**ABSTRACT**

In this paper a numerical simulation of the melting process of Carreau non-Newtonian phase change material inside two porous vertical concentric cylinders included constant temperatures of the inner and outer walls, represented by Th and Tc, respectively. Half of the void between the two pipes is filled with copper porous media and paraffin wax as a phase change material. The governing equations are converted into a dimensionless form and are solved using the finite element method. The enthalpy porosity theory is applied to simulate the phase change of phase change material while the porous media follow to the Darcy law. Outcomes are shown and compared in terms of the streamline, isotherm, melting fraction and mean Nusselt numbers. The solid liquid interface location and the temperature distribution are predicted to describe the melting process. The effects of the Carreau index, porosity and non-dimensional parameters such as Stefan number, Darcy number, and Rayleigh number are analyzed. Our results indicate a good agreement between this study and the previous investigations. The results show that an increase in Rayleigh number, Stefan number, and Darcy number, increases the melting volume fraction and reduces the melting time. Also, the time of melting non-Newtonian phase change material decreases when Carreau index and porosity decrease.

**KEYWORDS**

PAPER SUBMITTED: 2020-07-11

PAPER REVISED: 2020-10-02

PAPER ACCEPTED: 2020-10-05

PUBLISHED ONLINE: 2020-11-07

**THERMAL SCIENCE** YEAR

**2021**, VOLUME

**25**, ISSUE

**Issue 6**, PAGES [4283 - 4293]

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