Avaliação do fluxo de ar e da perda de carga localizada em junções de dutos de ventilação industrial através da fluidodinâmica computacional (CFD)

Abstract

The increase in air pollution has received increasing attention in recent decades. The industries are important contributors to the emission of pollutants into the air, requiring the use of environmental controls, such as local exhaust ventilation systems. Thus, for the correct use of these systems, it is necessary that they are effective and have a satisfactory efficiency, requiring a correct dimensioning. For this design, important factors such as pressure drop and flow dynamics must be precisely studied and measured. One of the main contributors to the dynamics and pressure drop in ventilation systems are the joints. Thus, this work aimed to evaluate the flow dynamics at junctions of local exhaust ventilation systems, examining the influence of the angle of the secondary flow and the ratio between the flows that flow into the component. For this study, a real small-scale industrial ventilation plant was used, whose geometry and flow conditions were modeled using ANSYS CFX 19.2 software. The numerical model was solved using a mesh of 3.8 million nodes and adopting the Shear Stress Transport (SST) turbulence model. The numerical model created was validated by carrying out experimental measurements in the ventilation plant, in which the numerical and measured results in the field were statistically compared using the Kruskal-Wallis Hypothesis Test, at a significance level of 5%, where it proved the validity of the numerical model. Twelve cases were simulated from the combination of the variation of the secondary branch inlet angle and the ratio between the secondary and main flows, maintaining a flow velocity around 20m/s. The results showed the existence and influence of turbulence phenomena in the region where the pipelines join, becoming more intense as the studied factors increase (inlet angle and flow rate). The results were also in line with the empirical methods described in the literature and it was found that there is a direct relationship between the factors studied, the pressure drop and static pressure after joining, suggesting the proposition of an alternative way of calculating this last parameter .