The present study explores the process of melting of a phase change material (PCM) in a vertical circular tube. A detailed analysis of the digital experimental pictures, obtained in previous investigations, is performed. In this analysis, the tubes are subdivided by horizontal planes into 1cm high slices. The melt fraction as a function of time is calculated separately for each slice, yielding the local heat transfer rates into the solid. The flow patterns that cause these effects are obtained from the numerical simulation. The simulation provides a detailed heat flux distribution on the inner wall of the tube. The numerical simulations, performed using the Fluent 6 software, model the same commercially available paraffin-type material that was used in the previous experimental investigations.. The simulation results, along with the analysis of the experimental pictures, reveal the effects of convection in the liquid phase, which make heat transfer from the wall to the melting PCM essentially non-radial. Thus, the analysis adopted in the present study provides a comprehensive picture of melting in vertical circular tubes at various locations and instants.

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