The maldistribution of fluid flow through multi-channels is a critical issue encountered in many areas, such as multi-channel heat exchangers, electronic device cooling, refrigeration and cryogenic devices, air separation and the petrochemical industry. In this paper, the uniformity of flow distribution in a printed circuit heat exchanger (PCHE) is investigated. The flow distribution and resistance characteristics of a PCHE plate are studied with numerical models under different flow distribution cases. The results show that the sudden change in the angle of the fluid at the inlet of the channel can be greatly reduced by using a spreader plate with an equal inner and outer radius. The flow separation of the fluid at the inlet of the channel can also be weakened and the imbalance of flow distribution in the channel can be reduced. Therefore, the flow uniformity can be improved and the pressure loss between the inlet and outlet of PCHEs can be reduced. The flow maldistribution in each PCHE channel can be reduced to ± 0.2%, and the average flow maldistribution in all PCHE channels can be reduced to less than 5% when the number of manifolds reaches nine. The numerical simulation of fluid flow distribution can provide guidance for the subsequent research and the design and development of multi-channel heat exchangers. In summary, the symmetry of the fluid flow in multi-channels for PCHE was analyzed in this work. This work presents the frequently encountered problem of maldistribution of fluid flow in engineering, and the performance promotion leads to symmetrical aspects in both the structure and the physical process.

The two-phase ejector is a simple and compact pressure boosting device and widely used in ejector steam-generator water feeding systems and core emergency cooling systems. The direct contact condensation of water and steam is the key process of a two-phase ejector. Usually, the high-temperature and high-pressure steam will inevitably induce non-condensable gases. The existence of non-condensable gases will reduce the condensation heat transfer rate between steam and water, and harm the equipment. This study carried out 3D numerical simulations of a two-phase ejector based on an inhomogeneous multiphase model. The steam inlet pressure and the non-condensable gas mass fraction rang in 0.6–2.9 MPa and 1–10%, respectively. The heat and mass transfer characteristics were analyzed under different conditions. The results show that the heat transfer coefficient and plume penetration length increased with the steam inlet pressure. Non-condensable gas prevents direct contact condensation between the steam and water. The non-condensable gas mass fraction rises from 1% to 10%, the heat transfer between steam and water deteriorates, and leads to a lower heat transfer coefficient.

The huge amount of energy generated by cavitation in liquids can be used to achieve more ecologically friendly and efficient removal of algae. Jet pumps readily induce cavitation owing to their tapering section structure and thus have the potential to be used as jet cavitation reactors (JCRs) to achieve hydrodynamic cavitation and algal removal under suitable pressure conditions. In this paper, we examine the cavitation characteristics of a JCR at different working fluid temperatures, using large eddy simulation. The vortex structure created by high-speed jets at the nozzle of the JCR is continuous and orderly, whereas the downstream vortex structure becomes chaotic and fragmented under the actions of flow mixing and bubble development. An increase in water temperature can reduce vorticity. As the water temperature rises, the cavitation number decreases, the total cavity volume increases, and cavitation changes from an unstable to a stable limit state. When cavitation is in its unstable limit state, the total bubble volume exhibits quasi-periodic changes and the cavitation cloud pulsates strongly, while when cavitation is in its stable limit state, cavitation cloud pulsation is seen only at the outlet.

Significant harm from heat has become a key restriction for deep metal mining with increasing mining depth. This paper proposes a refrigeration ventilation system for deep metal mines combined with an existing air cycling system and builds an experimental platform with six stope simulation boxes. Using the heat current method and the driving-resistance balance relationship, the heat transfer and flow constraints of the system were constructed. An artificial neural network was used to establish models of heat exchangers and refrigerators with historical experimental data. Combining the models of the system and stope simulation box, an algorithm that iterates the water outlet temperature of the evaporator and condenser of the refrigerator was proposed to design the coupled simulation model. The heat balance analysis and comparison of the air outlet temperatures of the stope, as well as the heat transfer rates of the heat exchangers with the experimental data, validated the coupled simulation model. Additionally, the effects of cooling fans and the air inlet temperature of the cooling tower were discussed, which provided a powerful modelling method for the coupled model of a refrigeration ventilation system, helps to reduce energy consumption, and improves the sustainability of mining production.

A fixed pad seawater-lubricated bearing has been designed according to the structure parameters and loading requirements of axial flow pump. Water film lubrication model was built and 3-D simulations were performed for water-lubricated bearings. The pressure distribution inside the bearing predicted by simulations agrees very well with the theoretical predictions. The formation mechanism of dynamic pressure inside water–lubricated bearing was revealed. Then the pressure distribution characteristics were analyzed. It was found that the loading capacity would increase linearly with the angular speed, and the designed bearing could meet the loading requirements even at the lowest angular speed of the given axial flow pump.