HEAT TRANSFER WITH A MOVING BOUNDARY - APPLICATION TO FLUIDIZED-BED COATING

This study presents a theoretical relationship between coating thickness on an object immersed in a fluidized bed of coating material and the physical properties of the system. The theory of fluidized bed coating was developed using the heat-balance integral in solving the problem of heat-conduction with a moving boundary as applied for the coating film. In developing the theory, the temperature profile within the coating film was represented by a second-degree polynomial. The theoretical solution was compared with experimental data given in the literature. The agreement is good. On the average, the theory predicts coating thicknesses that are higher than the experimental ones by about 10 per cent. This deviation is attributed mainly to the assumption of constant object and coating film temperature made in the theory. The heat-transfer coefficient is a major factor in the fluidized bed coating process. Coating data reported in the literature do not generally give the heat-transfer coefficient in the fluidized bed. A graphical method for estimating the heat-transfer coefficient was developed for experiments where final thickness data are reported. © 1969.