HEAT-TRANSFER TO A HORIZONTAL TUBE IN THE SPLASH ZONE OF A BUBBLING FLUIDIZED-BED, AN EXPERIMENTAL-STUDY OF PARTICLE-SIZE EFFECTS

The experimental results of an investigation involving particle size effects on the heat transfer for a horizontal tube located in the splash zone of a high-temperature bubbling fluidized bed are reported. This article is the second of a series [1] that investigates specific operating parameters of bubbling fluidized beds. The array of experimental conditions for this work involved three particle sizes, of nominal 1.1, 2, and 2.9 mm in diameter; four bed temperatures, 700, 810, 908, and 1003 K; and three tube locations, -127, 64 and 406 mm relative to the tube centerline to nonfluidized bed surface. The tube locations are representative of a tube totally immersed in the bed, located in the splash zone, and located in the freeboard, respectively. Convective and blackbody radiative heat transfer coefficient variations are presented as functions of the nondimensionalized velocity ratio and of the particle size for the 1003-K case. Maximum convective and blackbody radiative heat transfer coefficients are tabulated for the other temperatures and particle sizes. The tube outside diameter was 51 mm, and the supeficial velocity was varied from near-minimum fluidization conditions (U-mf) to over 2 U-mf.