STUDY ON THE HEAT-EXCHANGER USING FLUIDIZED-BED .1. CHARACTERISTICS OF WALL TO BED HEAT-TRANSFER IN VERTICAL TUBE

The application of the fluidized bed to a heat exchanger is intended as a means of augmentation of heat transfer. The particles of glass beads are fluidized by air flow in the vertical tube of inside diameter D=60mm. The surface with a stainless foil placed on the inside of tube is heated electrically so that the heat flux is constant. The distribution of the local Nusselt numbers in the vertical direction was measured for particle diameter dp=0.3∼3.0mm, initial bed height L0/D=0∼3.33 and air velocity U^-/Umf=0.2∼10.0. Moreover, the mean Nusselt number and the volume goodness factor were examined for performance comparison under the condition of constant pumping power. An excellent performance of fluidized bed heat exchanger was shown, and the effective height of heat transfer surface was determined.