An investigation of heat transfer of flexible fibers in a rotating drum dryer using the Discrete Element Method

Abstract

A flexible fiber Discrete Element Method (DEM) is advanced to investigate heat transfer of fibrous materials in a rotating drum dryer. Heat exchange is considered between fiber and fiber, fiber and drum, fiber and air, and air and drum. In addition, the heat conduction and temperature variation within a single fiber along its major axis are also modeled. It is observed that the heat conduction through solid-solid contacts is much faster than the air-solid convection. Fibers of larger flexibility or smaller aspect ratios are packed more densely with larger numbers of fiber-fiber and fiber-wall contacts, causing a larger heat transfer coefficient between the fiber bed and drum. A larger fiber-fiber friction coefficient leads to a smaller heat transfer coefficient by inhibiting the movement of contacting fibers and reducing the number of contacts. Three distinct regimes are identified for the complex effect of fiber-wall friction coefficient on the heat transfer.