Palmitic Acid-Lauric Acid/ Expanded Graphite as Form-Stable Composite Phase Change Material for Low-Temperature Energy Storage Applications

TB35; Low thermal conductivity of binary fatty acid mixture of palmitic and lauric acids ( PA-LA ) within the value range of 0. 15-0. 17 W/( m · K) restricts its wide utilization as thermal energy storage material in the active regime of solar heating applications at low operating temperatures. Nevertheless, this mixture as phase change material ( PCM) has a suitable phase-change temperature and heat of 36 ℃ and 176.3 J/g, respectively. Hence, the objective of this study is to formulate a novel form-stable composite PCM with the PA-LA mixture and expanded graphite ( EG) as a thermal enhancer. PA-LA eutectic mixture with varied concentrations of EG was prepared and characterized. The thermal conductivity of PA-LA/EG increased gradually with the mass of EG. Optimum thermal properties were observed in PA-LA/( 5％ EG) composite, where its melting ( Tm ) , freezing temperature ( Tf ) , latent melting heat and thermal conductivity was 35.53 ℃,34.84 ℃, 174 J/g, and 1.19 W/(m·K), respectively. Also, the composite PCM is characterized by good chemical-thermal stability and thermal reliability for long-term usage. In conclusion, it can be utilized as a prospective form-stable PCM for thermal energy storage in solar heating systems, overheat treatment systems, and other thermal storage applications at low operating temperatures.