Yl. Ding et al., Some aspects of heat transfer in rolling mode rotating drums operated at low to medium temperatures, POWD TECH, 121(2-3), 2001, pp. 168-181
Rotating drums in industries are often operated at elevated temperatures. H
eat transfer in such devices therefore plays a prime role. However, the con
trolling steps in heat transfer have not been fully clarified though a cons
iderable amount of work has been carried out. In this paper, heat transfer
in rotating drums operated in a rolling mode is assessed. The focus is on d
irect heating operations at low to medium temperatures, where thermal radia
tion is unimportant. It is shown that heat transfer from the covered wall t
o the particle bed is the dominant mechanism in supplying heat to the bed.
Heat transfer between the freeboard gas and the exposed surface of the free
cascading layer accounts for only a small portion, in contradiction to our
previously held opinion. The heat transfer rate between the freeboard gas
and the uncovered drum wall may be comparable to that between the covered d
rum wall and the particle bed indicating that both steps could be controlli
ng. If heat is supplied to the boundaries of the particle bed rapidly, and
macroscopic particle mixing is rapid, then heat transfer within the bed may
be controlled by either or both of gas-solid heat transfer and heat conduc
tion within individual particles depending upon the physical properties of
both interstitial gas and particles. Although theoretical analyses are prin
cipally used in this work, comparison with experiments is also made where a
ppropriate. (C) 2001 Elsevier Science BN. All rights reserved.