Basic Studies On A New Fluidized Bed Heat Exchanger

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In order to improve the performance(especially pressure drop) of a fluidized bed heat exchanger, low density particles were employed. The tests were conducted with cylindrical tubes by varying the location of the tubes, static bed height, tube pitches and air velocities. Furthermore, in order to make particles stably floating around tubes, rectangular tubes were used because the change of the flow area between the tubes is small. Mean heat transfer coefficients were evaluated in relation to pressure drop. And effects of particles and effects of the ratio of tube diameter to particle size to heat transfer were carried out. Finally, mechanism of heat transfer was discussed by the results of the motion of particles at the surface of tubes using a capacitance probe.The results show that; 1. Mean heat transfer coefficients are independent of both the location of the tubes and static bed height in the case of the latter is larger than the former. 2. Mean heat transfer coefficient decreases with the tube pitch decreases, because the particules can not float stably around the tubes. 3. Mean heat transfer coefficients of rectangular tube decrease slightly more than those of cylindrical tubes. 4. But, as rectangular tubes are able to be arranged more densely than cylindrical tubes, the thermal performance under equal pumping power is improved about three times for that of cylindrical tubes. 5. The dense-phase and the lean-phase varied with air flow rate and particle size. 6. Local heat transfer coefficient increased by the effect of surface renewal due to the leanphase.