Heat transfer mechanisms in gas fluidized beds. Part 3: Heat transfer in circulating fluidized beds

Abstract

This contribution presents the prediction of maximum heat transfer coefficients in bubbling fluidized beds, which takes into account thermal and fluid-dynamic properties of particulate material and fluidizing agent. The analysis suggests that heat transfer between heating or cooling surfaces and bubbling fluidized beds consists mainly in a particular manifestation of convective heat transfer. Another feature is an appropriate modelling of the particle convective component leading to a two-phase Prandtl number.

Acceleration of Load Changes by Controlling the Operating Parameters in CFB Co-Combustion

“…Figure 5 shows the relation between solids concentration from 1.1 to 8.03 m (splash zone and freeboard) and the heat transfer coefficient α CL . It is shown, that α CL strongly depends on the solids concentration in this area, which is consistent with the findings in literature also for large CFB boilers (Wu et al, 1987;Molerus and Mattmann, 1992;Wirth, 1995;Grace et al, 1997;Molerus and Wirth, 1997;Breitholtz et al, 2001;Oka, 2003;Dutta and Basu, 2004). As the entrainment increases, more particles get in contact with the heat exchanger surfaces.…”

Flexibility of CFB Combustion: An Investigation of Co-Combustion with Biomass and RDF at Part Load in Pilot Scale

“…The heat transfer to the cooling lances and the flue gas cooler is shown in Figure 7. The cooling lances take up the heat inside the reactor by particle convection and gas convection [14,15,52]. The dominant mechanism for the flue gas cooler is gas convection due to the low solid fraction in the flue gas.…”