Heat transfer characteristics around an elliptic heated tube immersed in fluidized bed were studied experimentally. Experiments were carried out under uniform heat flux condition, with air as a fluidizing gas and pulverized coal as a bed material of Geldart D. An elliptic tube was heated by using a cartridge heater of 16 mm OD and 200 mm length. The heated tube had a total surface area of As ≈ 0.015 m2, and length of 200 mm. The local as well as average heat transfer coefficients were calculated at different superficial air velocities, particles sizes of 2, 4 and 6 mm, and static bed height of 250 mm. Various values of fluidization number, Usup/Umf, based on hydraulic diameter of the heated tube are utilized in the experiments which are ranged from 1 to 1.4. The results showed that, the minimum fluidization velocity increased with the increase in bed particles diameter. The local Nusselt number was quasi-uniform and having a maximum value at the sides of the heated tube and minimum at the stagnation, ϑ=0°, and top, ϑ=180°, of the tube. The local and average Nusselt numbers increase with the increase of the fluidization velocity and decrease in particles diameter.

In the present work, heat transfer characteristics and flow field from a heated elliptic cylinder immersed in fluidized bed is studied numerically using CFD package. The flow pattern and heat transfer fields around the heated cylinder is predicted using a two fluid Eulerian-Eulerian model coupled with kinetic theory of granular flow (KTGF) with heat transfer. Experiments were carried out under uniform heat flux condition, with air as a fluidizing gas and pulverized coal as a bed material. The Reynolds number based on the equivalent hydraulic diameter, Dh, was ranged from 941to 1263. The simulation results of the present study showed that, for the range of gas velocity considered, at minimum fluidization velocity, Re = 914, the Nuθ is maximum at the sides of the cylinder and minimum at the stagnation, θ=0o, and top, θ=180o, of the cylinder. The average Nusselt number for the elliptic cylinder increases with the increase of the fluidization velocity. The present data is compared with a previous well-known correlation from the literature for a circular cylinder and a reasonable deviation about 11-30% is found.

In the present work, numerical simulations are performed to study heat transfer characteristics and fluid flow around elliptic tube heat exchanger. The results for heat transfer coefficient between immersed inline and staggered bundles of horizontal smooth tubes and air-fluidized bed of pulverized coal, dp = 2 mm, are reported within the range of fluidization number, Usup/ Umf, ranges from 1 to 1.4. Heat transfer as well as multiphase flow dynamics in fluidized bed is modelled using the Eulerian-Eulerian and the Two-Fluid Model (TFM) with Kinetic Theory of Granular Flow (KTGF) to describe the granular flow characteristics of the solid phase. The average heat transfer coefficient for the present work is compared with that obtained from the well-known correlation of circular cylinder and a noticed improvement is observed. It is noticed that, the average Nusselt number increases with fluidization number. Also, it is noticed that, the average Nusselt number in case of staggered tubes bundle is higher than the case of inline tubes bundle. The inline tube bundle has lesser pressure drop than the staggered tube bundle.