Heat and mass transfer in a hydrofluidization system with multiple spheres

BELIS, E. E.; ZORRILLA, S. E.; PERALTA, J. M.

New Orleans

Congreso; Ift 2014 - Annual Meeting and Food Expo; 2014

Institute of Food Technologists

Hydrofluidization is a method of chilling and freezing of foods which consists of a circulating system that pumps a refrigerating liquid upwards through orifices or nozzles creating agitating jets. This method presents advantages related to the small equipment used and the improvement of the freezing of individual pieces of food. The objective of this work was to study the effect of the operative variables on the heat and mass transfer in a hydrofluidization system using several static spheres and round jets through multiphase mathematical modeling and CFD simulations. The system consisted in a cylindrical vessel with round orifices of 3 mm diameter at the bottom to generate the jets. A regularly spaced squared array of 20 mm diameter static potato (Solanum tuberosum L.) spheres was used as food model. An aqueous solution of NaCl 0.231 (w/w) was considered to model the liquid phase. The operative variables were the distance between the geometrical center of the orifices (S: 1 cm; 2 cm) and the spheres (L: 2 cm; 6 cm), refrigerant temperature (T: -5°C; -10°C), average velocity of the refrigerant fluid at the orifices (V: 1.18 m/s; 2.36 m/s) and the distance between the plane of the orifice plate and the stagnation point of the spheres (H: 1 cm; 5 cm). The representative variables of the transfer were: surface heat transfer coefficient, pressure coefficient, turbulence intensity, freezing time and central temperature of the sphere. In general, the heat and mass transfer in the liquid were most influenced by H, S, V and L. On the other hand, the heat transfer within the spheres was affected by S, V, H and L, and the mass transfer was influenced by T. This study will provide useful information in the efficient design of a hydrofluidization system which represents an attractive industrial method.