Improvements of air flow distribution in a freezing tunnel using Airpak

AbstractIn a freezing tunnel, food products are cooled and frozen by cold circulating air. The products give off heat to the air, which is cooled down again in an air cooler. Refrigeration systems with freezing tunnels consume considerable amounts of energy and improvements in the tunnel design may reduce energy use. The necessary freezing time for products inside the tunnel depends strongly on air velocity and distribution. Uneven air velocity distribution results in non-homogeneous product freezing times and inefficient energy use for fans and refrigeration systems. The analysis of the tunnel design has been performed by computational fluid dynamics (CFD) simulations with the software tool ANSYS Airpak. The analysis is based on an existing freezing plant where different ceiling geometries have been tested for the same model. This was done in order to identify problem areas, to improve the design, and to obtain better air distribution and optimized fan power consumption. Results from the simulations show that fan power and air distribution can be strongly influenced by ceiling design and use of air guidance vanes, which may have a significant impact on the overall energy use for such a freezing tunnel. Several alternative ceiling designs resulted in a final version with reduction in total energy consumption of approximately 12% compared to the baseline configuration. The minimum air fluxes over the products were increased from 2.6 to 4kg/sm2; resulting in reduced necessary freezing time