Experimental study on the thermal stability of a paraffin mixture with up to 10,000 thermal cycles

Thermal energy storage (TES) technologies utilizing phase change materials (PCMs) have been extensively investigated and developed in the last three decades. A great deal of previous research into PCMs has focused on their reliability and stability after a number of repetitive thermal cycles. However, due to the heavy workload during the cyclic melting and solidification processes of PCM, the number of thermal cycles was normally no more than 1500, especially in the study of classic PCMs. In this research, an efficient and stable accelerated thermal cycling test-bed, which could interchange the positions of PCM between a heat source and a heat sink automatically and periodically, was designed, constructed and tested. In addition, properties (melting point and heat of fusion) of a commercial grade paraffin mixture were investigated with up to 10,000 thermal cycles. The experimental results presented that the degeneration of the heat of fusion was 9.1% after 10,000 thermal cycles while that of the melting point was negligible. Therefore, it would be a very promising PCM used in the latent TES system which required absorbing and releasing energy frequently. Moreover, the experiment demonstrated that the developed accelerated thermal cycling test-bed worked well.