Conjugated non-Newtonian phase change process in a shell and tube heat exchanger: A parametric-geometric analysis

Abstract

The present study aims to better knowledge of the phase change process in shell and tube heat exchangers in the presence of thick tubes, porous medium, and Carreau- Yasuda non-Newtonian fluid. It is the first time that this combination has been presented in the literature. It is believed that considering the phase change process of RT-35 as a Carreau-Yasuda non-Newtonian one in the presence of porous medium and copper pipes can create a challenge in the field. The continuity and momentum equations along with the horizontal and vertical directions, the heat equation for RT-35 as a non-Newtonian Carreau–Yasuda fluid, and the heat equation for thick tubes were determined and transformed into their non-dimensional forms, which were then solved using the finite element method. The effects of non-dimensional numbers such as Stefan number, porosity parameter, Rayleigh number, and Effect of rheological behavior of fluid have been determined. Reaching better performance via using porous medium and center- a to- center distance of double pipes, as well as a number of the pipes, are the ideas to conduct the present study. The results were reported as the average Nusselt number, melting fraction of the PCM, the average velocity of the non-Newtonian fluid, streamlines, and isotherms, all as functions of non-dimensional time. The results indicated that higher values for the porosity parameter led to lower heat transfer rates, which in turn weakened the PCM melting front. It was also found that changing the center-to-center distance between the hot tubes influenced melting front propagation.