**4. Conclusions**

This paper presented a numerical investigation into the impacts of melting on the convective flow of phase change materials within cylindrical tubes containing cross-shape heated sections. Four cases were considered based on the number of heated wings, namely, case 1 (two horizontal wings), case 2 (two vertical wings), case 3 (four wings), and case 4 (eight heated wings). The unsteady case was considered and completely melted conditions were assumed. The finite element method (FEM) with the Poisson pressure equation was applied to solve the governing system. The following are our major findings:


**Author Contributions:** Conceptualization, S.E.A. and A.A.; methodology, A.A.; software, A.A.; validation, W.K.H., R.A.A. and A.A.; formal analysis, O.Y., and S.A; investigation, S.E.A.; resources, A.A.; data curation, S.A.; writing—original draft preparation, S.A.; writing—review and editing, W.K.H., R.A.A., and O.Y.; visualization, W.K.H.; supervision, A.A.; project administration, A.A.; funding acquisition, S.A. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research work did not receive any funds.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** All data are available upon request from any of the authors.

**Conflicts of Interest:** The authors declare no conflict of interest.
