MEASUREMENT OF HEAT-TRANSFER COEFFICIENTS IN ROTATING LIQUID/PARTICULATE SYSTEMS

A new method, involving the use of liquid crystals as temperature sensors, was developed to measure surface temperatures on moving particles. The method involves coating the monitored particles with aqueous solutions of encapsulated liquid crystals and recording the color changes on the particle surface as a function of temperature. Experimentally measured particle surface and liquid temperatures were used to calculate heat transfer coefficients for water-heated, axially rotating, cylindrical acrylic vessels containing liquid and solid spherical particles. The theoretical analysis associated with calculating the heat transfer coefficients from the experimental data is presented. The method is illustrated by measuring overall (heating medium/container wall/internal liquid) and liquid-particle film heat transfer coefficients for Teflon spheres in deionized water and aluminum spheres in 1.5 cSt silicone fluid.