**2. Physical Model**

The slurry is assumed to be a mixture of fine solid particles and water, which plays the role of a carrier liquid. The assumptions made in the physical model are as follows:


For simulation purposes, the cylindrical coordinate system is used, where 'ox' is the main flow direction, while 'or' is the radial coordinate, as presented in Figure 1. It is assumed that the wall temperature is equal to Tw = 293.15 K, and the heat flux density q = −500 W/m and both quantities are steady. Simulations are performed for carrier liquid flow (C = 0%) and for slurry with a solid particle density equal to 2550 kg/m3, solid concentrations 10%, 20%, 30% and for an inner pipe diameter D = 0.02 m.

**Figure 1.** The cylindrical coordinate system used for numerical predictions.
