Forced convective heat transfer in novel structured packed beds of particles

Abstract

Paper presented at the 8th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Mauritius, 11-13 July, 2011.Randomly packed beds are widely used in a variety of industries, because of their low cost and ease of use compared with other packing methods. However, the pressure drops in such packed beds are usually much higher than those in other packings, and the overall heat transfer performances may be greatly lowered. In order to reduce the pressure drops and improve the overall heat transfer performances of packed beds, structured packings are considered to be promising choices. In this paper, some of our recent contributions on the hydrodynamic and heat transfer characteristics in some novel structured packed beds are introduced, where the effects of packing form and particle shape are carefully investigated, and the numerical and experimental results are also compared in detail. Firstly, it is found that, with proper selection of packing form and particle shape, the pressure drops in the structured packed beds can be greatly reduced and the overall heat transfer performances will be improved. The traditional correlations of flow and heat transfer extracted from random packings are found to overpredict the pressure drops and Nusselt numbers for all the structured packings, and some modified correlations are obtained. Secondly, it is revealed that, both the effects of packing form and particle shape are significant on the flow and heat transfer in structured packed beds. With the same particle shape (sphere), the overall heat transfer efficiency of SC packing is the highest. With the same packing form, such as FCC or SC packings, the overall heat transfer performance of ellipsoidal particle model is better. Furthermore, with the same particle shape and packing form, such as BCC packing with spheres, the overall heat transfer efficiency of uniform packing is higher than that of non-uniform packing.