The work described in this dissertation is concerned with some aspects of heat transfer in shallow gas fluidised beds. Results from the experimental investigations with the single heater indicated that fluidising velocity, particle size, bed height, heater diameter and heater position influence heat transfer. As expected, heater material has no influence. Unlike previous work, this work has concentrated upon the range of dependency of heat transfer on each of the tested parameters (e.g., heater diameter has no influence on heat transfer with heater diameter greater than 25.3 mm and bed depth has no influence on heat transfer for depths greater than 150 mm). The variation of this dependency with respect to the other parameters (e.g., influence of fluidising velocity on heat transfer coefficient increased with an increase in bed depth. The influence of heater location decreased with an increase in particle size, fluidising velocity and heater diameter), The effect of horizontal rod spacing on heat transfer was also examined, when unheated rods were used to complete the rod bundle. The effect of rod spacing was dependent on the other parameters (e.g., fluidising velocity, bed depth and heater diameter). Since the heat transfer depends primarily on frequent renewal of the particles at the heat transfer surface and particle mixing, these were improved by the use of gas jets. Heat transfer was found to increase by up to 50%. The following parameters were investigated: volumetric flow rate, particle size, heater size, bed height, jets position and direction and jets velocity to find their effect on the influence of gas jets on heat transfer. The data were compared with some earlier correlations and two dimensionless correlations developed. One was for a single heater and the other was for one row of horizontal rods. Unlike previous correlations, these correlations took account of both the effect of heater size and bed depth. The data for the single heater were compared with some earlier models and the fit with one of these models is good.
|Date of Award||1983|