Mitigation of ice crystallization fouling in stationary and circulating liquid-solid fluidized bed heat exchangers

Liquid-solid fluidized bed heat exchangers are attractive ice crystallizers since they are able to mitigate ice crystallization fouling and exhibit high heat transfer coefficients. Experiments show that the fouling removal ability of stationary fluidized beds increases with decreasing bed voidage (95-80%) and increasing particle size (2-4 mm). The removal of ice crystallization fouling appears to be more effective in circulating fluidized beds, especially at high circulation rates. Fouling removal is realized by both particle-wall collisions and pressure fronts induced by particle-particle collisions. A comparison between ice crystallization experiments and impact characteristics shows that the removal rate is proportional to the impulse exerted on the wall. A model based on these phenomena is discussed and predicts the transition temperature difference for ice crystallization fouling in both stationary and circulating fluidized beds with an average absolute error of 9.2%. (C) 2009 Elsevier Ltd. All rights reserved.