Heat convection and radiation in flighted rotary kilns: A minimal model. (12th October 2016)

• Record Type: Journal Article
• Authors: Le Guen, Laurédan; Piton, Maxime; Hénaut, Quentin; Huchet, Florian; Richard, Patrick
• Is Part Of: Canadian journal of chemical engineering. Volume 95:Number 1(2017)
• Page Start: 100
• Page End: 110
• Publication Date: 2016-10-12
• Subjects: heat transfer -- Particle -- rotary kiln -- convection -- radiation -- granular materials; Chemical engineering -- Periodicals; Technology -- Periodicals; 660.05
• DOI: 10.1002/cjce.22659
• Languages: English
• ISSNs: 0008-4034

Abstract

Abstract: We propose a minimal model aiming to describe heat transfer between particles (i.e. grains) and gases in a model of flighted rotary kilns. It considers a channel in which a convective gas interacts with a granular suspension and a granular bed. Despite its simplicity it captures the main experimental findings in the case of dilute suspension of heavy grains typical of what can be observed in many industrial rotary kilns. Energy balance between each phase takes into account the main heat transfer mechanisms between the transverse granular motion and the convective gas. In the absence of radiation heat transfer, the model predicts exponential variations of the temperatures characterized by a length which depends on the granular and gas heat flow rates as well as on the exchange areas. When radiation is taken into account, the model can be solved numerically. For this case, the temperature variations can be fitted by stretched exponentials whose parameters are found to be independent of the studied phases. Finally, an efficiency criterion is proposed to optimize the length of the system. Abstract : A minimal model aiming to describe heat transfer between particles (i.e. grains) and gases in flighted rotary kilns is presented. It captures the spatial variations of the gas, grain, and wall temperatures. In the presence of radiation, those variations are well fitted by stretched exponential laws whose parameters (characteristic length λ and exponent β ) depend on fraction of grains α cg .