A Quantitative Study on the Effect of Rotation Rate on Radiation Heat Transfer in a Rotary Drum

Rotary drums are used to manufacture pharmaceuticals, cement, food, and other particulate products because of their high heat and mass transfer rates. These processes are governed by particle parameters, such as particle size, particle distribution, and shape, and operating parameters, such as rotation rate and fill level. Enormous energy savings are possible with further research in rotary drums due to potential increases in operating efficiency. This study investigates the drum rotation rate on particle bed temperature at temperatures above 500 °C to see the role that radiation heat transfer plays in this process. 2 mm silica beads and a stainless steel rotary drum were used at a fill level of 25% with rotation rates from 2-10 rpm. A new setup and procedure were developed using heating coils and an IR camera to reach high temperatures. The inner drum wall temperature exceeded the outer drum wall temperature because the steel transmitted more heat into the drum at higher temperatures. Although it was unclear whether the heat transfer rate was affected by the increasing rotation rate, the highest final average particle temperature was obtained at 5 rpm. The particle bed temperature distribution narrowed as the rotation rate increased because, at higher rotation rates, more particles are in contact with the drum wall than at lower rotation rates.