Two-Phase Flow and Heat Transfer in Fluidized Beds. Final Report, August 1, 1975-June 30, 1978

摘要

Cold modeling studies of fluidized-bed behavior related to coal combustion were conducted to provide information required for the design and optimization of fluidized-bed systems for power generation. Data for flow regime, bed expansion (void fraction), transverse thermal conductivity, and bare- and finned-tube heat transfer were obtained for beds of single and mixed particle sizes fluidized with air and refrigerant R-12 at room temperature. The ranges of primary variables covered in the experimental work reported here include bed cross sections of 0.3 meter by 0.3 meter and 0.6 meter by 0.6 meter, static bed heights from 25 cm to 70 cm, glass particle sizes of 650 mu m and 2600 mu m, and silica sand sizes in the same range, air at pressures from one to ten atmospheres and refrigerant R-12 at vapor densities equal to those of air at five and ten atmospheres, air velocities up to 6.5 m/s and 3.2 m/s at one and ten atmospheres pressure, respectively. The staggered horizontal tube banks investigated in the flow and heat transfer experiments included 3.2-cm o.d. bare tubes and 2.5-cm i.d. helically finned tubes having a 5.1-cm fin o.d. The stainless steel fins were 0.27 cm and 0.15 cm thick at fin spacings of 0.98 fin/cm to 1.97 fins/cm, respectively. Five- and ten-row tube banks were tested. Generalized predictive models for the bed flow regimes, the bed expansion, the solids circulation rates, and the heat transfer to tube banks were developed and shown to be qualified by the data for both local and average bed quantities. The information and observations described here lend sufficient support to the use of higher energy density fluidized-bed combustors at increased superficial gas velocities to justify further work at high temperature aimed at validating this performance improvement. (ERA citation 05:034033)