A new method for the investigation of fluid-fluid mass transfer—II. Mass transfer in liquid-liquid systems

A new dynamic electrochemical method for the determination of liquid-liquid mass-transfer coefficients in a stirred cell and in a mixer cell is described. Current transients are recorded for different flow conditions and evaluated applying a non-linear regression analysis. The resulting mass-transfer coefficients correlate linearly with the stirring rate but the mean values over a long time period are considerably low. The extent of the investigated initial time dependence of the mass-transfer coefficient decreases with increasing electrolyte concentration.     

Microstructure and Property of HD Die Steel With Unsmoothed Surface With Various Laser Parameters

The reticulate unsmoothed surfaces on HD die steel, which imitate the surface of soil-burrowing animals （such as the dung beetle, earthworm, pangolin, and ant） are produced with various laser parameters. The characteristics （including width, depth, area ratio, and volume）, microstructure, and hardness of the unsmoothed units are studied. At the same time, the wear resistance of the material with an unsmoothed surface is measured. The results show that the width and volume of the unit increase, the microstructure becomes coarser, the hardness decreases, and the wear resistance improves with the increase of the current intensity and pulse duration within a certain range. However, there is little difference between the extent to which the wear resistance of the material increases and the unsmoothed surface, when the current intensity and pulse duration increase to some extent. The wear resistance of the unsmoothed material under 300 A or 20 ms is better in the experiments. The improving extent of the wear resistance lies in a combination of the characteristics, microstructure, and hardness of the unsmoothed unit. An unsmoothed material with better properties can be processed if the laser parameters are well matched.     

Optimal planning for industrial park-integrated energy system with hydrogen energy industry chain

Establishing an industrial park-integrated energy system (IN-IES) is an effective way to reduce carbon emission, reduce energy supply cost and improve system flexibility. However, the modeling of hydrogen storage in traditional IN-IES is relatively rough. In order to solve this problem, an IN-IES with hydrogen energy industry chain (HEIC) is proposed in this paper. Hydrogen production, transportation, and storage technologies are applied in HEIC. Firstly, a novel long-term hydrogen storage model considering different time steps is presented. Secondly, hydrogen compressor models considering different pressure ratios are further employed. On this basis, the impact of the HEIC on the planning and operation results of IN-IES is studied. Finally, the superiority and the effectiveness of the proposed model and planning method are verified by simulation cases.     

Numerical analysis on the anode active thickness using quasi-three-dimensional solid oxide fuel cell model

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Novel and high-performance (La,Sr)MnO3 based composite cathodes for intermediate-temperature solid oxide fuel cells

The rapid decrease of the electrocatalytic activity at low temperature (<700 ℃) limits the popularization and application of the classical cathode material LSM (Sr doped LaMnO₃) in SOFC. Herein, we report that the introduction of CBO (CuBi₂O₄) oxide could not only reduce the sintering temperature of LSM-based cathode, but also significantly improves its electrochemical performance at intermediate temperature range of 500–700 ℃. The polarization resistance (R_p) of LSM-CBO20 (including 20 wt. % CBO) composite cathode on GDC electrolyte is only 0.13 Ω cm² at 700 ℃, which is significantly lower than the LSM cathode. The study found that the quite promoted oxygen surface exchange kinetics and catalytic activity of CBO, and the much reduced sintering temperature of the composite cathode contribute to the dramatic decrease of R_p. In addition, when Gd_0.1Ce_0.9O_1.95 (GDC) is introduced, the polarization resistance is further reduced to 0.11 Ω cm² at 700 ℃. The maximum power density of the single cell with LSMGDC-CBO20 triadic phase cathode reaches to 1460 mW cm^-2 at 700 ℃. The present study demonstrates that introducing CBO is an effective and promising approach to improve the electrochemical performance of conventional LSM-based cathode at reduced temperatures.     

Structure,dielectric, and ferroelectric properties of (1-x)Bi0.5Na0.5TiO3 – X K0.5Na0.5NbO3 (0 ≤ x ≤ 0.1) solid solution

The correlation of the phase structure, dielectric, and ferroelectric properties of lead-free (1-x)(Na_0.5Bi_0.5)TiO₃–xK_0.5Na_0.5NbO₃ (NBTKNx) (0 = x ≤ 0.1) polycrystalline ceramics, fabricated via a solid state reaction technique, were investigated. The Rietveld refinement allowed identifying the crystallographic transformation from a rhombohedral to a coexisting rhombohedral-tetragonal or tetragonal long range-ordered ferroelectric (FE) phase. The dielectric investigations showed an increase of the dielectric diffuseness (1.53 = γ ≤ 1.73) and a clear shift of the depolarization temperature (T_d) to a lower temperature while increasing substitution. More importantly, the lattice disorder also generated a plateau-like dielectric anomaly, leading to a thermally stable ϵ_r ∼2859 ± 20% (120–500 °C) and ∼3112 ± 10% (120–420 °C) for x = 0.075 and 0.1 samples, respectively. At room temperature (RT), Raman spectroscopy investigations revealed a downshift of the frequencies as a function of the composition with an inhomogeneous broadening of the Raman lines. On heating, Raman spectra showed changes in the region where the dielectric transitions are observed. Moreover, the composition dependence of the current peaks in the I-E loops confirmed the occurrence of a phase transition from a non-ergodic polar phase to an ergodic weakly polar after the applying of an electric field of 60 kV/cm⁻¹.     

Experimental investigation on dyeing wastewater treatment and by-product hydrogen with a reverse electrodialysis flocculator

Hydrogen production and dye degradation can be achieved simultaneously in a hybrid system of reverse electrodialysis（RED）and electrocoagulation (EC), using current derived from the salinity gradient energy. Under the current, Fe electrode is used as the anode to produce Fe²⁺(subsequently oxidized to Fe³⁺) which combines with OH⁻ produced from the cathode to remove the dyes, while the hydrogen gas produced by the cathode is collected by a hydrogen collection device. The experiments are carried out to investigate the effects of different initial concentrations, pH, currents, electrode rinse solution (ERS) flow rates and the addition of chlorine on the degradation rate and hydrogen production. The results indicate that the degradation rate and hydrogen production could reach 98.3% and 150 m h⁻¹ at alkaline condition (pH = 11) and acidic condition (pH = 3) respectively, with a current of 0.4 A. The degradation rate and hydrogen production increase significantly with an increase in current.     

Ultradurable Omni-Liquid-Repellent Smart Window as a High-Performance Wettability/Transparency Manipulator Enabled via Laser-Writing Magnetism-Actuated Microshutters

Slippery liquid-infused porous surfaces (SLIPS) derived smart windows (SWs) that dynamically fine-tune the solar spectrum are promising candidates for alleviating the global energy crisis, especially for dim rainy climates. Unfortunately, the inferior durability, high energy-consumption, and slow tune-responsivity over SLIPS-based SWs greatly hinder their practical usage. Reported is an ultrarobust omni-liquid-repellent magnetism-actuated reconfigurable microshutters (OLR-MARS) via integrating a femtosecond laser ablation and soft-lithography technique. By alternately loading/discharging a remote magnet, OLR-MARS can be reversibly switched between a transparent mode and an opaque mode within 0.03 s, which is far sensitive than the previously-reported SWs. Simultaneously, OLR-MARS can harness the surface liquids between a slippery state (the sliding angle of ≈15^o) and a sticky one (pinning at a tilt angle of 90^o). Significantly, owing to its all-solid-state merit, OLR-MARS demonstrates good longevity even when subjected to the raindrops impact above 1000 cycles. Results indicate dual switching over the interfacial hydrodynamics and optics. Last but not least, leveraging the optimized OLR-MARS, encryption-decryption, thermal management, and an angle-dependent privacy-screen is deployed. Current novel OLR-MARS with robust durability, fast responsivity, and energy-free advantages holds promising potential in self-cleaning smart windows, energy-saving buildings, antivoyeurism, etc.     

Energy saving analysis and thermal performance evaluation of a hydrogen-enriched natural gas-fired condensing boiler

Hydrogen-enriched natural gas (HENG) has attracted widespread attention due to its lower pollutant emissions and industrial decarbonization in the past decades. HENG combustion boosts the water content in the flue gas, which is highly favorable for condensing boilers to recover additional latent heat. The energy saving and thermal performance of a condensing boiler burning HENG were evaluated at a constant heat load of 2.8 MW in this study. The variations in combustion products and boiler efficiency were investigated based on the material balance and energy conservation. The heat transfer calculations were employed to evaluate the thermal performance of boiler heating surfaces. The energy recovery performance of the condenser was assessed via a thermal design method. Results show that H₂ enrichment enhances the radiation intensity of the flame due to the incremental triatomic gases with higher emissivity in the furnace. The heat absorption ratio increases with H₂ enrichment in the radiative heating surface, while it shows a reverse tendency in the convective heating surface. The condensing boiler efficiency based on lower heating value increases from 101.83% to 110.60%, the total heat transfer rate of the condenser increases from 2.77 × 10⁵ W to 4.61 × 10⁵ W, and the total area required decreases from 46.45 m² to 42.16 m², as the H₂ enriches from 0 to 100% under the exhaust flue gas temperature of 318 K. Although the amount of recoverable heat in the exhaust flue gas increases considerably after H₂ blending, the original condenser with natural gas as the designed fuel could meet the requirements of the heat recovery for HENG without increasing the extra heating surface. When the H₂ fraction is enriched from 0 to 100%, CO₂ emission intensity drops from 6.05 × 10⁻⁸ kg J⁻¹ to 0. This work may offer some theoretical references for the application and generalization of HENG condensing boilers.