Effects of solid particle properties on heat transfer between high-temperature gas fluidized bed and immersed surface

The effects of particle size, packed density, thermal conductivity and specific heat capacity on heat transfer between a high-temperature gas fluidized bed and an immersed surface are investigated. Hollow-corundum-sphere, corundum, magnesite and quartz sand particles with different diameters within the range of 0.35–1.21 mm are used. A liquefied petroleum gas fluidized bed furnace with 0.3 m × 0.3 m cross-section at hearth bottom and 0.8 m in height is used. The furnace temperature varies in the range of 990–1010 °C, the immersed object is a silver sphere of 20 mm in diameter and the fluidizing velocity is changed from about 1.0Umf (the minimum fluidizing velocity) to about 3.0Umf. The experimental results show that, for small particles, dp<0.8 mm, the effects of thermophysical properties of particles on heat transfer coefficient become important with particle diameter decreasing; for large particles, dp⩾0.8 mm, the effects of the properties on heat transfer are limited; and for all particles with diameters in the range of 0.35–1.21 mm, the heat transfer coefficient between the fluidized bed and the immersed surface is insensitive to particle thermal conductivity.