The following unsteady local properties were measured simultaneously around a horizontal heated circular cylinder in a gas-solid fluidized bed for three kinds of particles with different diameters; (1) the heat transfer coefficient, (2) wall pressure and (3) the discrimination between emulsion and void phases. The unsteady signals were analyzed statistically. The arrival frequency of bubbles on the cylinder surface, the mean contact time of the emulsion and bubbles with the cylinder surface, the rate of contribution of the emulsion and bubbles to the heat transfer coefficient, the contact heat transfer coefficient of emulsion with the cylinder surface, etc., were obtained. On the basis of these characteristics, the effects of the diameters of the particles were estabished quantitatively. Moreover, a new model of heat transfer around a circular cylinder, considering the effect of the sliding emulsion, was applied to the experimental results, and the validity of the model and the dominant mechanism of heat transfer were clarified.