The effect of metal wool on the charging and discharging rate of the phase transition thermal storage material

Abstract

Thermal energy storage (TES) plays an important role in solar heat power systems. The use of phase change materials (PCM) and selecting additives to increase the rate of heat accumulation is a promising way to increase the efficiency and reliability of such systems.\nThe objects of the study were pure paraffin wax (PW) and composite PCMs based on it (containing aluminum and copper wool of 30 and 45\xa0μm in diameter, respectively).\nAn experimental setup with a cylindrical measuring cell was created, which was also considered as a model of a capsule with a thermal storage material. The rate of temperature change in the pure PW sample and samples of composite PCMs was experimentally measured. Two modes of heating and cooling were investigated: from 48 to 59\xa0°C (mode with a phase change) and from 30 to 40\xa0°C (mode without phase changes).\nHeating time from 48 to 59\xa0°C for the PW sample was 13\xa0min., for the PW samples with the content of aluminum wool of 0.00588 and 0.01780\xa0m3·m-3 − 11 and 10.5\xa0min., for the PW samples with the content of copper wool of 0.00524 and 0.01380\xa0m3·m-3 − 11 and 8\xa0min., correspondingly. The\xa0minimum heating time from 30 to 40\xa0°C was 6\xa0min. for the sample of PW with 0.01380\xa0m3·m-3 of copper wool in comparison with 9\xa0min. for the sample of pure PW.\nThe expediency of using copper wool as an additive to thermal storage materials of PW to increase the charging and discharging rate of TES devices without significantly raising their price was confirmed. The presence of metal wool in molten PW suppresses bottom-up convective currents, so the main mechanism of heat transfer is thermal conductivity. This fact will contribute to a faster equalization of the temperature field by the height of heat storage capsules