This paper presents a novel method of heat transfer enhancement and melting process expedition of phase change materials (PCMs) via silicone oil for the application in thermal energy storage systems. Sudden spot heating/cooling of the PCM causes a non-uniform melting process and in some cases the volume expansion/contraction. To avoid this malfunction, silicone oil can be applied in these systems to increase convective heat transfer (stirring effect). The feasibility of this method is investigated by two experimental analysis, one by having the mixture in a cylindrical container and one in a cubic container. The results from the images taken by Charge-Coupled Device (CCD) camera in the first analysis show a uniform melting process of the PCM. In the second analysis, the comparison is made for the two parallel setups with and without the silicone oil with the same operating conditions. The results show that in the system that lacks silicone oil, the paraffin starts melting after around 11 minutes from the heater start-up, while this time is around 6 minutes in the system with silicone oil. The effectiveness of silicone oil in enhancing the heat transfer rate is shown by a temperature rise of around 10 °C in the container. Applying PCMs in conjunction with silicone oil in various thermal storage systems for heating/cooling applications specifically in solar thermal collectors, enables heat transfer enhancement and consequently heat storage directly on the system.
Heat Transfer Enhancement in Direct Contact Melting Process.
