Thermal entrance effect for heat transfer in up-flowing gas-particle suspensions

This paper presents an experimental investigation of thermal development for fully-developed gas-particle suspensions in a 0.161 m i.d. circulating fluidized bed. Results indicated that local heat-transfer coefficients at the lower and upper ends of the heat-transfer surface were higher than those in the middle. This effect was more significant with increasing suspension density but was insensitive to increasing superficial gas velocity and increasing temperature. Analysis suggests that thermal development at the lower end of the heat-transfer surface is caused by the convection of the up-flowing gas augmented by the presence of fine particles, while thermal development at the upper end of the heat-transfer surface is the result of the convection of downflowing particles near the riser wall.