Temperature Visualization of Fluidizing Particles and Construction of a Heat Transfer Model in a Fluidizing Bed Heat Exchanger.

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This study deals with the heat transfer mechanisms at a microscopic level. Heat conduction during contact between a heat transfer surface and fluidizing particles, which is one of the effective heat transfer mechanisms in a gas-solid fluidized bed, has been empirically investigated. The temperatures of the fluidizing particles during the contact period is visualized with the aid of an infrared imager. This visualization reveals that the particles have been considerably heated in the thermal boundary layer on the heat transfer surface before contact. Based on the visualized temperature of the particles, the contact conductance between a fluidizing particle and the heat transfer surface is estimated by inverse analysis, and using the evaluated contact conductance, the contributions of the conductive heat transfer to the total heat transfer are also evaluated.In order to evaluate the contributions of the conductive heat transfer to a tube type heat transfer surface that is popular in practical fluidized beds, the validity of a heat transfer experiment that uses two types of spherical particles is evaluated. These particles used in the experiment are made of glass and aluminum and have the same diameter. Since the particles have almost the same density but deferent thermal conductivity, the deference of the total heat transfer is considered to correspond to the contributions of the conductive heat transfer. The contributions estimated for the same heat transfer surface as the visualization are in good agreement with those estimated by the visualization. Using the two types of particles, the contributions of the conductive heat transfer on a tube-type heat transfer surface are evaluated in a various fluidizing conditions.