Abstract
The aim of this study is to prepare a novel form-stable phase-change material (PCM), palmitic acid-stearic acid/expanded graphite (PA-SA/EG) PCM, for latent heat thermal energy. A eutectic mixture of palmitic acid and stearic acid is incorporated with expanded graphite (EG). The thermal properties and microstructure of the novel PCMs were studied. The optimal mass ratio of PA-SA in composite PCM is approximately 92.8%. DSC results showed that the novel PCMs had suitable phase-change temperature (Tm: 55.18°C, Tf: 54.91°C) and high latent heat (Hm: 176.2 J/g, Hf: 175.6 J/g), and good thermal performance was maintained after 1500 times thermal cycling. The PA-SA binary eutectic mixture was uniformly distributed in the porous structure of EG, and the PCM did not leak even in molten state. EG had little effect on the thermal properties of the PA-SA binary eutectic mixture and remarkably improved the thermal conductivity of the composite PCMs. TGA test indicated that the composite PCM had nice thermostability in the range of operating temperature. Based on all these results, the PA-SA/EG composite PCM is a promising material for low-temperature thermal energy storage applications.
Highlights
Phase-change materials can store or release thermal energy during phase transition [1]
All the results showed that the porous structure of expanded graphite (EG) allowed the uniform distribution of PA-SA and greatly enhanced the thermal conductivity, heat storage, and heat release rate of the PA-SA/EG composite phase-change material (PCM)
The addition of EG into PA-SA resulted in a remarkable improvement in the thermal conductivity, which was verified by comparing the melting/freezing times of PASA with those of the PA-SA/EG composite PCM
Summary
Phase-change materials can store or release thermal energy during phase transition [1]. Hassan Nazir et al [14] prepared the multiple fatty acid and determined the eutectic point of each eutectic solution according to the Schrader equation along with its thermophysical properties These eutectic PCMs have a phase-transition temperatures range of 27–75°C and latent heat of 127–210 kJ/g, which are suitable for solar water heating, building energy saving systems, and photovoltaic solar heating applications. Kadir Tuncbilek et al [15] prepared a eutectic solution of 69.0 wt.% lauric acid and 31.0 wt.% palmitic acid with a melting temperature of 35.2°C and latent heat of 166.3 J/g Their results indicated that the LA-PA eutectic mixture is a promising storage material at low-temperature energy with nice heat performance
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