極浅層流動層中におかれた水平冷却管群の伝熱と除霜特性に関する研究

抄録

Heat transfer and defrosting characteristics of a horizontal single-row array of cooled tubes immersed in a gas-solid fluidized bed have been studied experimentally. The test fluidized bed with a low static bed height of l0mm produced excellent fluidization and effective gas-solid particle impinging jets for defrosting through the use of a newly developed cornice-type multislit distributor, in spite of very low pressure loss. The measured local heat-transfer coefficients and their transient behavior were discussed by consideration and comparison with these defrosting mechanisms. The defrosting limit when utilizing the present fluidized bed was also examined. It has been verified that frost-free running of the cooled tubes is possible with the use of this fluidized bed system under the conditions of inlet air temperature of -7°C, tube-surface temperature of -17°C, and relative humidity of 80%. Local contact frequency of particles onto the tube surface was measured by an optical sensing system and the defrosting mechanism of impinging solid particles was observed in detail by a visualization technique.