This review paper provides an overview of recent advances in computational fluid dynamics (CFD) simulations of ejector pumps for vacuum generation. It examines various turbulence models, multiphase flow approaches, and numerical techniques employed to capture complex flow phenomena like shock waves, mixing, phase transitions, and heat/mass transfer. Emphasis is placed on the comprehensive assessment of flow characteristics within ejectors, including condensation effects such as nucleation, droplet growth, and non-equilibrium conditions. This review highlights efforts in optimizing ejector geometries and operating parameters to enhance the entrainment ratio, a crucial performance metric for ejectors. The studies reviewed encompass diverse working fluids, flow regimes, and geometric configurations, underscoring the significance of ejector technology across various industries. While substantial progress has been made in developing advanced simulation techniques, several challenges persist, including accurate modeling of real gas behavior, phase change kinetics, and coupled heat/mass transfer phenomena. Future research efforts should focus on developing robust multiphase models, implementing advanced turbulence modeling techniques, integrating machine learning-based optimization methods, and exploring novel ejector configurations for emerging applications.

This paper presents and discusses the results of the “2024 International Computational Fluid Dynamics Challenge on the long-range indoor dispersion of pathogen-laden aerosols” aimed at assessing the ability of different computational codes and turbulence models to reproduce the dispersion of particles produced by a turbulent natural convection flow enclosed in a room sized cubical cavity. A total of 12 research groups from ten different countries have conducted 15 simulations of the same flow configuration by solving the Reynolds averaged Navier–Stokes (RANS) equations, the unsteady Reynolds averaged Navier–Stokes (URANS) equations or using scale adaptive simulations (SAS), large-eddy simulations (LES), or hybrid (URANS-LES) techniques. Results for the velocity field and the particle dispersion provided by the different simulations are compared extensively, including the reference results provided by a direct numerical simulation (DNS). In general, LES and hybrid methods reproduce the time-averaged flow field correctly, the spatial distribution of the turbulence kinetic energy, and the particle dispersion. The performance of SAS is similar to that of LES and hybrid methods while the predictions of the RANS and URANS simulations exhibit larger deviations with respect to DNS. In general, the particle dispersion is better reproduced by simulations that capture correctly the spatial distribution of the turbulence kinetic energy.

This review paper provides an overview of recent advances in computational fluid dynamics (CFD) simulations of ejector pumps for vacuum generation. It examines various turbulence models, multiphase flow approaches, and numerical techniques employed to capture complex flow phenomena like shock waves, mixing, phase transitions, and heat/mass transfer. Emphasis is placed on comprehensive assessment of flow characteristics within ejectors, including condensation effects such as nucleation, droplet growth, and non-equilibrium conditions. The review highlights efforts in optimizing ejector geometries and operating parameters to enhance the entrainment ratio, a crucial performance metric for ejectors. The studies reviewed encompass diverse working fluids, flow regimes, and geometric configurations, underscoring the significance of ejector technology across various industries. While substantial progress has been made in developing advanced simulation techniques, several challenges persist, including accurate modeling of real gas behavior, phase change kinetics, and coupled heat/mass transfer phenomena. Future research efforts should focus on developing robust multiphase models, implementing advanced turbulence modeling techniques, integrating machine learning based optimization methods, and exploring novel ejector configurations for emerging applications.

This work presents a study on the calculation of transmittance in an Air Handling Unit (AHU) through three methods: theoretical estimation, experimental approach and numerical simulations. First, a theoretical estimation based on simplified models of heat and mass transfer in the AHU was employed. In addition, experimental tests were carried out in a real AHU under controlled conditions, obtaining temperature measurements inside and outside the unit. These data were used to calculate the transmittance using predefined formulas. Finally, numerical simulations were performed on specific sections of the AHU and on a global model, with and without radiation considering its influence. The simulations provided detailed results on the flow behaviour and temperature distribution. The results obtained were compared and analysed to assess the accuracy and applicability of the three methods. This research contributes to the knowledge and understanding of transmittance in AHUs, providing valuable information for the design and optimisation of Heating, Ventilation, and Air Conditioning (HVAC) systems.

This work presents a study on the calculation of transmittance in an air handling unit (AHU) through three methods. A semi-empirical estimation based on simplified models of heat and mass transfer has been used. In addition, experimental tests were carried out in a real AHU under controlled conditions. The measured temperature inside and outside the AHU were used to calculate the transmittance. Finally, numerical simulations were performed on specific sections of the AHU and on a global model, with and without radiation. The simulations provided detailed results on the flow behavior and temperature distribution. The results were compared and analyzed to assess the accuracy and applicability of the three methods. The heat transfer obtained with the semi-empirical method is 38% larger than that obtained with the experimental measurement, in contrast with the 8% of difference observed with numerical simulations. It is revealed that radiation, and thus the emissivity of surfaces, plays an important role in heat transfer of the AHU. This research contributes to the knowledge and understanding of transmittance in AHUs, providing valuable information for the design and optimization of heating, ventilation, and air conditioning (HVAC) systems.

A water–steam ejector can be used for steam exhausting in some equipment, such as sterilization systems in hospital facilities. In this type of ejector, a water jet in the center is used to entrain and transport steam from the sterilization chamber. The performance of the ejector, which is a function of the pressure in the sterilization chamber and the temperature of the water, is crucial for the reduction in water and energy consumption. The numerical simulation of this type of device is challenging because of the mass, momentum and energy exchange between the phases. In this study, numerical simulations of an axisymmetrical model of a water–steam ejector considering mixing and heat and mass transfer by condensation are shown. The Euler–Euler method with OpenFOAM v2312 was used. The influence of the steam-bubble diameter was studied, and the results were validated with a previously published experimental report, which showed an agreement of approximately 2.5% for the adopted mesh size. The proposed solution may be appropriate for rapid design procedures for these types of devices.