Radiation emitted from fluidizing particles adjacent to a heated surface in a fluidized bed

We experimentally investigated the radiation heat exchange occurring in a g as-solid fluidized bed (kept at 25 degreesC) between the fluidizing particl es and a remotely-heated heat transfer surface (30 degreesC). To evaluate t his heat exchange,radiation emitted from the fluidizing particles towards t he heated surface was measured through a transparent heat transfer surface using an infrared imager. Our experimental results revealed that the fluidi zing particles are mainly heated by conduction during the contact period wi th the surface and/or by gas convection in the thermal boundary layer, and that these heated particles frequently emit a significant amount of radiati on energy toward the surface. Based on these results, a method for evaluati ng the radiation heat exchange between the heat transfer surface and the fl uidizing particles is proposed. The proposed method shows that particle dia meter is one of the most significant parameters in the radiation heat excha nge, and predicts that the radiation heat exchange increases with increasin g particle diameter. (C) 2001 Editions scientifiques et medicales Elsevier SAS.