Basic Studies on Fluidized Bed Heat Exchanger (Heat Transfer from Single Row of Horizontal Rectangular Tubes Immersed in Floating Low Density Particles) : Heat Transfer, Power, Combustion, Thermophysical Properties

Using the low density particles (polystyrene hollow spheres) described in the 1st report, mean heat transfer coefficients from a single row of horizontal cylindrical tubes immersed in floating particles were measured, with the aim of reducing pressure drop in a fluidized bed heat exchanger. In this study, furthermore, in order to make particles float stably around tubes, rectangular tubes (aspect ratio: 30/3) were used because the change in flow area between the tubes is small; that is, the change in flow velocity between the tubes is small compared with that of cylindrical tubes. The results show that: 1 L0/Lh≥1, and the mean heat transfer coefficients are independent of both L0 and Lh, in the same way as with cylindrical tubes. 2 Mean heat transfer coefficients decrease slightly more than those with cylindrical tubes. 3 However, since rectangular tubes can be arranged more densely than cylindrical tubes, their thermal performance under the same pumping power is improved to about three times that of cylindrical tubes.