Cyclic uniaxial stress-controlled ratcheting behaviors of 35CrMo structural steel were investigated at 500 °C. The effects of stressing rates and stress amplitudes were discussed in detail. Results present that the accumulated ratcheting strain increases with the increment of stress amplitude, while decreases with the reduction of stress rate at elevated temperature. Moreover, the ratcheting evolution curves with increasing number of cycles are similar to traditional static creep curves, and can be mainly divided into three stages. Especially, the ratcheting strain rate during the steady stage can be easily obtained to estimate the ratcheting or shakedown behavior. Furthermore, the steady ratcheting strain rate significantly decreases with increasing the stressing rate when the stressing rate is relatively slow. However, when the applied stressing rate is greater than a critical value, such as ≥ 2·5 MPa s⁻¹ for = 200 MPa and ≥ 25 MPa s⁻¹ for σ_max = 500 MPa, the effect of stressing rate has little effect on the cyclic ratcheting strain rate.

In order to promote the application of electrochemical water softening technology in industrial circulating cooling water systems, electric field type, cathode structure and solution residence time are selected for optimization analysis of an electrochemical water softening device. The experimental results show that the water softening performance per unit area of mesh cathode is better than that of a plate cathode. In addition, the softening amount per unit area of the mesh cathode can be further increased when the high-frequency (HF) power supply is applied. When the HF power supply is applied, the softening amount per unit area is 158.58 g/m2·h−1 more than when the direct current power supply is applied. In order to explore the growth mechanism of calcium carbonate, micro-analysis technology and high-speed bubble photography technology are used. The results show that the bubbles escape along the longitudinal direction of the electrode plate, and the main growth direction of calcium carbonate growth is consistent with the escape direction of the bubble; that is, the bubbles grow along the longitudinal direction of the electrode plate. The special structure of the diamond-shaped mesh cathode facilitates the growth of calcium carbonate crystals.

Heat exchangers are widely used in petrochemical and other industries. Improving the efficiency of heat exchangers to increase energy utilization is crucial. Passive enhanced heat transfer technology is widely studied in heat exchanger research due to its low energy consumption and simple operation. Helical baffle–corrugated tube heat exchangers have not been extensively studied as a promising new class of these devices. This paper investigates the key structural parameters of a helical baffle-corrugated heat exchanger through numerical simulation. This study focuses on the factors affecting heat transfer and flow resistance performance. The results show that reducing the helical angle from 28.42° to 10.81° increases the total heat transfer coefficient by approximately 20%. The overall performance of the heat exchanger is evaluated using the efficiency evaluation coefficient (EEC). Optimal levels of each structural factor are determined for different working conditions based on this evaluation.

To analyze the effect of flow characteristics on electrochemical water softening, characteristics of flow fields in the vicinity of vertical plate electrodes in a bench-scale electrolysis cell for electrochemical water softening were visualized using particle image velocimetry technology, and the hardness drop values under different process conditions were measured. Properly increasing the current density or reducing the electrode spacing can increase the average flow velocity in the electrode gap. Excessive current density will cause bubble accumulation, form a bubble vortex, interfere with the orderly flow of surrounding liquid and reduce mass transfer efficiency. When the electrode spacing is 120 mm, the highest water softening efficiency measured at the current density of 60 A/m2 is 16.56%. When the current density is 50 A/m2, the highest average speed measured at the electrode spacing of 60 mm is 0.00169 m/s, but the highest water softening efficiency measured at the electrode spacing of 90 mm is 23.3%.The circulation efficiency in the electrode gap of a semi-closed structure is lower than that of a free convection structure. The behavior of bubbles is the key to flow and mass transfer. It is important to consider its influence on bubble behavior when optimizing electrochemical parameters.

Electrochemical water treatment technology can be used for hard water softening, but its removal efficiency and energy consumption problems hinder its application. The effects of electrolysis voltage and cathode materials on efficiency, energy consumption and scale crystal form of electrochemical water treatment technology were studied experimentally. The experimental results show that electrochemical water treatment can effectively remove more than 40% of the TDS (total dissolved solids) in the influent. The electrolysis voltage has a great influence on the removal rate of hardness ions. The optimum electrolytic voltage for the titanium plate cathode is 25 V. At this electrolytic voltage, the treatment capacity of the titanium plate cathode is 16% higher than that of the copper plate cathode, and the energy consumption is 16% lower than that of the copper plate. Titanium plates are more efficient than copper plates and consume less energy. The effects of electrochemical water treatment on the scale crystal form were investigated by SEM (scanning electron microscopy) and XRD (X-ray diffraction). Electrochemical water treatment increases the mass fraction of aragonite in the calcium carbonate scale and changed the microscopic surface structure of calcium carbonate scale.