RESIDENCE TIME DISTRIBUTION OF LIQUIDS IN A CONTINUOUS TUBULAR THERMAL-PROCESSING SYSTEM - PART II - RELATING HOLD TUBE EFFICIENCY TO PROCESSING CONDITIONS

The concept of efficiency of a holding tube is essential to guarantee the safety of continuously processed fluid foods. A good prediction of efficiency allows a better control of the processing conditions guara nteeing product safer while decreasing product quality losses due to o verprocessing. Different published methods were compared to data obtai ned in this work and to reported data, to assess their ability to pred ict tube efficiency) in a range of Reynolds number (Re) covering lamin ar transient and turbulent flow Furthermore, a model assuming disperse d plug flow! and a power law relation between Peclet number (Pe) and R e was developed and evaluated. Published models were shown to be, in g eneral conservative for both laminar and turbulent flow but often over predicted the experimental efficiency in the zone of 2100<Re<4000. Dev iations between predicted and experimental values were very considerab le (errors from -25% to 90%). The model proposed has proved to be cons ervative over the whole range bur more accurate (errors up to 15%). (C ) 1998 Elsevier Science Limited. All rights reserved.