A correlation for heat transfer between immersed surfaces and gas-fluidized beds of large particles

Abstract

Heat transfer between immersed surfaces and fluidized beds of large particles is investigated. Large particles here refer to those belonging to groups IIB and III of the powder classification scheme of Saxena and Ganzha, and characterized by Ar > 130,000. Four correlations for large particles proposed so far are examined on the basis of available experimental data. The data correspond to operating pressures ranging from ambient to 8.1 MPa and Reynolds numbers ranging up to 5000. A total of 366 data points have been used in the present study. It is found that none of the available correlations adequately predicts the heat transfer coefficient over the entire range of experimental conditions, and their ranges of applicability and probable uncertainties are established. A new correlation is developed on the basis of these data and the known mechanistic details of heat transfer by particle and gas convection. The proposed correlation is Nu = 5.95(1 − ε) 2 3 + 0.055 Ar 0.3 Re 0.2 Pr 1 3 and is accurate within ±35% for gas-solid fluidized bed systems characterized by Ar > 130,000.