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排序方式: 共有3978条查询结果,搜索用时 15 毫秒
1.
《International Journal of Hydrogen Energy》2022,47(38):17010-17021
In the present study, a membrane-based air-to-air planar humidifier (MAPH) with baffle-blocked flow channels and a common MAPH are fabricated, tested and compared. These MAPHs are well thermal insulated from their surroundings. Polyoxymethylene (POM) plates with some unique properties such as large tensile and flexural strength, high chemical resistance and high stiffness are used to create channels at dry and humid sides of MAPHs. The obtained findings revealed that the higher heat and water transfer rates and smaller dew point approach temperature (DPAT) in entire tested flow rates occurs in baffle-blocked MAPH. To evaluate the MAPH performance with considering the pressure drop, a dimensionless parameter, performance evaluation criteria (PEC), is introduced. At flow rates less than 1 m3/h, PEC is less than 1, indicating a decline in MAPH performance with considering the pressure drop. In baffle-blocked MAPH using water trap in the inlet of dry side leads to the performance deterioration. Additionally, the increased relative humidity (RH) of humid side inlet causes an increase in DPAT, consequently, the performance deterioration. 相似文献
2.
《International Journal of Hydrogen Energy》2022,47(80):34244-34256
A conducting and anticorrosive coating is crucial for the application of metal bipolar plates (BP) in proton exchange membrane fuel cell (PEMFC). In this work, a Ti3C2Tx (T)-carbon black (C)-acrylic epoxy (AE) coating is prepared on 304 stainless steel (SS) with enhanced corrosion resistance and conductivity. The corrosion resistance of the T-C-AE coating is investigated in a 0.5 M H2SO4 solution as compared to the AE, T, and T-AE coatings. The T-C-AE coated 304SS exhibits the strongest corrosion resistance with the most positive corrosion potential and the lowest corrosion current density of 0.00673 μA cm?2 in all the samples, while retaining intact and compact surface morphology with the lowest metal ion dissolution even after immersed for 720 h. The addition of Ti3C2Tx and carbon black into the AE matrix greatly decreases interfacial contact resistance (ICR), and the T-C-AE coating achieves a low ICR of 15.5 mΩ cm?2 under 140 N cm?2 compaction force. The excellent anticorrosion performance is mainly attributed to the physical barrier and the cathodic protection provided by the stacked Ti3C2Tx (MXene) nanosheets in the T-C-AE coating. This eco-friendly, conducting, and anticorrosive T-C-AE coating has a good application prospect on SS BP of PEMFC. 相似文献
3.
Kangho Park Woo‐Bin Jung Kiok Kwon Oleg D. Lavrentovich Hee‐Tae Jung 《Advanced functional materials》2019,29(26)
Directed self‐assembly (DSA) using soft materials is an important method for producing periodic nanostructures because it is a simple, cost‐effective process for fabricating high‐resolution patterns. Most of the previously reported DSA methods exploit the self‐assembly of block copolymers, which generates a wide range of nanostructures. In this study, cylinders obtained from supramolecular dendrimer films with a high resolution (<5 nm) exhibit planar ordering over a macroscopic area via guiding topographical templates with a high aspect ratio (>10) and high spatial resolution (≈20 nm) of guiding line patterns. Theoretical and experimental studies reveal that this property is related to geometrical anchoring on the meniscus region and physical surface anchoring on the sidewall. Furthermore, this DSA of dendrimer cylinders is demonstrated by the non‐regular geometry of the patterned template. The macroscopic planar alignment of the dendrimer nanostructure reveals an extremely small feature size (≈4.7 nm) on the wafer scale (>16 cm2). This study is expected to open avenues for the production of a large family of supramolecular dendrimers with different phases and feature dimensions oriented by the DSA approach. 相似文献
4.
《International Journal of Hydrogen Energy》2021,46(74):37098-37107
Partial substitution of hydrocarbon fuel with hydrogen can effectively improve small-scale combustion system stability and performance, potentially opening the way for novel compact power generation and/or propulsion systems in the future. In this study, the effects of hydrogen enhancement between 0% and 40% hydrogen volumetric fractions in methane fuel were experimentally observed in a mesoscale burner array subjected to external acoustic perturbations. The mesoscale burner array utilizes an array of swirl-stabilized burner elements and their interactions with neighboring elements to improve the overall flame stability and simultaneously reduces the combustor length scale. OH1 chemiluminescence and OH planar laser-induced fluorescence (OH-PLIF) were used to image various hydrogen-enriched flames at an equivalence ratio of 0.7, subjected to transverse acoustic perturbations at 320 Hz. Two acoustic modes were imposed by controlling the phase difference between two speakers perturbing the flow. OH1 chemiluminescence images exhibited flame length scale reduction, leading to a denser flame array. Also, flame arrays with higher hydrogen enrichment were found to be more robust against transverse acoustic perturbations, demonstrated by reduced fluctuations in the global heat release rate. OH-PLIF images showed that flames with higher hydrogen enrichment initiated V- to M-shaped flame shape transition even under fuel lean conditions, thereby improving the combustion stability. OH-PLIF images were also used for flame stability analysis through spectral proper orthogonal decomposition (SPOD). The SPOD analysis showed hydrogen enrichment diminished flame fluctuation structures under fuel lean operation. 相似文献
5.
Somnath Karmakar 《Polycyclic Aromatic Compounds》2019,39(2):159-171
Eigensolutions of {X( = C,B,N),Y( = C,B,N)}-cyclacene graphs with next nearest neighbor (nnn) interactions have been obtained in analytical forms by adapting n-fold rotational symmetry followed by two-fold rotational symmetry (or a plane of symmetry). Expressions of eigensolution indicate the subspectral relationship among such cyclacenes with an even number of hexagonal rings e.g., eigenvalues of {X,Y}-di-cyclacene are found in the eigenspectra of all such even cyclacenes. Total π-electron energies and highest occupied molecular orbital and lowest unoccupied molecular orbital (HOMO–LUMO) gaps are calculated using the analytical expressions obtained and are found to vary negligibly with the variation of nnn interactions in such cyclacenes. Total π-electron energy is found to increase due to increase in restriction intensity of nnn interactions, whereas the HOMO–LUMO gap of polyacenecs having the even number of hexagonal rings and with one electron at each site (atom) decreases with increase in the restriction intensity since such systems contain degenerate half-filled HOMO (bonding or nonbonding) that are much more vulnerable for perturbations imposed through nnn interactions. 相似文献
6.
针对平面并联机构无奇异位置工作空间求解困难、过程繁琐、计算量大等问题,提出了基于CAD求解平面并联机构工作空间的三维螺旋扫描方法。将[n]自由度平面并联机构分解成[n]条支链进行独立分析,得到每条支链下末端执行器的可达区域,再将所有支链可达区域取交集即为平面并联机构工作空间。应用SolidWorks软件建立平面并联机构模型,进行几何特征处理,通过自动求解器求解,将求解过程图形化,快速得到同轴布局5R机构和平面3-RPR并联机构的无奇异位置工作空间。通过同轴布局5R机构的运动学实验,验证了该求解方法的可行性。 相似文献
7.
8.
C.A. Ramírez-Herrera M.M. Tellez-Cruz J. Pérez-González O. Solorza-Feria A. Flores-Vela J.G. Cabañas-Moreno 《International Journal of Hydrogen Energy》2021,46(51):26110-26125
Polypropylene (PP) nanocomposites with multi-walled carbon nanotubes (MWCNT) alone or combined with carbon nanofibers (CNF) at different loadings have been fabricated by melt mixing with a focus on their mechanical properties and corrosion resistance for bipolar plates applications in proton exchange membrane fuel cells (PEMFCs). The incorporation of up to 20 wt% MWCNT in the PP matrix produces enhancements of 71, 47, 56, and 30% in microhardness, elastic modulus, and tensile and flexural strength, respectively. Combined additions of MWCNT and CNF allow producing hybrid nanocomposites with increased strength than when neat MWCNT as reinforcement, preserving their processability even at a total filler content of up to 30 wt%. The measured values of icorr in both PP/MWCNT and PP/MWCNT/CNF suggest a slow degradation rate in the PEMFC environment. Based on the US Department of Energy (DOE) targets, PP/20MWCNT, PP/21.5MWCNT, and PP/15MWCNT/15CNF nanocomposites are good candidates to produce bipolar plates for PEMFCs. 相似文献
9.
《International Journal of Hydrogen Energy》2021,46(79):38983-38991
Water electrolysis is a process that can produce hydrogen in a clean way when renewable energy sources are used. This allows managing large renewable surpluses and transferring this energy to other sectors, such as industry or transport. Among the electrolytic technologies to produce hydrogen, proton exchange membrane (PEM) electrolysis is a promising alternative. One of the main components of PEM electrolysis cells are the bipolar plates, which are machined with a series of flow distribution channels, largely responsible for their performance and durability. In this work, AISI 316L stainless steel bipolar plates have been built by additive manufacturing (AM), using laser powder bed fusion (PBF-L) technology. These bipolar plates were subjected to ex-situ corrosion tests and assembled in an electrolysis cell to evaluate the polarization curve. Furthermore, the obtained results were compared with bipolar plates manufactured by conventional machining processes (MEC). The obtained experimental results are very similar for both manufacturing methods. This demonstrates the viability of the PBF-L technology to produce metal bipolar plates for PEM electrolyzers and opens the possibilities to design new and more complex flow distribution channels and to test these designs in initial phases before scaling them to larger surfaces. 相似文献
10.
《International Journal of Hydrogen Energy》2020,45(23):13101-13107
The unitized regenerative fuel cell (URFC) system has attracted significant attention and interests because of its round-trip energy conversion with high energy density. However, the identification of low-cost bipolar (BP) plate with higher corrosion resistance is required to produce a sustainable system. In this work, we investigated the possibilities of using cost-effective lead (Pb) metal-based plate as a BP plate material for URFC system. To further enhance the advantageous properties of Pb plate, silver (Ag) was coated onto the Pb plate. Different types of structural and microstructural analyses (XRD, XPS, SEM, EDAX, and mapping) were conducted to characterize the properties of Pb-based plate and the presence of Ag-coated layer on the surface of Pb plate. When compared with the Pb plate, the Ag-coated Pb plate exhibited a higher water contact angle. The obtained water contact angles of Pb and Ag-coated Pb plates were 77.83° and 92.21°, respectively. The obtained water contact angle of the Ag-coated Pb plate is quite acceptable in the URFC system because it offers exceptional advantages during the URFC operation. Furthermore, the interaction between Pb plate and Ag coated layer resulted in an efficient electrochemical performance. Based on these results, we could conclude that the Pb-based BP plate can be possibly considered for the URFC applications. 相似文献