Particle migration at solid surfaces and heat transfer in bubbling fluidized beds. II: Prediction of heat transfer in bubbling fluidized beds

In a gas fluidized bed, heat to and from a heat exchanger surface can be transferred by the gas and/or particle convection. Despite more than 40 years of intensive research on this topic, the contribution through particle convection remains inadequately described, while the gas convective component has been straightforward to predict. In Part 1 of this paper, the pulsed light method of tracing particles in a fluidized bed close to a wall has been introduced, allowing a better understanding of how particle convective heat transfer works. In Part 2, a correlation is proposed, which allows prediction of the heat transfer coefficient in dependence of the superficial gas velocity. The correctness of the prediction is tested by comparison with more than 20 measurements covering the following range of system data and operational conditions: particle size 74–4000 μm particle density 26-11,800 kg m−3 gas pressure 0.03-2 MPa bed temperature 290–1050 K excess gas velocities up to 2.5 ms−1. In the investigated temperature range of 290–1050 K there appears to be no significant contribution to the heat transfer due to radiation.