Heat transfer from fluidized beds to immersed fine wires

Abstract

Experiments were carried out to determine the heat-transfer coefficient between fluidized beds and immersed, loose, fine wires. The wires varied in diameter from 50 to 810 μm, and were made of Alumel, while the bed material consisted of uniformly sized sand, aluminum, polyethylene and glass beads, from 105 to 754 μm. Each wire was approximately 20 cm long, was totally immersed in a bed 14 cm ID, and was heated by an electric current. The current and voltage drop across the wire were measured independently and from these measurements the heat-transfer coefficient and wire temperature were determined. The results for large wire—small particle beds show that “h” is more than one order of magnitude above that for wires in air alone. For fine wire—large particle beds, “h” becomes smaller, approaching that for wires in air alone. Equation (8) is the final correlation for “h” as a function of wire size and bed properties.