Residence Time Distribution of Liquids in a Continuous Tubular Thermal Processing System Part I: Relating RTD to Processing Conditions

A systematic experimental study on residence time distribution (RTD) in tubular flow was performed, covering a wide range of processing conditions. The flow of water in various sections of a tubular continuous thermal processing system was analysed using the classical Danckwerts approach. Methylene blue was used as tracer and different constant temperatures (25-80°C) and flow rates (80-380 l/ h) were tested. These conditions yielded mean residence times up to 6 min and Reynolds numbers between 1350 and 9700. Various models were fitted to the experimental data, and the dispersion model showed to yield the best fit. Peak analysis led to both accurate and precise as well as conservative parameters, when compared to other methods of parameter estimation. Results revealed that fluid dispersion in tubular flow (Peclet number) can be related to processing conditions (Reynolds number) by a power law model. Results were compared to published correlations.