Bm. Wagenaar et al., FLUOROPTIC MEASUREMENTS OF THE LOCAL HEAT-TRANSFER COEFFICIENT INSIDETHE ROTATING CONE REACTOR, Chemical Engineering Science, 49(22), 1994, pp. 3791-3801
The rotating cone reactor is a novel reactor type for rapid thermal pr
ocessing of solids. This paper focuses on the experimental determinati
on of the gas-to-particle heat transfer coefficient. This quantity has
been measured for several particle diameters (average size of 150, 28
0 and 425 mu m) and cone rotational frequencies (11.3 and 28.3 Hz). Th
e gas-to-particle heat transfer coefficient obtained from these experi
ments varied between 280 and 1030 W m(-2) K-1. Experimental parameters
which were kept constant in this study were the particle mass flow ra
te (5 g s(-1)), the cone geometry (cone top angle pi/3 radians) and th
e temperature of the particle feed (280 degrees C). The experimentally
determined heat transfer coefficients were represented in dimensionle
ss form as a function of the particle Reynolds number. The particle Re
ynolds number has been obtained from measurements of the local gas-pha
se velocity and the local particle velocity. Analysis of the experimen
tal results revealed that the gas-to-particle heat transfer coefficien
ts could roughly be represented by the well-established Ranz-Marshall
correlation (Rant and Marshall, 1952, Chem. Engng Progress 48, 173) fo
r isolated non-rotating particles. The difference between the experime
ntally observed particle Nusselt numbers and the theoretically predict
ed Nusselt numbers based on the Ranz-Marshall equation is probably due
to the influence of particle rotation on the gas-to-particle heat tra
nsfer process. Calculations showed that the time in which the particle
s lose half of their rotation frequency is typically in the order of t
he particle residence time in the rotating cone reactor.