Industrial processes rarely involve a single fluid; rather, it is common for different phases, components or gaseous species to interact with one another. From industrial furnaces and extraction systems to reactors and ventilation equipment, the accurate characterisation of the mixture’s behaviour is essential to ensuring the safety, efficiency and quality of the process. Consequently, CFD simulations of gas mixtures represent an area of great industrial interest.
How is CFD simulation applied to gas mixtures?
When two or more gases come into contact within a pipe, chamber or reactor, it is not sufficient to simply solve for the fluid’s velocity and pressure fields. Unlike a conventional CFD simulation, it is necessary to simultaneously calculate the motion of the mixture and the concentration of each chemical species present in the domain.
To this end, species transport models are used, which take into account phenomena such as convection and turbulent diffusion, as well as the influence of geometry, gas properties and operating conditions. Unlike a simulation of a single gas, where the fluid properties are uniform and constant throughout the domain, an additional transport equation must be solved for each species present, and the local properties of the mixture—density, viscosity and thermal conductivity—must be continuously updated, as these vary from point to point depending on the local composition.
Applications of CFD simulation for gas mixing
The applications of this technology are wide-ranging and span numerous industrial sectors. Some of the areas where these simulations add the most value include:
- Industrial extraction and ventilation systems: CFD simulation enables the characterisation of gas distribution within extractors, hoods and ducts, assessing the efficiency of capture and the influence of operating conditions on the flow.
- Furnaces and thermal processes: In equipment where gases of different temperatures and compositions coexist, the species model allows for the simultaneous study of mixing and heat transfer, identifying areas of gas accumulation or undesirable thermal gradients.
- Analysis of gas leaks and dispersion: In industrial facilities where there is a risk of leaks of toxic, flammable or polluting gases, CFD simulation enables the dispersion of the gas cloud to be predicted based on environmental conditions, available ventilation and the characteristics of the leak. This type of analysis is key to assessing risk areas, sizing emergency detection and ventilation systems, and ensuring compliance with industrial safety regulations.
- Emissions control systems: CFD simulation enables the efficiency of pollutant dilution systems or the correct distribution of purge flows to be assessed, thereby helping to ensure compliance with environmental and safety requirements.
Case study
Como ejemplo de aplicación industrial, recientemente en ICEMM realizamos un estudio del sistema de extracción acoplado a un horno de fundición de cobre usando Cradle CFD. El objetivo fue validar el funcionamiento del extractor y evaluar su influencia sobre el sistema, caracterizando el comportamiento del flujo mediante la validación del campo de velocidades, la distribución de temperatura y la difusión de los componentes gaseosos.
The study was carried out by taking into account the gas mixing model within the equipment, as well as heat sources and the particle module with masses coupled to the fluid. Two corresponding geometric configurations were analysed by solving the compressible flow equations with turbulence in transient conditions.
The following image shows the streamlines for one of the configurations studied, allowing the distribution of flow within the system to be visualised.
