Heat transfer by liquid convection in particulate fluidized beds Scientific paper

Abstract

In this work the theoretical model for heat transfer from a wall to a liquid-solid fluidized bed by liquid convective mechanism has been proposed and developed. The model is based on thickness of boundary layer and film theory. The key parameter in the model is the distance between two adjacent particles which collide with the wall. According to the proposed model, the liquid convective heat transfer in a fluidized bed is 4 to 5 times more intense than in a single-phase flow. Additionally, the wall-to-bed heat transfer coef­fi­cient has been measured experimentally in water–glass particles fluidized bed, for different particle sizes. Comparison of the model prediction with expe­ri­mental data has shown that size of the particles strongly influences the mech­anism of heat transfer. For fine particles of 0.8 mm in diameter, the liquid con­vective heat transfer model represents adequately the experimental data, indi­cating that particle convective mechanism is negligible. For coarse particles of 1.5–2 mm in diameter, the liquid convective heat transfer mechanism accounts for 60 % of the overall heat transfer coefficient.