The profiles of local heat transfer coefficient along the axial direction of a probe were measured in a 8m tall

186mm ID cold model fast flu-idized bed at different radial positions. All data were obtained by using a specially designed heat probe assembly. In the experiments elimination of axial thermal conduction and constant bulk density along the probe were ensured. The experiments show that regardless of the radial position where the probe is located

the local heat transfer coefficients decrease gradually from top to bottom of the probe. It means that the particles always aggregate at the probe surface

forming a layer and moving downwards along the probe surface if the probe is large enough. In light of this mechanism

the experiments have confirmed that the local heat transfer coefficients are mainly dependent on the local bulk density around the probe and the particle renewal frequency at the surface

which in turn vary with gas velocity. The contribution of gas convection can be neglected in comparison with that of the transient heat transfer between particles and the probe surface.