Long-term thermal and chemical reliability study of different organic phase change materials for thermal energy storage applications

The purpose of this experimental study is to determine the thermal and chemical reliability of organic phase change materials (O-PCMs) viz. paraffin, palmitic acid, and myristic acid for 1500 accelerated melt/freeze. The differential scanning calorimeter (DSC) was used to measure the melting temperature and the latent heat of fusion at zeroth cycle and after 100th, 500th, 1000th, and 1500th thermal cycles. The DSC results show the gradual changes in the value of thermophysical properties of all the tested PCMs. The changes in melting temperature of paraffin, palmitic acid, and myristic acid have been found in the range of +0.72 to +3.27, -0.29 to +1.76, and -2.09 to +1.5 degrees C, respectively, and the latent heat of fusion in -9.8 to 14.2, 3.3 to 17.8, and 0.9 to 9.7 %, respectively. The Fourier transform and infrared spectroscopy (FT-IR) technique was used to investigate the changes in the compositional/functional group of the O-PCMs before and after thermal cycles. The FT-IR spectrum confirms the chemical stability during the thermal cycle test. The experimental results show that these organic PCMs possess a good thermal reliability in terms of melting temperature and the latent heat of fusion and chemical stability during thermal cycle testing.