HEAT-TRANSFER IN FLUIDIZED-BED COATING OF COPPER CYLINDERS

An experimental investigation of heat transfer of copper cylinders of different diameters immersed horizontally in a fluidized bed coating process was conducted with a commercially available thermoplastic paint powder. The minimum fluidization velocity was determined to be 0.012 m/s and found to agree well with theoretical prediction. Transient temperature profiles measured over the duration of immersion were found to be in agreement with the lumped capacitance model which assumes a constant heat transfer coefficient during the coating process. The temperature drop was found to be smaller for larger specimens and higher flowrates. Measurements using a microscopic image analyzer indicate that the coating thickness increases with the initial specimen temperature, specimen size, air flowrate and immersion time.