Study on cooling performance of rapid cooling system based on vacuum spray flash evaporation

Abstract

• Vacuum spray flash cooling (VSFC) system was used for the first time with rapid cooling. • VSFC could cool almost six times fast than the freezer. • The cooling process of beverages could be divided into two stages. • The relevant operational parameters that could optimize VSFC cooling performance were studied. • The optimal discharge coefficient of nozzle was found in VSFC. The present study proposes a rapid cooling method based on vacuum spray flash evaporation, and establishes an experimental system to study the cooling performance of this method by taking beverages as an example. The feasibility and superiority of vacuum spray flash cooling (VSFC) are demonstrated by making the comparisons with the existing rapid cooling methods. A cooling performance evaluation is presented concentrating on the influence of the discharge coefficients of nozzle, multi-nozzle array, and vacuum degree of flash chamber. Meanwhile, the relevant operational parameters of VSFC are optimized. Experiments have shown that the VSFC cools almost six times faster than a freezer. Combined with the simulation, it is found that the cooling process of beverages could be divided into the initiating enhancement stage and the gradual decline stage, in accordance with the characteristics of the internal flow of the beverage during rapid cooling. Parametric analysis indicates that there is an optimal discharge coefficient of nozzles in order to achieve maximum cooling rate for VSFC.