Investigation of the melting process of polyethylene glycol 1500 (PEG 1500) in a rectagular enclosure

Abstract The melting process of polyethylene glycol 1500 (PEG 1500) adjacent to a hot vertical wall in a rectangular enclosure is investigated experimentally. Polyethylene glycol 1500 was selected because its melting temperature is >44 °C making it a suitable candidate as lagging material to prevent wax deposition and hydrate formation in subsea oil pipelines. A new apparatus cell consisting of a rectangular cell 200 × 200 × 180 mm split equally into three chambers by two, 2 mm thick, aluminium plates was constructed. Each end chamber was supplied with hot and cold water respectively. The centre chamber was filled with PEG1500. Thermocouples and an infrared camera were used to measure the temperature at different locations inside and on the surface of the phase change material (PCM). The temperature contours, percentage (%) of melting and the melt front evolution are presented for various operating conditions. A dye tracer solution was used to show the natural circulation of the PCM as it melted. Results indicate that during the initial stage of melting heat conduction is the dominating mode of heat transfer, followed by transition from conduction to convection regime and convection dominating heat transfer regime. The results show a strong correlation between the hot wall temperature and the fraction melt as it control the convection heat transfer. In contrast, the results also show that cold wall temperature have insignificant effect on fraction of PCM melt with the time for constant hot wall temperature and the melt rate has a same characteristic shape for all cold wall temperatures used in this study. A dye tracer study shows the natural circulation in the liquid zone, confirm the presence of the strongest convection at the solid-liquid interface and reveal the velocity profile/current direction. An approximate time of six minutes was recorded for the circulation of the solution round the enclosure giving approximate velocity of 0.00117 m/s.