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
Herein, hydrodynamic analysis from a large-eddy simulation in Couette–Taylor–Poiseuille (CTP) geometry is numerically investigated. The present geometry is inspired by a previous experimental work in which heat transport phenomena were investigated in a heat recovery system devoted to a rotary kiln facility. The streamwise and spanwise components of the velocity and the Reynolds stress tensor are firstly validated using an experimental benchmark. The effect of the axial flow rates is studied at a fixed rotational velocity. It is shown that the streamwise velocity component damps the vortex flow organization known in Couette–Taylor (CT) flow. The bulk region and its wall footprint are therefore characterized by various methods (spectral and statistical analysis, Q-criterion). It is shown that the turbulent kinetic energy of the streamwise component in the near-wall region is augmented leading to a multi-scale nature of turbulence.
Heat transport in rotating processes finds a wide range of application in which academic issues in the fluid mechanics and heat transfer areas are here reported. This paper discusses successive works from the seminal paper of Taylor (1923) to recent numerical results established from a broad range of methods such as DNS, LES, RANS or LB methods. The flow regimes identification is thus reported in Taylor–Couette geometry. The role of the axial flow rates in the apparition, stabilization and destruction of the large-scale of the turbulent structures is depicted in the case of Taylor–Couette–Poiseuille geometry. In a non-isothermal condition, a discussion is held on the various exponent values found in the scaling relationships relying on the Nusselt number as a function of the Rayleigh or Reynolds numbers according to the regimes of thermal convection.
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