8. Heat transfer

Heat recovery in thermal CFLs is an important issue which, unlike in the case of bubbling fluidized beds, is not without its constraints. Indeed, the first problem encountered when installing a network of heat exchanger tubes inside the ascending bed is the disturbance it produces in the flow structure. What's more, given the high operating speeds of CFLs, the phenomenon of erosion makes it virtually impossible to use any network within the bed. Thus, the most realistic solution is to place the tubes along the wall of the ascending bed, where the flow is much slower. This solution seems all the more attractive as the bed has the full height to accommodate the tube network. Nonetheless, there remains an inescapable problem in the moderate velocity regimes of thermal CFLs: the curtain of particles falling close to the wall is rapidly cooled and screens the transfer between the central zone...