Photo‐sensor Methodology for Determining Residence Time Distributions of Particles in Continuous Flow Thermal Processing Systems

Abstract

ABSTRACT A method applying photo‐sensors was developed to determine particle residence time distributions in the holding tube of aseptic processing systems. Multiple sensor pairs installed around a transparent glass tube (50.8 mm, i.d.) created a two‐dimensional “optical‐grid” for detecting particle movement. Detection of spherical particles (polystyrene, 19.1 mm diameter) could be achieved at particle velocities below 2.67 m/s to comply with sensor response time. A normal distribution of particle residence times was obtained from 75 replicated runs. The laminar flow assumption for the fastest fluid element was found to be conservative for public safety concerns in solid‐liquid two‐phase systems using the single particle basis for sizing holding sections.