Experimental and numerical study on pressure drop and heat transfer performance of grille-sphere composite structured packed bed

Packed beds are widely used in industries, in which the flow and heat transfer characteristics of the packed bed may have a significant effect on the energy efficiency of the whole system. The flow and heat transfer characteristics of packed beds are greatly dependent on their structures. Therefore, it is crucial to develop new packing structures to improve the overall heat transfer performance of packed beds. In the present paper, a grille-sphere composite structured packed bed (GSCSPB) was developed. The new structure aims at overcoming the shortcomings of both randomly packed beds and traditional structured packed beds. A naphthalene sublimation experiment is conducted to measure the pressure drop and heat transfer in GSCSPB and evaluations of the comprehensive heat transfer performance are made to compare the GSCSPB with the randomly packed bed and structured packed bed. A 3-D model is set up to analyze the mechanism of the heat transfer enhancement by using FLUENT 14.0. Results show that firstly, GSCSPB has an excellent design property to reduce the pressure drop of the randomly packed bed and enhance the heat transfer of the structured packed bed, obtaining the highest overall heat transfer performance among the compared packed beds. Secondly, it demonstrates that the existence of the grille wall can change the velocity and temperature distributions, thus the heat transfer is enhanced in GSCSPB compared with a similar configuration without the grille. Finally, it indicates that the grille will help to design a new packing configuration which could achieve a structured packed bed easily and improve the overall heat transfer efficiency.