Effect of anionic, cationic and non-ionic surfactants on graphene nanoplatelet enhanced organic phase change material: A comparative thermal performance evaluation

Abstract

Phase change materials (PCM)s is the predominant substance that facilitates thermal energy storage (TES) in the form of latent heat. PCMs stores and releases thermal energy during phase transition, making it expedient to manage temperature fluctuation in TES systems. However, the application of PCMs in various industrial fields is limited due to their low thermal conductivity and low melting enthalpy. The inclusion of thermally conductive nano-fillers resolves the issue of low thermal conductance of PCMs. However, the effectiveness of nano-fillers inclusion is subjected to uniform dispersion without any agglomeration. Surfactants is required to enhance the overall effectiveness and performance of PCM nano composites by preventing phase separation and preserving the stability of the nano-filler that are dispersed in PCM matrix. RT44HC of organic PCM is selected has the advantage of high melting enthalpy (250 J/g) on the contrary suffers from poor thermal conductivity. Herein, this research investigates the thermal performance of graphene nanoplatelets (GNP) nano-filler dispersed in RT44HC with anionic, cationic, and non-ionic surfactants to evaluate their performance in overcoming the issue of agglomeration. In this regard, four surfactants: sodium dodecyl benzene sulfonate (SDBS) as an anionic surfactant, cetyl tri-methyl ammonium bromide (CTAB) as a cationic surfactant, Tween 60 and gum Arabic as a non-ionic surfactant were investigated at varied weight fractions of 0.5 %, 0.7 %, and 1.0 % equivalent to that of nano-filler. A two-step synthesis with extensive ultrasonication was applied to reach a homogeneous mixture. The result shows that utilising GNP and SDBS surfactant in RT44HC demonstrates 103.33 % increase in thermal conductivity of PCM from 0.210 W/(m·K) to 0.427 W/(m·K). The improvement in thermal conductivity owing to well-developed thermal network channels facilitating thermal conductance. The melting enthalpy of RT44HC does not affect severely as it reduces 3.63 % for the optimum thermal conductivity nanocomposite. Furthermore, UV–Vis results were tremendous, as GNP lowered the light transmittance from 94.19 % to 17.77 %, indicates high absorbance capability. After 500 thermal cycles, the melting enthalpy remains stable within ±7.5 % uncertainty, indicating that the composite is reliable for long-term performance. Research highlights the RT44HC/GNP composite, with surfactant enhancement, as a promising candidate for medium-temperature solar thermal applications.