Investigating organic phase change behavior with thermal photography

The United Kingdom has a target of reducing fossil fuel emissions to 80% of 1990s emissions levels by 2050 and the National Grid is highly likely to see a vast portion of displaced currently fossil fuelled heating provision. There is therefore a significant need for research into alternatives to grid re-enforcement and additional power stations. Thermal energy storage systems present one such alternative via the decoupling of energy production and consumption in both industrial and domestic heating demand. Reversible phase change in materials such as paraffin waxes, inorganic salts and metal alloys represent such a technology. For these, the ability to empirically assess a given phase change is invaluable for determining materials of interest, system characteristics and optimisation of systems design in addition to quantitatively validate any given numerical system models.

In this work the development and evolution of the solid to liquid phase transition in two organic phase change materials: beeswax and paraffin wax is investigated. These are characterised via visible and thermal photography of an ongoing melt/solidification in a 5cm dimensioned cube constructed of several differing wall materials. Isothermal heat is supplied via the bottom surface by a laboratory hot plate.

During the melting and re-solidification process, the thermal conduction through non-infra-red transparent wall materials has been unable to indicate the solid-liquid interface or melt/solidification times. Direct infra-red transmission through the infra-red transparent materials and visible light analysis through the transparent walls has been able to provide a solid-liquid interface track and melting time to completion but is unable to confer any useful information during the solidification process due to premature solidification on the wall exposed to imaging.