Transferência de calor em leito fluidizado com tubos horizontais imersos

Abstract

In a bed of coal ash particles fluidized by air with ar without horizontal immersed tubes, the influence of such tubes on the expansion of the bed is examined and comparison is made between experirnent and the two-phase theory of fluidization. The expanison of the bed was determined experimentally employing low speed cine photography in arder to observe the fluctuations of bed height and the formation of bubbles at the bed surface. One of the immersed tubes is electrically heated; the temporal variation of temperature is observed as a function of the superficial velocity of gas; consequently measurements of the coefficient of global heat transfer were carried out. To explain the phenomenon of heat transfer, a model of the heat transfer mechanism is proposed, regarding that both the convective component of the discrete phase and continuous are affected by the fraction of heat transfer surface in contact with its respective phase.