Numerical Study of Heat Transfer in Gravity-Driven Particle Flow around Tubes with Different Shapes

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.

Numerical Investigation of Gravity-Driven Granular Flow around the Vertical Plate: Effect of Pin-Fin and Oscillation on the Heat Transfer

“…Compared with the continuous method, the discrete method can calculate the detailed motion of each particle. Nowadays, it has been widely used in the study of particle flow and heat transfer, such as moving bed [13], packed bed [28] and screw reactor [29].…”

“…(5) The physical properties of the particles and the gas are kept constant. More details on particle heat transfer model and model verification can be found in the work of Tian et al [13].…”

“…Particles exchange heat with horizontal tubes [10] or vertical plates [11] arranged in the heat exchanger. For horizontal tubes, Dai et al [12] found that a stagnation zone would form at the upstream region of the tube and a cavity zone would form at the downstream region of the tube by experiment, which would seriously affect the flow and heat transfer of particles [13]. Bartsch et al [14] described these two zones by numerical simulation and verified the simulation results by experiment.…”

“…Oscillation can significantly improve the heat transfer coefficient. Tian et al [13] studied the heat transfer of particles flow around the circular tube, the elliptical tube and the flat elliptical tube by discrete element method and found that the shape of the tube had a significant effect on the particle flow at the upstream and downstream of different tubes. The elliptical tube had the smallest stagnation zone and cavity zone, and its heat transfer coefficient was highest.…”

Emerging Tools for Energy System Design Increasing Economic and Environmental Sustainability

“…One of the measures to increase energy efficiency is to improve heat transfer between fluids in heat exchanger units. The authors of the next paper, Tian et al [92], entitled "Numerical Study of Heat Transfer in Gravity-Driven Particle Flow around Tubes with Different Shapes", investigated the mechanism of heat transfer in moving bed heat exchangers, in which heat transfer takes place between the solid particle stream and the fluid. This type of heat exchanger is widely used in energy-intensive industries.…”