Design and analysis of compound structures integrated with bio-based phase change materials and lattices obtained through additive manufacturing

Phase change materials (PCMs) are an interesting category of materials employed in latent heat thermal energy storage, such as ad hoc designed heat exchangers. Nowadays, there are several typologies of PCMs, which derive from the wastes of the agricultural industry, which could be used for this kind of design. Each material made of biological waste has a different melting/solidification point and latent heat of fusion/solidification, which means flexibility of design on the heat exchangers by considering the different thermal proprieties of the chosen material. Also, using recycled material from wastes can lead to an overall improvement of the resources and goes hand in hand with the need of today's society to aim more and more at a Circular Economy. The industrial development of this kind of material is limited by its thermal properties, such as poor thermal conductivity both in liquid and solid phases, leading to low heat transfer effectiveness. To overcome these limitations, in this paper, the bio-based PCMs were integrated into a metallic reticular structure made of copper and aluminium and realised through Indirect-Additive Manufacturing, to improve the overall thermal conductivity of the system and increase the efficiency of the heat transfer. Four compound structures filled each time with four different PCMs were realised and tested, in order to thermally characterise each combination of materials used and choose which one has an overall better thermal behaviour. The results showed how the thermal storage/release was improved by 10% for the copper reticular structure, even if must be considered the tradeoff between better thermal management and the increase of the costs and the weight of the designed heat exchanger.