Investigation of the Energy-Saving Method during Candied Fruits Filtration Drying

Abstract

The drying process, which is the limiting and power-consuming stage of candied fruits production, has been considered. The heat-transfer processes during the filtration drying of pumpkin candied fruit have been investigated. The filtration drying of finished candied fruits (80 °C) is the filtration of a hot heat agent (100 °C) in the direction of "candied layers – grate". As a result of experimental studies, the kinetic curves of candied fruits drying, as well as the dependence of temperature on the height of the candied fruit layer, were obtained. The experimental data confirm the zonal mechanism of the filtration drying.
It was found that during the filtration drying, the upper layers, which reached their final moisture content, overheat and accumulate a considerable amount of unused energy. It was proved that the accumulated energy can be used for drying the lower layers with simultaneous cooling the upper ones. On the basis of the equation of non-stationary heat-mass transfer, the amount of heat is calculated, which will be sufficient to dry the bottom layer. The stoppage time of hot heat agent supply and start of cold heat agent supply were determined. Filtration of cold heat agent through a layer of candied fruits makes it possible to cool the layer, reduce drying time and energy costs for the process.
Dried candied fruits have sufficient shelf life, good taste and organoleptic properties.