Substantiation of air flow speed rate for minimizing energy costs during fluidized-bed freezing of honeysuckle berries

Abstract

Fluidized-bed freezing allows at best preserving the quality characteristics of fruits and berries. Designing of low-temperature processing in fluidized-bed fast-freezing systems is a complex task that requires taking into account various factors that have multidirectional influence on the process. The development of affordable energy-efficient systems that ensure high quality of frozen fruit and berry raw materials is an important direction in the development of agro-industrial technologies. The research goal was to analyze low-temperature processing regimes during fluidized-bed freezing of honeysuckle berries from the point of view of optimizing energy costs when implementing the process. The analysis of energy costs for the implementation of fluidized-bed freezing was based on the theory of similarity in heat transfer processes using criterion equations of the theory of similarity. Calculations were made using Excels spreadsheets and the MathCad software package. The range of fluidization rates for freezing honeysuckle berries was determined in the air temperature range from -15°C to -45°C. The acceptable range of air flow speeds is from 1.5 to 9 m s. This range provides a fluidization regime while preventing the removal of honeysuckle berries from the working area of the system. The minimum energy costs for implementing fluidized-bed freezing process for honeysuckle berries will occur at an air speed of about 1.5-2 m s at a minimum air temperature.  The research findings allow concluding that it is advisable to lower the air temperature in fluidized-bed fast-freezing system at an air speed close to the lower limit of the fluidization speed range. In this case, the energy consumption for organizing air movement when freezing 1 kg of berries will be 45 kJ at an air speed of 2 m s and an air temperature of -40°C.