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Manual welding operations are performed inside the engine room of a liquefied natural gas carrier under construction. The welders are at risk of exposure to welding fumes in case of poor ventilation. Therefore, ventilation fans are installed at shipbuilding sites to improve indoor air quality. Although ensuring the respiratory health of welders is important, studies focusing on ventilation in the ship engine room have not been conducted. Therefore, the ventilation efficiency was evaluated herein based on the placement of ventilation fans to alleviate air stagnation using a computational fluid dynamic (CFD) model operating on Fluent. The mean age of air (MAA) was computed to assess the ventilation efficiency. In addition, particles with size and physical properties similar to welding fumes were sourced assuming 30 welders in the engine room. Results revealed that ventilation fan and/or exhaust in enclosed spaces contributes significantly to alleviating the MAA level. MAA and particle distribution did not correlate well due to the different properties of air and the iron oxide particle. Therefore, to determine the optimal ventilation fan displacement, particle motion should be studied along with performing MAA analysis. The proposed CFD model potentially guides to improvement of the working environments and respiratory health of welders.

Manual welding operations are performed inside the engine room of a liquefied natural gas carrier under construction. The welders are at risk of exposure to welding fumes in case of poor ventilation. Therefore, ventilation fans are installed at shipbuilding sites to improve indoor air quality. Although ensuring the respiratory health of welders is important, studies focusing on ventilation in the ship engine room have not been conducted. Therefore, the ventilation efficiency was evaluated herein based on the placement of ventilation fans to alleviate air stagnation using a computational fluid dynamic (CFD) model operating on Fluent. The mean age of air (MAA) was computed to assess the ventilation efficiency. In addition, particles with size and physical properties similar to welding fumes were sourced assuming 30 welders in the engine room. Results revealed that ventilation fan and/or exhaust in enclosed spaces contributes significantly to alleviating the MAA level. MAA and particle distribution did not correlate well due to the different properties of air and the iron oxide particle. Therefore, to determine the optimal ventilation fan displacement, particle motion should be studied along with performing MAA analysis. The proposed CFD model potentially guides to improvement of the working environments and respiratory health of welders. [ABSTRACT FROM AUTHOR]

Single-heading tunnels in underground metal mines have high air pollutant concentrations, chaotic airflow, and low pollutant diffusion efficiency in high-altitude areas, resulting in poor air exchange. Based on Pulang copper mine (China), a computational fluid dynamics case using the steady Reynolds-averaged Navier–Stokes equations with a k-omega turbulence model was developed to study certain factors influencing the air exchange of single-heading tunnels, and was combined with an orthogonal experimental method to simulate the mean age of air (MAA) under different working conditions. This study revealed the ranking of the importance of some factors on the air exchange via sensitivity analysis. The MAA generally increases with the increasing distance between the duct and the heading face and the increasing diameter of the oxygen supply duct. This study's optimal distance and diameter can reduce MAA by 14.7% and 9.9%, respectively. Placing the oxygen supply duct and the duct on the same side and using an 800/1000 mm inner diameter duct can effectively reduce the MAA by 6.7% and 4.2%, respectively, in this study. The findings of this study can optimize air exchange in the Pulang copper mine, and can also be referenced for the optimization of air exchange in high-altitude highway or railway tunnels being excavated. [ABSTRACT FROM AUTHOR]

Single-heading tunnels in underground metal mines have high air pollutant concentrations, chaotic airflow, and low pollutant diffusion efficiency in high-altitude areas, resulting in poor air exchange. Based on Pulang copper mine (China), a computational fluid dynamics case using the steady Reynolds-averaged Navier–Stokes equations with a k-omega turbulence model was developed to study certain factors influencing the air exchange of single-heading tunnels, and was combined with an orthogonal experimental method to simulate the mean age of air (MAA) under different working conditions. This study revealed the ranking of the importance of some factors on the air exchange via sensitivity analysis. The MAA generally increases with the increasing distance between the duct and the heading face and the increasing diameter of the oxygen supply duct. This study’s optimal distance and diameter can reduce MAA by 14.7% and 9.9%, respectively. Placing the oxygen supply duct and the duct on the same side and using an 800/1000 mm inner diameter duct can effectively reduce the MAA by 6.7% and 4.2%, respectively, in this study. The findings of this study can optimize air exchange in the Pulang copper mine, and can also be referenced for the optimization of air exchange in high-altitude highway or railway tunnels being excavated.

• IAQ is assessed for an Iranian dry climate house equipped with wind tower. • CFD setup is validated against experimental data conducted on a 1:25 scale model. • Low values of MAA show that quick replacement of air is the target. • As a source of fresh air, the courtyard significantly enhances IAQ in the parlor. • IAQ is highly dependent on the flow pattern rather than the wind tower performance. CFD simulations at various wind directions were performed to assess air distribution quality within a traditional Iranian dry climate house integrated with a four-sided wind tower. The house's summer room, parlor, connects the wind tower to a courtyard by its cross-openings, representing the layout of most vernacular houses in Yazd city, Iran. This study pursues the strategies applied in a traditional passive ventilation system by focusing on its interaction with adjoining architectural features and the surrounding environment. The urban terrain was simulated using Atmospheric Boundary Layer profiles and modeling the ground surface roughness. Indoor Air Quality (IAQ) parameters such as Mean Age of Air, Air Change Effectiveness, and Air Change Rate were analyzed. The CFD setup was validated through scaled wind tunnel experiments and replicating the same conditions in CFD modeling, which showed a good agreement. Results indicate that IAQ is acceptable at around 77% of the outdoor wind angles due to the courtyard's significant influence as the secondary source of fresh air, leading to quick heat removal from the environment as an effective strategy that suits the hot-arid climate. Investigating the system's failures shows that IAQ is highly dependent on the flow pattern rather than the wind tower functionality. [ABSTRACT FROM AUTHOR]