Heat transfer coefficient profile around a horizontal cylinder immersed in a fluidised bed

This work reports experimental results on the local heat transfer coefficient on the surface of a horizontal cylinder immersed in a 500 µm glass beads bubbling fluidised bed . Experimental runs have been carried out at ambient pressure and temperature, with superficial velocity up to 0.45 m/s. The local value of the heat transfer coefficient has been determined with an angular shift of 10 deg. in order to derive a detailed profile of heat transfer rate around the cylindrical surface. Experimental results point out the occurrence of different heat transfer zones which directly reflect the existence of different hydrodynamic conditions around the cylindrical surface, previously observed by experimental (Buyevich et al. 1986) and numerical (Rong et al., 1999) studies. The highest value of the heat transfer coefficient is observed at the boundary of the lateral mixing and the upper sliding zone, as the result of a compromise between surface renewal frequency and particle concentration. Surface to bed voidage profile has been calculated from heat transfer coefficient measures by applying the Di Natale et al. (2008) model showing a good agreement with former studies and confirming the applicability of heat transfer data for the interpretation of fluid dynamic structure around surface immersed in fluidised beds.