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 unifo rm heat treatment. In this study, two approaches were used to evaluate mixi ng effectiveness in a process geometry that simulates a closed type SSHE: t he strain distribution function which was based on velocity profiles and st atistical mixing indices based on concentration profiles. For the 1% carbox ymethyl cellulose test solution under laminar flow conditions, the lower an gular rotation speed and lower axial flow rate promoted mixing with respect to mixing intensity. The residence time, as characterized by the axial Rey nolds Number, was the key factor for this statistic. The strain distributio n function and mixing length scale were affected by the relative contributi on of angular rotation to axial flow, which was expressed as the ratio of t he angular Reynolds number to the axial Reynolds number. This work demonstr ates the equivalence of evaluating mixedness by experimental concentration profiles and theoretical velocity profiles.