(536h) Conduction and Radiation Heat Transfer in a Rotary Drum

Rotary drums deliver high heat and mass transfer rates, making them extensively useful for powder mixing and heating processes in metallurgical, cement, mining, pharmaceutical, detergent and other particulate processing applications. However, these processes are challenging to model and operate because of the complex interactions affected by the particle parameters and process conditions such as particle size and distribution, shape, composition, fill level, rotation rate, and operating temperature.

Experiments are performed using 1-4 mm diameter silica beads at fill levels from 10–25% and rotation rates from 0–10 rpm. The granular flow and heat transfer by conduction and radiation are investigated inside a 6-inch diameter and 3-inch-long stainless-steel rotary drum. The drum is attached to two 10-inch titanium wheels, hence preventing the direct contact of the drum wall with the rollers. One end of the drum is closed using a transparent quartz window, capable of handling high temperatures. Another end of the drum is closed using a sapphire window, compatible with an IR camera, specifically chosen to obtain a high transmittance to the infrared light. The drum walls are maintained at a desired high temperature using Ni-Cr resistive wires and a PID controller. The particle bed temperature evolution is recorded on the IR camera, which is used to determine the average particle bed temperature over time.

The current experimental research is focused on understanding the effect of particle size, fill level, rotation rates, and their interactions on heating by conduction and radiation at high temperatures (>600ºC). This work will enable the determination of the optimal operating conditions for a rotary drum for improving energy efficiency of the process. It will also serve to bridge the gap in the literature for experimental data and validating simulation-based research.