The effects of different modeling and solving approaches on the simulation of a steam ejector have been investigated with the computational fluid dynamics (CFD) technique. The four most frequently used and recommended turbulence models (standard k-ε, RNG k-ε, realizable k-ε and SST k-ω), two near-wall treatments (standard wall function and enhanced wall treatment), two solvers (pressure- and density-based solvers) and two spatial discretization schemes ( the second-order upwind scheme and the quadratic upstream interpolation for convective kinematics (QUICK) of the convection term have been tested and compared for a supersonic steam ejector under the same conditions as experimental data. In total, more than 185 cases of 17 different modeling and solving approaches have been carried out in this work. The simulation results from the pressure-based solver (PBS) are slightly closer to the experimental data than those from the density-based solver (DBS) and are thus utilized in the subsequent simulations. When a high-density mesh with y⁺ < 1 is used, the SST k-ω model can obtain the best predictions of the maximum entrainment ratio (ER) and an adequate prediction of the critical back pressure (CBP), while the realizable k-ε model with the enhanced wall treatment can obtain the best prediction of the CBP and an adequate prediction of the ER. When the standard wall function is used with the three k-ε models, the realizable k-ε model can obtain the best predictions of the maximum ER, and the three k-ε models can gain the same CBP value. For a steam ejector with recirculation inside the diffuser, the realizable k-ε model or the enhanced wall treatment is recommended for adoption in the modeling approach. When the spatial discretization scheme of the convection term changes from a second-order upwind scheme to a QUICK scheme, the effect can be ignored for the maximum ER calculation, while only the CBP value from the standard k-ε model with the standard wall function is reduced by 2.13%. The calculation deviation of the ER between the two schemes increases with the back pressure at the unchoked flow region, especially when the standard k-ε model is adopted. The realizable k-ε model with the two wall treatments and the SST k-ω model is recommended, while the standard k-ε is more sensitive to the near-wall treatment and the spatial discretization scheme and is not recommended for an ejector simulation.

To promote the development and application of the liquid–gas jet pump (LGJP), the research status of its design theory, internal flow mechanism, structural optimization and practical application are reviewed. The development history of the LGJP is briefly reviewed, the latest research and application progress of the LGJP is introduced, and the pulse-type of LGJP, especially the centrifugal jet vacuum pump (CJVP), is emphatically discussed. The research and development direction of the LGJP is analyzed and proposed: CFD will be more deeply applied to the mechanism research and performance improvement of the LGJP; the diversity and heterogeneity of the fluid medium and its influence on the internal flow mechanism are the research highlights of the LGJP; it is urgent to study the gas–liquid two-phase flow and pumping mechanism inside the pulsed liquid–gas jet pump (PLGJP), especially the CJVP.

An experimental study is conducted to investigate the effects of different operating parameters on the performance of liquid–gas jet pumps. A square nozzle with an area ratio of 2.25 is designed for the liquid–gas jet pump, and an experimental setup for the liquid–gas jet pump system is constructed. By varying parameters such as inlet flow rate, temperature, and inlet pressure, the variations in the pumping capacity and pumping ratio of the system are studied. The performance of liquid–gas jet pumps with square nozzles and traditional circular nozzles under the same working conditions was compared through experimental data. Explore the performance advantages and disadvantages of liquid–gas jet pumps with different shaped nozzles under the same working conditions. The experimental results indicate that as the inlet flow rate of the liquid–gas jet pump increases, the pumping capacity of the system increases, leading to an increase in the pumping ratio. The operational efficiency slightly decreases with a rise in the working water flow rate. The pumping ratio of the system increases with an increase in the inlet pressure, reaching a peak value of around 4.0 when the inlet valve is fully open. Inlet pressure significantly affects the efficiency of the liquid–gas jet pump, with the highest efficiency point achieved at Pa (inlet air pressure) = 60 kPa, reaching an operational efficiency of 42.48%. When Pa exceeds 70 kPa, the operational efficiency rapidly declines. Comparing the performance of square and circular nozzle liquid–gas jet pumps under the same operating conditions, the performance of the square nozzle liquid–gas jet pump outperforms that of the circular nozzle counterpart. The pumping system’s performance decreases continuously with an increase in the working liquid temperature; however, the decline in pumping performance becomes gradual after exceeding 40 °C. As the water level rises, both the pumping capacity and pumping ratio of the system increase. After the liquid level reaches 40 cm, the changes in the pumping system’s performance become less pronounced.

Computational fluid dynamics (CFD) is adopted to calculate and analyze the performance and separation mechanism of a steam-water separation equipment for a pressurized water reactor (PWR) steam generator. The steam-water two-phase flow is simulated by the Euler two-fluid model, and several representative water droplet diameters are selected among 50 to 400 μm. The influence mechanism of water droplet diameter on the performance is investigated by analyzing the flow parameters such as phase volume fraction, velocity, and turbulent kinetic energy. The results show that the integrated calculation and analysis of the separation equipment can more truly reflect the flow state between the separators, improving the reliability of the performance prediction and mechanism analysis. With the increase in water droplet diameter, the separation efficiency of the separation equipment and each separator gradually increases, the outlet wetness gradually decreases, and the pressure loss first decreases and then stabilizes. When 400 μm is taken as the characteristic value of the actual droplet diameter distribution at the inlet of the separation equipment, the performance prediction is more accurate, the pressure loss of each separator is relatively close, and the pressure loss of the primary separator is less affected by the droplet diameter and smaller than that of the swirl-vane primary separator, which is conducive to achieving a higher circulation ratio (CR). Re-entrainment occurs at the perforations of the primary separator and the outlet of the secondary separator, and the corresponding structure is suggested to be optimized to further improve separation efficiency of the separation equipment.

Printed Circuit Heat Exchangers (PCHEs) are considered an excellent alternative for the main cryogenic heat exchanger of Floating Liquefied Natural Gas (FLNG) facilities due to their compact structure and strong heat transfer performance. However, it is unclear how to configure the geometry of the PCHE channels to achieve its optimal performance in the trans-critical liquefaction process of natural gas (NG), which is critical for the main heat exchanger. In this paper, we numerically studied the thermal-hydraulic characteristics of PCHEs with different channel types under the specified condition. The results elucidate that all channels have an enhancement of heat transfer near the pseudo-critical point of NG. All the wavy channels could improve the heat transfer performance of PCHEs, where the trapezoidal channel achieves the largest promotion. Compared with the straight channel, the local heat transfer coefficient could be increased by up to 53% in the trapezoidal channel. Additionally, vortex appeared at the bends of the wavy channels, which greatly increase the local friction loss. Among several channels, the total pressure drop of zigzag, fillet and the sinusoidal channel was almost the same, while that of the trapezoidal channel was the largest. Furthermore, we compared the comprehensive performance of different types of channels and found that the benefit of heat transfer enhancement could not offset the penalty of flow deterioration. Our work provides important guidance for the design of PCHEs employed in FLNG.

The rapid development of wearable electronics highlights the urgence to develop the portable energy harvester with excellent output performance, comfortability, and sustainability. This work designs an electromagnetic walking energy harvester based on water turbine that can be embedded in shoes with good comfortability. Its working principle is that the walking generated pressure energy drives a miniature hydraulic turbine to output electricity. Experimental results show that an average power of 300 and 180 mW can be produced at heel and toe, respectively, when a man of 80 kg walks at a speed of 1.8 m s−1. This power output exceeds the piezoelectric, triboelectric, and electromagnetic walking energy harvesters reported in the past. Additionally, the simpler structure endows it better comfortability as compared with the electrostatic capacitances. Computational fluid dynamics simulations provide a further insight that the efficiency of turbine can reach 13.5% by optimizing parameters of blade number and outlet flow ratio. Finally, user real-time positioning and trajectory recording are successfully demonstrated via a wearable GPS means Global Positioning System module powered by the harvester. Due to the combination of high output performance, simple structure and low discomfort, the water turbine based walking energy harvester will provide a wide application potential in wearable devices.