Surface-to-bed heat transfer in fluidised beds of fine particles

This work reports experimental results on the heat transfer between a fluidised bed of fine particles and a submerged surface. Experiments have been carried out using different bed materials (polymers, ballotini, corundum, carborundum and quartz sand) with Archimedes number between 2 and 50. Dry air at ambient pressure and temperature has been used as fluidising gas. Three different exchange surfaces, namely a sphere and two cylinders with different base diameter and same height, have been used.Experimental results show that the heat transfer coefficient increases with particle Archimedes number and is almost independent from particle thermal conductivity for Kp/Kg > 30. Finally, the comparison of heat transfer coefficient for the different surfaces shows that the effect of the surface geometry may account for a 30% variation in the heat transfer coefficient, with higher differences occurring for coarser particles.

Graphical abstractExperiments on the heat transfer between with different shaped exchange surfaces and bed materials are reported. After comparison with data for coarser particles the maximum heat transfer coefficient results to be at Ar ~ 50 and the exchange surface shape may account for 30% variations of its value. Good experiments description are obtained with the A.P. Baskakov; B.V. Berg; O.K. Vitt; N.F. Filippovskii; V.A. Kirakosyan; M. Goldobin Yu; V.K. Maskaev, Heat transfer to objects immersed in fluidised beds. Powder Technology (1973), 8(5–6), 273–282 model.Figure optionsDownload full-size imageDownload as PowerPoint slide