HEAT-TRANSFER AND DEFROSTING CHARACTERISTICS OF A HORIZONTAL ARRAY OFCOOLED TUBES IMMERSED IN A VERY SHALLOW FLUIDIZED-BED

Heat transfer and defrosting characteristics of a horizontal single-ro w array of cooled tubes immersed in a gas-solid fluidized bed, have be en studied experimentally. The fluidized bed produces gas-solid partic le impinging jets to effectively remove frost layers on the tube surfa ce. It has been verified that Frost-free running of the cooled tubes i s possible under the conditions of inlet air temperature - 7 degrees C , tube-surface temperature - 17 degrees C and relative humidity 80%. T he local contact frequency of particles onto the tube surface was meas ured by an optical sensing system and the defrosting mechanism of impi nging solid particles was observed in detail with a visualization tech nique. (C) 1997 Elsevier Science Ltd.