Numerical analysis of hydrofluidisation food freezing with moving products in different aqueous solutions by using CFD and MPM approaches

Abstract

Hydrofluidisation (HF) is an original method of food freezing that allows very high heat transfer coefficients to be reached and significantly reduces the freezing time of small foods. This paper presents a numerical study of HF for food products immersed in different liquids: binary solutions of ethanol (30%) and glycerol (40%) and a ternary solution of ethanol and glucose (15% and 25%). The particle movement (0.02 m diameter) was simulated using the Macroscopic Particle Model (MPM) approach to extend the CFD simulation by the particle flow, which affects the liquid phase velocity field. The numerical model developed in that study fully describes the hydrodynamics of HF process and is the most realistic out of all the numerical studies performed so far due to the ability to resolve the fluid flow locally on a smaller scale than in other models where the movement of foods in HF was introduced. Experiments with high-speed camera recordings validated the numerical model. A wide range of liquid mass flow rates in the range from 0.1 kg⋅s−1 to 2.0 kg⋅s−1 was investigated. As a result, heat transfer coefficients from 1 000 W⋅m−2⋅K−1 to 4 500 W⋅m−2⋅K−1 were reached, depending on the fluid mass flow rate. The liquid type had a minor effect on the heat transfer coefficient (HTC) but affected the behaviour of food samples. The effect of the food product suspension within the HF tank was noticed only for the ethanol solution with a moderate mass flow rate.