不同翅片单元外颗粒流换热特性的数值研究

由于成本低,运行稳定,重力驱动移动床在高温固体散料余热回收领域应用潜力较大。然而,相关强化传热技术目前仍待完善。本文基于离散单元法,对颗粒流外掠翅片单元的流动换热特性进行了数值研究。研究表明:通过翅片增加换热面,可以显著提高传热量,但不同翅片单元外颗粒流传热特性不同。颗粒流与不同表面的换热,由颗粒更新、颗粒接触、颗粒竞争掺混以及表面面积共同决定。总体来说,在迎流区,倾斜平表面能扩大面积并确保颗粒更新,更有利于换热增强。而对于背流区,竞争掺混与颗粒接触的影响更大,采用圆弧表面更有优势。

Numerical Study on Heat Transfer Characteristic of Granular Flow Around Different Fin Elements

Due to the low cost and the stable operation condition,the gravity-driven moving bed has great application potentials in the waste heat recovery of hot solid granule.However,the relevant technology of heat transfer enhancement is still in advancing.In this work,discrete element method(DEM)was applied to investigate the heat transfer of granular flow around different fin elements.It was found that,the fin can increase the heat transfer area so that the heat transfer is significantly improved,while the detailed characteristics of granular flow will differ with the fin element.The heat transfer between the granular flow and different surfaces,is integrated by the particle update,the particle contact,the competitive particle mixing as well as the surface area.In general,in the upstream side,the inclined plane can increase the area with the relatively smooth flow.Therefore,it is more beneficial to improve the heat transfer.By contrast,the arc surface has more advantages in the downstream,because the particle contact and the competitive particle mixing will account for more roles here.