Simulação computacional de transferência de momentum e calor em um túnel de congelamento

Abstract

The main characteristic of the rapid freezing tunnel is the presence of axial or centrifugal blowers, which circulate the air over the products in a controlled manner, causing extremely rapid cooling due to forced convection. In the food industry, this equipment is used to freeze various products such as vegetables, bakery products, fish fillets and prepared foods. The computational fluid dynamics, known as CFD (Computational Fluid Dynamics) uses computational methods for simulating transport phenomena, thus obtaining distributions of speed and temperature fields. This work aimed to predict such fields in a freezing tunnel. Additionally, it was proposed, with the intention of improving the uniformity of the speed and temperature fields, the application of fins to direct the gas flow. The Ansys-Fluent® commercial package. was used to solve the computational model using the finite volume method. The three-dimensional simulations developed involved the transport equations: conservation of mass, amount of movement and energy transfer. The algebraic equations were solved by the AMG algorithm (Algebraic Multi-Grid), using as a convergence criterion that the sum of the normalized residues was less than 1x10-5 for all variables. The uniform distribution of gas velocity at the entrance was considered. The results obtained showed that the conventional geometry of the freezing tunnel causes the air flow to be concentrated in a region of the tunnel and that, when adding baffles, the air flow was directed to the region where the products are stored. This redirection caused a drop of 15% in the temperature values of the full tunnel, in addition, it presented a similar behavior to the empty tunnel. In addition, computer simulations proved to be sufficient to predict the phenomenon of heat transfer and momentum.