Experimental study on gas–solid flow and heat transfer characteristics in downer moving bed

Abstract

As a special flow state of the downer, the downer moving bed has been applied in many fields. With the rapid development of the downer moving bed, experimental studies on the flow and heat transfer characteristics in the bed are urgently needed to promote the further development of it. Therefore, a complete set of downer moving bed experimental equipment is completed in this paper. Key parameters of flow characteristics such as void fraction and particle flow velocity are indirectly calculated through direct measurement of pressure and other data. The experimental results show that the factors affecting the solid circulation flow rate include bed inventory and inlet air velocity. Due to the high packing density of the particles, the void fraction of the downer moving bed has a small relative change. The particle flow velocity increases significantly with the increase of the inlet air velocity. Under the joint effect of particle velocity and void fraction, the variation of heat transfer coefficient along the height of the bed presents a single peak curve. And the heat transfer performance of the downer moving bed is obviously better than that of the downer fluidized bed at the same solid circulating flow rate. The differences between different tube bank arrangements and the single tube are compared. It is concluded that in practical applications, the requirements for heat transfer and heat transfer coefficient should be considered together and the best tube bank arrangement should be selected.