Mixing in Scraped Surface Heat Exchanger Geometry Using Mri

Mixing, as a unit operation, is a key component in the operation of scraped surface heat exchangers (SSHE) because of its importance in ensuring uniform heat treatment. In this study, two approaches were used to evaluate mixing effectiveness in a process geometry that simulates a closed type SSHE: the strain distribution function which was based on velocity profiles and statistical mixing indices based on concentration profiles. For the 1% carboxymethyl cellulose test solution under laminar flow conditions, the lower angular rotation speed and lower axial flow rate promoted mixing with respect to mixing intensity. The residence time, as characterized by the axial Reynolds Number, was the key factor for this statistic. The strain distribution function and mixing length scale were affected by the relative contribution of angular rotation to axial flow, which was expressed as the ratio of the angular Reynolds number to the axial Reynolds number. This work demonstrates the equivalence of evaluating mixedness by experimental concentration profiles and theoretical velocity profiles.