A particle-laden flow inside solid gas cyclones has been studied using computational fluid dynamics (CFD). The effects of high temperatures and different particle loadings have been investigated. The Reynolds stress (RSM) model-predicted results, in the case of pure gas, are within engineering accuracy even at high temperatures. Using the granular mixture model for the cases of particle-laden flow, discrepancies occurred at relatively high loadings (up to 0.5？kg/m3). Since the pressure drop is strongly related to the friction inside the cyclone body, the concept of entropy generation has been employed to detect regions of high frictional effects. Friction has been observed to be important at the vortex finder wall, the bottom of the conical-part wall, and the interface separating the outer and the core streams. The discrepancies between the present numerical simulation and the experimental results taken from the existing literature, which are caused by the mixture and turbulence models simplifying assumptions, are discussed in this paper. 1. Introduction Solid gas cyclone separators are known to have low cost, they are easy to operate, simple to manufacture, and relatively easy to maintain because of lack of moving parts. This has made them the best devices used in industries where the separation of solid particles from a gaseous phase is crucial. Cyclone separators are used in several industrial applications such as cement industry, pressurized fluidized bed combustors, and fluidized catalytic cracking processes. The highly swirling flow generated inside the cyclone causes the particles to be ejected under the effect of the centrifugal force towards the outer wall. On the other hand, the generation of high swirl intensities requires high energy consumption (high pressure drop) [1–3]. The design of cyclones involves thus two conflicting and simultaneous requirements of minimizing the pressure drop and maximizing the separation efficiency. The pressure drop and separation efficiency are thus important for successful design and need to be predicted with the required engineering accuracy. Theoretical studies have established semiempirical models for the prediction of single-phase pressure drop [4–6]. The main parameters used are the geometry of the cyclone and a characteristic tangential velocity component. The single-phase reasoning has been developed to take into account the effects of the solid loading and the temperature. The influence of temperature is introduced via the density and viscosity in the Reynolds number while the loading effect is usually
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