Experimental investigation of the fluid flow inside a hydrofluidisation freezing chamber
Abstract Hydrofluidisation freezing is a novel and promising food processing technology. This freezing method offers a high product quality, mostly due to the short process times resulting from high heat transfer coefficients. Consequently, hydrofluidisation freezing time is relatively short. Nevertheless, comprehensive experimental studies of this method are not available in the current literature. Therefore, the scope of this study was to experimentally investigate the fluid flow inside a hydrofluidisation chamber. The construction of the test rig used for the presented analysis enabled particle image velocimetry (PIV) measurements of the process. The PIV method was used for velocity field measurements. These measurements were conducted for various mass flow rates of the coolant and for various ratios of the distance between the sample and the orifice (H) to the orifice diameter (d). The results showed that the H/d ratio has a strong influence on the velocity of the fluid near the sample walls. The velocity of the fluid rapidly decreased for H/d higher than 14.0. Moreover, the increase of the mass flow rate and, in consequence, the coolant Reynolds number for H/d exceeding 14.0 did not affect significantly the velocity field around the analysed sample. Hence, the gathered results showed the importance of the correct design of the HF chamber in order to maximise the fluid flow velocity around the processed objects. Moreover, various velocity profiles were analysed showing the velocity variation under the sample. The collected velocity profiles and velocity fields were considered suitable for the hydrofluidisation freezing CFD models validation.