Heat transfer to small cylinders immersed in a packed bed

Fluidized beds have seen increasing use for heat-treating steel wires as an environmentally friendly alternative to molten lead heat-treating systems. System upsets can result in defluidization (packed bed condition) in all or portions of the bed, affecting heat transfer rates to the wires. Existing information regarding heat transfer to cylinders in a packed bed is sparse and contradictory when applied to small cylinder sizes appropriate to wire (1–10 mm). This study examines heat transfer to cylinders immersed in packed beds in size ranges appropriate to steel wire heat-treating applications. An appropriate correlation is developed and presented.