Entrance effect and gas-film mass-transfer coefficient in a large-diameterpacked column

The effects of the bed height and the entrance section below the packing su pport on mass transfer in a 1.2-m diameter packed bed of 50-mm ceramic Inta lox saddles were investigated under various gas flow rates from 1957 to 782 8 kg.h(-1).m(-2) and liquid flow rates from 12 200 to 46 700 kg.h(-1).m(-2) . The entrance effect accounted for 17% of the overall water vapor transfer red from moist air to a calcium chloride solution in the tower, regardless of the packing height. For a 0.91-m high bed, the average mass-transfer coe fficient was directly proportional to the gas rate and was proportional to the liquid rate to the power of 0.24. For a 1.8-m high bed, the average mas s-transfer coefficient was proportional to the gas rate to the power of 0.8 9 and appeared to be independent of the liquid rate. The height of a transf er unit (HTU) for 50-mm ceramic Intalox saddles remained relatively constan t under various gas rates used in the present study. The HTU was about 0.5 m for the short bed and 0.8 m for the tall bed.