Thermal conductivity enhancement of hydrated salt phase change materials employing copper foam as the supporting material

Thermal conductivity is a crucial factor for selecting appropriate phase change material (PCM) for use in the field of thermal storage. In the current work, sodium acetate trihydrate (SAT) was combined with xanthan gum and copper foam to prepare a composite PCM using a vacuum impregnation method, with the main purpose of increasing its thermal conductivity. The latent heat of SAT/xanthan gum (SAT/X) containing 98 wt% SAT and 2 wt% xanthan gum was measured to be 255.5 J/g, close to the theoretical value according to the content of SAT in the composite SAT/X. The saturated mass fraction of SAT/X in SAT/xanthan gum/copper foam (SAT/X/CF) was calculated to be equal to 77.2%, therefore the SAT/X/CF can have an estimated latent heat of 197.2 J/g. The thermal conductivity of final composite PCM was 2.10 W/(m.K), 1.76 times higher than that of SAT/X, suggesting that copper foam performs well in the area of thermal conductivity enhancement. A heating/cooling cycle was carried out 200 times to examine the cycling stability of SAT/X and SAT/X/CF. The experimental analysis illustrated that the latent heat of SAT/X decreased by only 5.9%, as compared with that of the prepared one. Improved thermal conductivity, high heat storage capacity together with great thermal cycling stability make SAT/X/CF a very promising material in solar thermal energy storage.