A comparative study of thermal behaviour of a horizontal and vertical shell-and-tube energy storage using phase change materials

In this paper, thermal behaviour in a vertical and horizontal shell-and-tube energy storage system using phase change materials (PCMs) is investigated and compared using a combined conduction and convection heat transfer model. The model is first evaluated using published experimental data available in the literature and then used to study the temperature variation, solid–liquid interface, phase distribution, total melting and solidification time during the charging and discharging processes of PCMs. The simulated results show that during the charging process for the horizontal orientation, convective heat transfer has a strong effect on melting of the upper part of the solid PCM and is less significant during melting of the lower half of the solid PCM. However, in the vertical orientation, convective heat transfer is the same active during the entire charging process. In the discharging process, the thermal behaviour does not show any difference between horizontal and vertical systems. The results indicate that the horizontal orientation has superior thermal performance during the charging and in particular during part-load energy charging. The results also show that increasing the hot heat transfer fluid (HTF) inlet temperature substantially reduces the total charging time for both orientations. However, increasing the flow rate does not greatly affect the charging and discharging processes.