Karl V. Jacob

Bed-to-surface heat transfer for vertical U-tubes in a high-pressure slugging hydrogen-fluidized bed of carbon-supported catalyst powder

Abstract Bed-to-surface heat transfer coefficients h w are determined experimentally for vertical U-tubes in a high-pressure (3549 - 8720 kPa), pilot-scale, slugging, hydrogen-fluidized bed of a 1.13 × 10 −4 m mean diameter carbon-supported catalyst powder (ϱ p = 1000 kg/m 3 ) at a temperature of 573 K. Heat transfer coefficients are in the range h w = 231 to 366 W/(m 2 K) and are found to increase with increasing excess superficial gas velocity, yu o — u mf . Slug lengths are measured through application of a gamma radiation density gauge and are incorporated into the convective heat transfer model proposed by Xavier and Davidson [1]. Theoretically predicted bed-to-surface heat transfer coefficients h w are slightly higher than the experimentally determined values. These differences may be the result of limitations in estimating the effective characteristic vertical length L in the slugging bed. Within the limitations of the hydrodynamic measurements for estimating L, the Xavier and Davidson model provides a reasonable estimate of h w for the high pressure, slugging, hydrogen-fluidized bed described here.