Investigation of Polyamide 12 Powder Cooling Process under Natural Convection via Porous Medium, Non-porous Medium, and Experimental Approaches

Thermal issues in the selective laser sintering process have been one of the major concerns of researchers so far due to their vital importance to the mechanical properties of the final manufactured products. This paper is a numerical and experimental study in which the cool-down process of the PA12 powder is assessed using two different methods: a porous medium and a non-porous medium. Then, by comparing the numerical results with the experimental ones, the study aims to suggest the best method for simulating the heat transfer in PA12 powder. Moreover, after approving the method of simulation, using this method, the powder cool-down process under natural convection from around the construction temperature (170 °C) to a temperature close to the ambient temperature (27 °C) is simulated by considering both the powder and the ambient gas for four different gases (air, nitrogen, argon, and helium) aiming to assess the heat transfer coefficient for each of the scenarios. The paper's main findings include: first, the non-porous medium point of view outperforms the porous medium; second, four different formulas are proposed for the natural convective heat transfer coefficient of PA12 and each of the studied gases.