A new series of Ba-Co-Operovskite-type oxygen carriers has been successfully synthesized by the microwave-assisted sol-gel method and further applied for producing an O2/CO2 mixture gas. The oxygen adsorption/desorption performance of synthesized samples was studied in a fixed-bed reactor system. Effects of A/B-site substitution on the oxygen desorption performance of Ba-Co-O–based perovskites are also included. Furthermore, the effects of operating conditions including the adsorption time and temperature as well as the desorption temperature on oxygen production performance were investigated in detail. The results indicated that BaCoO3-δ exhibited an excellent oxygen desorption performance among the synthesized A/B-site–substituted ACoO3-δ and BaBO3-δ samples, and that the optimal adsorption time, adsorption temperature and desorption temperatureforBaCoO3-δ were determined to be 20min, 850◦Cand850◦C, respectively, in this study.
As one of high energy consumption pumps, pump used for solid-liquid two-phase mixture transportation, such as slurry pump and mud pump, is extensively used in the hydraulic transportation of solid-liquid mixture through pipes in various fields. The erosion wear in slurry pumps has been identified as a critical issue during transportation of slurry as it affects the equipment performance and reduces its reliability and operation life, leading to the waste of energy. Many studies indicate that the performance and efficiency of solid-liquid two-phase centrifugal pump is controlled by the two-phase flow pattern inside the pump, so understanding flow characteristics and abrasion mechanism has important significance to improve the hydraulic design of the impeller for decreasing the abrasion and increasing the service life of the pump. In the present study, based on solid-liquid two-phase flow as object, an improved experimental facility without agitation was developed can improve the test precision by eliminating the influence of agitation on flow inside pump and improving particle-liquid two-phase flow circulation way. On the base of experimental studies, POD methods were applied to analysis the liquid turbulence modulation by solid-particles and the behavior of large eddy structures will be clearly understood. Thus, the theoretical system of the solid-liquid two-phase flow will be further improved. And a theoretical principle for the solid-liquid two-phase pump optimal design will be presented. The following conclusions are obtained: (ⅰ) a superior PIV two-phase test platform than that in the previous literature is designed and it can be very good to realize a stable solid-liquid two-phase flow measurement of centrifugal pump. Compared with the traditional platform, the results obtained by the novel solid-liquid two-phase centrifugal pump PIV test platform has a very high accuracy and it has a good reference value to understand flow mechanism of a centrifugal slurry pump. The two particle images with and without agitating are shown in Figure 5. As can be seen that a large number of bubbles are brought into the circulation line (Figure 5(a)), which is caused by a higher stirring speed for suspending solid particles, and thus the actual flow images shows a gas-liquid-solid three-phase flow. However, for the present test facility without stirring, there is no such problem, and the original image is very clear without bubbles. (ⅱ) The POD analyses show that the solid-particles injection has an important influence on the large scale turbulence structures which contain a large amount of energy. The modal energy distribution as a function of the POD mode number is displayed in Figure 10. The energy contribution of these large scale structures to the total energy becomes larger due to the injection of solid-particles, whereas the contribution of the small scale structures, which denotes the energy dissipation, becomes smaller. This is why the low solid-phase volume concentration has higher pump head and efficiency. The addition of solid-particle increases the friction loss, but reduces the flow separation loss and inhibits the development of small scale vortex. However, with the increase of solid-particle concentration, the friction loss increases is greater than the flow separation loss reduction, and thus pump head and efficiency decrease. The above phenomena show fully that the solid-particles addition has an important influence on the large scale energetic eddy structures. This is confirmed by the measurement results as shown in Figure 11.
Two components reversible temperature sensitive coatings suitable for ABS were prepared with hydroxyl acrylic resin as film forming material,temperature sensitive powder,solvent and various kinds of additives,such as leveling agent,dispersant etc.The effects of different component on coatings property and choosing principle were discussed.The application process and notice of the coatings were briefly introduced.
Purpose The purpose of this paper is to investigate the heat and mass transport characteristics in microchannel reactors with non-uniform catalyst distributions. Design/methodology/approach A two-dimensional model is developed to study the heat and mass transport characteristics in microchannel reactors. The heat and mass transport processes in the microchannel reactors with non-uniform catalyst distribution in the catalytic combustion channel are also studied. Findings The simulated results are compared in terms of the distributions of species mole fraction, temperature and reaction rate for the conventional and new designed reactors. It is found that the chemical reaction, heat and mass transport processes are significantly affected and the maximum temperature in the reactor is also greatly reduced when a non-uniform catalyst distribution is applied in the combustion catalyst layer. Practical implications This study can improve the understanding of the transportation characteristics in microchannel reactors with non-uniform catalyst distributions and provide guidance for the design of microchannel reactors. Originality/value The design of microchannel reactors with non-uniform catalyst distributions can be used in methane steam reforming to reduce the maximum temperature inside the reactor.
Abstract Methanol steam reforming (MSR) is considered as an effective way to provide on‐board hydrogen production technology for fuel cell applications. CuFe 1.2 Al .8 O 4 spinel catalyst was synthesized by sol–gel method and the chemical and physical properties were studied in‐depth. X‐ray diffraction, hydrogen‐temperature programmed reduction (H 2 ‐TPR), BET, and scanning electron microscopy were used to characterize the catalysts with reaction times of 20, 50, and 100 h. The results of H 2 ‐TPR showed that 90% of spinel Cu 2+ was released after 100 h reaction. BET results show that the specific surface area and pore characteristics of the catalyst have not changed greatly after reaction for 20, 50, and 100 h. Furthermore, in the unsteady‐state test, CuFe 1.2 Al .8 O 4 exhibited excellent catalytic activity and thermal stability under long‐term repeated start‐up and stop cycles. At 275°C, the methanol conversion rate remained around 94% and the CO selectivity remained below 1%. Therefore, the catalyst synthesized in this study has excellent stability and low CO selectivity, making it a highly promising on‐board hydrogen production catalyst in the field of HT‐proton exchange membrane fuel cells (PEMFCs).
The shipping industry is trying to use new types of fuels to meet strict pollutant emission regulations and carbon emission reduction targets. Hydrogen is one of the options for alternative fuels used in marine applications. Solid oxide electrolysis cell (SOEC) technology can be used for hydrogen production. When water and carbon dioxide are provided to SOECs, hydrogen and carbon monoxide are produced. The interconnector of SOECs plays a vital role in cell performance. In this study, a 3D mathematical model of cathode-supported planar SOECs is developed to investigate the effect of interconnector rib width on the co-electrolysis of water and carbon dioxide in the cell. The model validation is carried out by comparing the numerical results with experimental data in terms of a polarization curve. The rib width is varied from 0.2 mm to 0.8 mm with an interval of 0.1 mm. It is found that the cell voltage is decreased and then increased as the rib width increases. When the current density is 1 A/cm2, the voltages of SOECs with rib widths of 0.2 mm, 0.6 mm, and 0.8 mm are 1.272 V, 1.213 V, and 1.221 V, respectively. This demonstrates that the best performance is provided by the SOEC with a rib width of 0.6 mm. In addition, the local transport processes of SOECs with different rib widths are presented and compared in detail. This study can provide guidelines for the design of interconnectors of SOECs.
Water management within the gas diffusion layer (GDL) plays an important role in the performance of the proton exchange membrane fuel cell (PEMFC) and its reliability. The compression of the gas diffusion layer during fabrication and assembly has a significant impact on the mass transport, and the porosity gradient design of the gas diffusion layer is an essential way to improve water management. In this paper, the two-dimensional lattice Boltzmann method (LBM) is applied to investigate the two-phase behavior in gas diffusion layers with different porosity gradients under compression. Compression results in an increase in flow resistance below the ribs, prompting the appearance of the flow path of liquid water below the channel, and liquid water breaks through to the channel more quickly. GDLs with linear, multilayer, and inverted V-shaped porosity distributions with an overall porosity of 0.78 are generated to evaluate the effect of porosity gradients on the liquid water transport. The liquid water saturation values within the linear and multilayer GDLs are significantly reduced compared to that of the GDL with uniform porosity, but the liquid water within the inverted V-shaped GDL accumulates in the middle region and is more likely to cause flooding.
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