This paper deals with the experimental examination of microscale mechanisms of heat transfer augmentation of fluidized beds; the direct-contact heat exchange from a heat transfer surface to fluidized particles was estimated for particles of various sizes. Contact period and frequency between the particles and heat transfer surface were measured by employing an optical technique, and the heat transfer between them was analytically evaluated. The obtained results showed that unsteady heat conduction to the fluidized particles plays an important role to the heat transfer augmentation, especially under the condition of incipient fluidization while the contribution of direct-contact heat exchange evidently decreases with increasing the particle diameter and fluid velocity.