Predição de escoamento de ar em um secador tipo túnel: Avaliação do uso de placas de direcionamento de fluxo e de modelos de turbulência

Abstract

The computational fluid dynamics, known as CFD (Computational Fluid Dynamics) uses computational methods to simulate transport phenomena, thus obtaining distributions of speed, pressure, concentration and temperature profiles. This work aimed to evaluate the use of flow direction plates and turbulence models usually reported in the literature k-ɛ, BSL, SSG and SST in the prediction of speed profiles during air flow in a convective dryer (Eco Educational Engineering, MD018, Brazil). Air flow and velocity fields were determined using the commercial package AnsysCFX®. The three-dimensional simulations developed involved the transport equations: conservation of mass, amount of movement and energy transfer. A finite volume numerical method was used to calculate partial differential equations. The algebraic equations were solved by the AMG algorithm (Algebraic Multi-Grid), using as a convergence criterion the sum of normalized residues less than 1x10-6 for all variables. The pressure-velocity coupling was approximated using the trilinear method. In the simulations, a permanent flow regime was considered. The boundary conditions were: uniform air speed at the entrance of the air supply duct, static pressure at 0 Pa at the exit of the dryer and condition of non-slip on the walls of the dryer. The use of air direction plates provided greater uniformity of the current lines. As there are no significant changes between the velocity profiles obtained with the turbulence models, it was understood that the k-ε model is the most appropriate because it presents a shorter simulation time and is capable of reproducing the phenomenological behavior of the air flowing in a tunnel dryer.