Numerical modelling of refrigerant flow field inside hydrofluidisation food freezing system

Food freezing method of hydrofluidisation is based on submerging small food products in appropriate water solution, which is pumped through orifices in order to intensify heat transfer between food products and the liquid by creating agitating jets. Highly turbulent liquid flow allows one to obtain significantly higher heat transfer coefficients comparing with common methods which results in rapid food freezing. To investigate the refrigerant flow field in such a system and convective heat transfer between the fluid and food products, the CFD model was proposed. In addition, the hydrofluidisation food freezing unit has been designed to study the process of turbulent refrigerant flow over a surface of food samples, which were replaced by spherical artificial objects having 20 mm in diameter and placed at fixed position within the coolant tank. The liquid used for the process of freezing is water-ethanol solute. The developed numerical model presented in this study employs k-ω SST or RSM BSL turbulence models to predict the refrigerant velocity because they prove excellent performance for wall-bounded flows in similar cases. Numerical model validation has been performed on the test rig using PIV technique, which allowed one to capture refrigerant flow field within the most significant areas, i.e. within the jet and around the sphere. The measurements confirmed that the CFD model predicts the fluid flow within the system with high accuracy.