Calculation on heat transfer from the particles to the heat exchange surface during the cooling stage of refined standard sugar drying using the pulsed fluidised bed

Abstract

During material drying, after the material has been dried to the desired moisture content, the next step in the drying process is to cool the dried materials to the storage temperature. In practice, there are many solutions for cooling the material, but the method of using a heat exchange tube containing a cooling medium is considered an effective solution. The article presents the calculation of heat transfer from the refined standard (RS) sugar granule layers in the minimum pulsed fluidised state to the heat exchange surface. The study has clarified the relationship between the convection heat transfer coefficient of the hot-dried granules and the heat exchange surface, as well as its correlation with the particle size. Specifically, for RS sugar granules with a size equal to or less than 0.8 mm, the convection heat transfer coefficient is determined to be 251.17 W/(m².K). Conversely, for particles with a size of about 1.0 mm, the heat transfer coefficient is determined to be 172.66 W/(m².K). The study results showed that the convective heat transfer coefficient depends on the particle size. Smaller particles have larger convective heat transfer coefficients. Specifically, with RS sugar particles, the particle diameter is 20% smaller but the convective heat transfer coefficient is 45% higher.