Preparation And Application Of Stearic Acid/Expended Graphite Composite Phase Change Heat Storage Materials

In this study stearic acid (SA) as phase change heat storage materials, expended graphite (EG) as the absorbed carriers, stearic acid/expended graphite composite phase change heat storage materials (PCM) for wood solar drying was prepared. Its microstructure and thermal physical properties were analyzed. The PCM was added into the conventional heat storage water tank to strengthen the capacity of heat storage/retrieval, and the effect of the addition of phase change thermal storage units on the performance of solar drying system was studied in this paper. The results were as follows:(1) The composite PCM was prepared with an optimum mass ratio of SA:EG= 9:1, SA can be be well encapsulated, and showing a good cycle thermal stability.The melting and freezing phase change temperatures and latent heats of the optimal PCM were 52.74 and 53.70℃ and 169.90 and 166.10kJ/kg, respectively.(2) The heat transfer efficiency of heat storage/retrieval and the nonuniformity of heat release can be improved with the addition of EG. The time required for heat storage/retrieval with the PCM decreased by 39.74% and 45.09%, respectively, compared to SA.(3) The addition of the phase change heat storage units has a significant effect on the heat release of the heat storage tank. The heat release rate reduced with the rise of temperature difference and increased with higher heat storage unit volume. When the heat storage unit volume in the heat storage water tank was 35%, The heat discharge time of latent heat storage water tank was 1.26 times more than that of conventional heat storage water tank, the heating temperature can be scarcely increased by 8.7℃, the heat efficiency can be increased by 22.56% at most.(4) Solar drying experiment was studied on the 40mm thickness cunninghamia lanceolata. Compared with the ordinary water storage tank system, the latent heat storage tank system for wood drying, when solar radiation intensity was insufficient, the temperature of the phase change thermal storage chamber was significantly higher than that of the ordinary water tank, the temperature of the drying room varied slightly, the drying rate increased by 33.3%.