The heat transfer characteristics in two (gas-liquid, liquid-solid) and three phase slurry(gas-solid-slurry phase) fluidized beds have been studied in 15.2 cm ID column.
In experiments air was used as gas phase and kerosene, kerosene-coal slurry and mineral oil-coal slurry were used as liquid phase and four different sized glass beads were employed throughout this study.
The effect of liquid velocity (3-12 cm/sec), gas velocity (0-12 cm/sec), slurry viscosity(1-28 cp) and particle size (1.7-8 mm) on heat transfer coefficient between the immersed electrical heater and the fluidized bed have been examined.
Individual phase holdups were measured by using a pressure profile methods.
In three phase slurry fluidized beds, liquid phase holdups increased but gas and solid phase holdups decreased with increasing liquid velocity. Bed porosities in three phase slurry fluidized beds increased with increasing gas velocity and were nearly independent on liquid viscosity.
In gas-liquid two phase flow system, heat transfer coefficient increased with increasing gas velocity.
In three phase slurry fluidized bed system, the heat transfer characteristics showed the characteristics of both gas-liquid and liquid fluidized system. Heat transfer coefficients increased with increasing gas flow rate and showed maximum value with respect to liquid velocity, and decreased with increasing liquid viscosity and generally increased with increasing particle diameter. Heat transfer coefficients in three phase slurry fluidized beds have been correlated as following.
$Nu_3 = 0.42 Fr^{-0.042}_1 Fr^{0.065}_g Re^{0.69}$
