Abstract
In the present paper, the heat transfer of gravity-driven dense particle flow around five different shapes of tubes is numerically studied using discrete element method (DEM). The velocity vector, particle contact number, particle contact time and heat transfer coefficient of particle flow at different particle zones around the tube are carefully analyzed. The results show that the effect of tube shape on the particle flow at both upstream and downstream regions of different tubes are remarkable. A particle stagnation zone and particle cavity zone are formed at the upstream and downstream regions of all the tubes. Both the stagnation and cavity zones for the circular tube are the largest, and they are the smallest for the elliptical tube. As the particle outlet velocity (vout) changes from 0.5 mm/s to 8 mm/s at dp = 1.72 mm/s, when compared with the circular tube, the heat transfer coefficient of particle flow for the elliptical tube and flat elliptical tube can increase by 20.3% and 15.0% on average, respectively. The proper design of the downstream shape of the tube can improve the overall heat transfer performance more efficiently. The heat transfer coefficient will increase as particle diameter decreases.
Highlights
In the recent years, the world’s energy and environmental problems have become more and more prominent, which makes it urgent to improve energy efficiency and develop sustainable energy techniques
This shows that the effect of tube shape on the particle flow at both upstream velocity vector distributions of particle flowing around different It tubes at a certain are
It is noted that, at the downstream region (Zone 3) of different tubes, a particle cavity zone is formed, where particles are almost untouched on the tube wall
Summary
The world’s energy and environmental problems have become more and more prominent, which makes it urgent to improve energy efficiency and develop sustainable energy techniques. For the MBHE, the granular flow inside is driven by the gravity, and the heat transfer is relatively lower [6]. It is important to improve the heat transfer of particle flow in the MBHE. The type of heat transfer element in the MBHE may include horizontal tubes, vertical tubes and parallel plates. For the MBHE with vertical tubes [9] or parallel plates inside [10], the solid particles move vertically along the tubes or palates without fully mixing, which would limit the heat transfer of particle flow along the tubes or plates in the MBHE. The particle flow around a horizontal tube should be disordered and fully mixed [11], and the heat transfer around the horizontal tube should be better. Many researchers have studied the effects of particle material, particle size, particle
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