THE INFLUENCE OF THE PHASE CHANGE TEMPERATURE RANGE AND THE PHASE CHANGE HYSTERESIS OF A PCM ON THE PERFORMANCE OF AN AIR-PCM HEAT STORAGE UNIT

The influence of the phase change temperature range and the hysteresis of the enthalpy-temperature relationship h(T) of PCMs on the performance of thermal energy storage (TES) systems is rarely quantified. In the present study, the quantification is done by the comparison of the amounts of heat stored in (and discharged from) the air-PCM heat exchanger (TES unit) operating between constant air temperatures. All simulations were conducted for the same mean phase change temperature of the PCM (30 degrees C). The inlet air temperature of the air-PCM HEX was 40 degrees C during the heat charging period and 20 degrees C during the heat discharge period. The maximum considered phase change temperature range of the PCM was 10 degrees C. The maximum phase transition hysteresis, in the study defined as the temperature difference between the melting and solidification peaks, was 4 degrees C. The results indicate that in case of the PCMs with a wide phase change temperature range and a significant hysteresis of the h(T) curves, the influence of these properties cannot be neglected in the simulation studies in order to achieve accurate results.