Heat transfer studies from single cylinder and tube bundle in fluidized bed

It was observed that at flow rates in the range of incipient fluidization, the onset of fluidization occurs at the tube sides, with a corresponding increase in local heat transfer coefficient in that region. As the fluidization velocity increases the activity near the defluidized cap at the top of the cylinder becomes more intense, with a consequent large increase in the local heat transfer coefficient in this region when compared to that in other regions. The average heat transfer coefficient based on the local values around the circumference was observed to increase with fluidization velocity for the range of particle sizes and types used in the investigation. Such an increase becomes more pronouned with increasing pitch-to-diameter ratios, levelling off at a value of the ratio of about 1.7. An empirical correlation together with an additional correction factor for the influence of the pitch-to-diameter ratio, are proposed.