost and remarkable salt resistance.Herein,we prepare flexible,robust solar membranes by filtration of porous carbon and commercial paper pulp fiber.The porous carbon with well-defined structures is prepared through controlled carbonization of biomass/waste plastics by eutectic salts.We prove the synergistic effect of porous carbon and paper pulp fiber in boosting solar evaporation performance.Firstly,the porous carbon displays a high light absorption,while the paper pulp fiber with good hydrophilicity effectively promotes the transport of water.Secondly,the combination between porous carbon and paper pulp fiber reduces the water vaporization enthalpy by 20%,which is important to significantly improve the evaporation performance.As a proof of concept,the porous carbon/paper pulp fiber membrane possesses a high evaporation rate of 1.8 kg m^(-2)h^(-1)under 1 kW m^(-2)irradiation.Thirdly,the good flexibility and mechanical property of paper pulp fiber enable the solar membrane to work well under extreme conditions(e.g.,after 20 cycles of folding/stretching/recovery).Lastly,due to the super-hydrophilicity and superwetting,the hybrid membrane exhibits the exceptional salt resistance and long-term stability in continuous seawater desalination,e.g.,for 50 h.Importantly,a large-scale solar desalination device for outdoor experiments is developed to produce freshwater.Consequently,this work provides a new insight into developing advanced flexible solar evaporators with superb performance in seawater desalination.

Comparison of GTN Damage Models for Sheet Metal Forming

The Gurson-Tvergaard-Needleman(GTN) damage model was developed basing on anisotropic yield criterion to predict the damage evolution for anisotropic voided ductile materials.Hill's quadratic anisotropic yield criterion(1948) and Barlat's 3-component anisotropic yield criterion(1989) were used to describe the anisotropy of the matrix.User defined subroutines were developed using the above models.Taking the benchmark of NUMISHEET'93 square cup deep drawing as an example, the effect of matrix plastic anisotropy on a ductile material was studied.The predicted result by Barlat'89-GTN model has a better agreement with the experimental data than that by Hill'48-GTN and the original GTN model.