The Influence of Composition Ratio on the Thermal Performance Parameters of Eutectic Phase Change Materials: Experimental Research and Theoretical Prediction

Eutectic phase change material (EPCM), compared with single phase change material (PCM), is widely studied by many scholars due to its flexibility in practical engineering applications by the characteristic of changing phase change temperatures. However, there is still a lack of theoretical prediction research on the thermal performance parameters of EPCM. The existing theories about EPCM are unable to accurately predict its thermal performance parameters, which increases the difficulty of selecting the composition ratio of EPCM and affects its practical application. Based on a background of the accurate prediction of EPCM thermal parameters, 12 binary EPCMs, and 7 ternary EPCMs are prepared by mixing capric acid, n-octanoic acid and tetradecane with different proportions, respectively. By using the cooling curves and DSC test, the variation patterns in thermal performance parameters of EPCMs are studied. After comparing various thermodynamic models, the Schrader model was selected and combined with experimental results to compare and calculate the experimental and theoretical values of thermal performance parameters. The results show that the binary PCM reaches the minimum eutectic point of 1.42 °C at a mass ratio of 0.33:0.67 for capric acid to n-octanoic acid, while the ternary PCM reaches the minimum eutectic point of 0.34 °C at a mass ratio of 0.231:0.469:0.3 for capric acid, n-octanoic acid, and n-tetradecane. The latent heat of a EPCM is between the lowest and highest values of the latent heat of the constituent components, and its value increases with the enhancement of the overall thermal storage density of the material. The modified Schrader equations can effectively predict the phase change temperatures and latent heats of EPCMs at different composition ratios. The equation has a fitting accuracy of over 0.986 and a bias error of less than 6%, demonstrating excellent accuracy and providing a reliable theoretical basis for the proportion design and thermal parameter prediction of EPCM in actual engineering applications.