Effect of Aspect Ratio On the Melting Process of Carreau Non-Newtonian Phase Change Material in the Porous Space Between Two Vertical Pipes

In the current study using the enthalpy-porosity method, natural convection heat transfer in the melting process of Carreau non-Newtonian PCM was investigated in porous media within the space between two co-centric vertical cylinders. First, continuity, momentum and energy equations were developed for the non-Newtonian fluid melting process. Then to obtain a general pattern for  modeling the melting process, the aforementioned equations in the dimensionless mode were presented. To assure the accuracy of calculation, this study also controlled for the independency grid of the geometric model. To check for the validity, the results of this study were compared with prior studies. The results were expressed in the form of graphs of changes in melting volume fraction according to the change in Stephan number, Carreau index and porosity coefficient. The results showed that by increasing the aspect ratio from 0.5 to 2, Nusselt number and velocity increase but the velocity of melting decreases. The melting rate also increases with increasing Stefan number as well as decreasing porosity parameter. In addition, in a porous medium a change in the carreau index has no effect on the melting process rate.