Numerical modelling of the food freezing process in a quasi-hydrofluidisation system

Abstract

The paper presents a study of food freezing using hydrofluidisation method, characterised by very high heat transfer coefficients exceeding 2500 W · m−2 K−1, which constitutes a novel and promising technology. A numerical analysis of a system with a stationary group of food products was performed. This study aimed to investigate the geometrical parameters governing the freezing process, i.e., the position of food products above the orifices (from 50 mm to 70 mm), their mutual position, the diameter of orifices (3 mm or 5 mm), and the spacing of the orifices in an array (from 8 mm to 12 mm). In this method, the freezing time was from 3 min for 10 mm spherical food sample in moderate refrigerating medium temperatures up to 12 min for 30 mm spherical sample. Moreover, the freezing times at different liquid temperatures were compared in the range of −20 °C to −5 °C. Reducing the temperature by 5 K may lead to shortening the process by up to 50%. The hydrofluidisation method was assessed versus the immersion freezing for spherical products of different sizes showing the reduction of the process time from about 35% to over 60%.