Junjie Chen

Popular packing materials used in HDH systems.

High-vacuum multilayer insulation (MLI) is critical for efficient storage and transport of cryogenic liquids, yet its performance severely degrades upon vacuum loss, posing safety risks, especially with condensable gases like CH4. Current research lacks systematic evaluation of industrial-grade MLI under such failure scenarios. This study experimentally investigated the thermal shock resistance of a novel composite MLI structure, incorporating plant fiber paper and aluminum foil, compared to conventional glass‐fiber‐based MLI. Using a custom cryogenic vessel equipped with vacuum, data acquisition, and gas intrusion systems, sudden vacuum failure with both CH4 and air were tested. Results showed that CH4 ingress caused a rapid, peak mass flow rate approximately 14 times higher than air, accompanied by transient temperature fluctuations due to CH4 condensation/re-vaporization. The novel structure reduced the peak evaporation rate by 7.64% compared to conventional MLI under air intrusion, demonstrating superior thermal buffering. This work can provide essential experimental data and analysis on heat‐transfer mechanisms during vacuum loss, offering practical guidelines for designing safer cryogenic storage systems handling condensable gases.

The vacuum failure of high-vacuum multilayer insulation (MLI) in cryogenic storage vessels presents a major safety risk, especially when condensable gases like CH4 intrude, a scenario insufficiently addressed in prior research focused on aerospace applications. To bridge this gap, this study developed and evaluated a novel aerogel-composite MLI structure, comparing its thermal-shock resistance. Experiments were conducted on a 135 L cryogenic vessel using liquid nitrogen. The gas evaporation rate and multilayer temperature profiles were measured to calculate the post-failure heat leakage and analyze the underlying heat transfer mechanisms. Experimental results demonstrated that CH4 ingress induced a drastically more severe thermal response than air, with a peak heat flux density of 1266.98 W/m2 (approximately five times higher), while a corresponding outer wall temperature dropped 17 times greater. The thermal response for CH4 exhibited a distinct three-phase evolution and a later recovery trend, driven by complex phase-change dynamics including condensation and freezing within the insulation. The comparison results showed that the insulation effect of the designed material had been improved by 23.45% compared with the conventional structure. The relevant experimental phenomena can provide valuable guidance for the safety design and risk assessment of cryogenic storage and transportation equipment handling condensable gases.

To maximize the energy effectiveness and minimize the pressure drop of the packed bed humidifier filled with corrugated wire mesh packing, potentially, multi-objective optimization is implemented based on response surface method and genetic programming. One geometric parameter and four thermodynamic parameters are considered as the design variables, and the objective functions include energy effectiveness and pressure drop in Box-Behnken design. Then a reliable quadratic regression model of objective function is formed based on the 46 groups of experimental design schemes. The analysis results of variance indicate that pressure drop model shows a higher accuracy compared with energy effectiveness model. It is found that liquid-gas ratio, combination of liquid-gas ratio and inlet air temperature are respectively the most significant factors for energy effectiveness among the independent and interactive parameters, while it is specific surface area and combination of liquid-gas ratio and specific surface area for pressure drop, according to the Prob > F values. Besides, an optimal parameter group is obtained more quickly and several Pareto-optimal points are given after natural evolution. In addition, the actual optimal energy effectiveness of 0.94 and pressure drop of 0.34 Pa are simultaneously gained via introducing the optimal parameter group into the established mathematical models. Furthermore, it is also demonstrated that energy effectiveness improves by 40.30% and pressure drop reduces by 66.99%, respectively, compared with the best results before optimization.

The separator with inner channels is designed to solve the re-entrainment phenomenon of particles, improving the separation efficiency. Firstly, experiments are established to compare the separation efficiency and pressure drop between ordinary separators and ones with inner channels. Secondly, the Reynolds Stress model and the Euler–Euler model are applied to simulate the turbulence and particle flow, respectively. Lastly, the Population Balance model (PBM) is used to define different distributions of particle diameter by initial moments. The research results demonstrate that the inner channels can improve separation efficiency significantly because they can restrain the re-entrainment phenomenon. The separation efficiency of the design and the conventional ones is 97% and 90%, respectively, but the pressure drop increases by 39 Pa in this structure. Simultaneously, this structure has a lower tangential velocity compared with the separator without inner channels, reducing particle collisions with the wall. Radial pressure differences are also declined in the structures with inner channels, leading to a decreased pressure gradient force. Furthermore, the sixth moment has a larger median particle size, while the particle size distribution at the outlet of the separator is similar to that at the inlet via the PBM. And the maximum separation efficiency of the design and ordinary ones is 99% and 80%, respectively. The characteristics listed above can help with efficient separator design.

This paper aims to introduce thermal energy storage technology into a solar-powered dual-packed bed desalination system. By prehesdating and reserving seawater during the daytime and utilizing it at night, the integrated desalination system with innovative configuration can achieve freshwater and electricity combined generation and particularly realize the continuous operations for water production. The detailed mathematical model is established, and the corresponding parametric analyses are executed with various operating situations. The simulation results show that with the rise of top temperature, the performance indicators of the system, gained-output-ratio (GOR), and water productivity, reach the maximum value at the MFRR corresponding to the balance condition of dehumidifier, while the power generation of photovoltaic/thermal (PV/T) reaches minimum value under different incident conditions. It is summarized that the balance condition also represents the upper limit of air compensation capability and the “turning point” of air temperature, which can be enhanced by raising the top temperature of the system. Furthermore, the integrated system outperforms other HDH configurations in prior research, demonstrating the feasibility and superiority of the present continuous water-producing HDH system supported by thermal energy storage.

In this paper, an axial flow cyclone separator is employed to separate the droplets entrained in saturated steam turbine. The Eulerian–Eulerian approach and the Reynolds stress model are combined in numerical simulation. Then, the effects from the vane exit angle and the length of separation section on the separation performance are investigated, respectively. The distributions of pressure and velocity in the cyclone are presented in detail to describe the characteristics of flow field. The results demonstrate that the separation efficiency could be effectively elevated to 95% either by reducing vane exit angle or by increasing the inlet-velocity. In addition, the promotion brought by reducing the vane exit angle is larger than that of increasing inlet-velocity once comprehensively assessing pressure drop and separation efficiency. Furthermore, it is found that the designed the length of separation section should not be too short to reduce the steam leakage ratio, considering that the steam is flowed into the saturated steam turbine. The leakage ratio would decrease by 15% as the aspect ratio of separation section increases from 1.5 to 3.5. The improvement of separation efficiency can effectively reduce the damage of the steam turbine and improve its operational safety.

This paper proposes a piezoelectric energy harvester based on non-homogeneous beam, which is employed to capture wind energy by galloping. A distributed parameter model of piezoelectric energy harvester with the nonuniformity of cantilever beam is developed. The quasi steady state approximation is used to simulate the fluid force. The model is verified by the experimental results reported previously. The influences of load resistance, the position of piezoelectric patch, and the size of beam on the output power are studied. Finally, a set of optimization parameters are generated to study the performance of the energy harvester. The results show that compared with rectangular beam, the output power of piezoelectric energy harvester with non-homogeneous beam can be increased by 32%.