Study on the influence of rating charge on temperature and phase behavior of stabilized matrix wax-based thermal storage

Abstract

The rating charge characteristic is crucial for the heat energy storage, particularly for lowtemperature system which uses paraffin wax. The influence of different rating charge causes severe temperature fluctuation, which is undesirable for the heat system. It is affected by unstable phase transformation, reducing the heat distribution and makes the average rating charge insufficient. In this work, the fluctuation can be minimized by adding polyethylene plastic as phase stabilizer for the wax. The polyethylene is added by ratio of weight of 15% from the total mass of 134 grams. Each material is mixed in the liquid state, stirred and molded into the apparatus. The phase transition evaluation is performed, showing the mixture indicates an additional transition peak after the principal phase transformation, ranging between 15.26 °C – 19.34 °C (melting) and 11.98 °C – 9.45 °C (freezing). The steady operation makes the lowest rating variation is only 0.3 °C/min, which is obtained by the mixture of wax and polyethylene. In the same rating charge, the wax has rating variation of 2.9 °C/min, signifying the effect of unsteady melting transition. It clearly demonstrates the addition of polyethylene for the mixture promotes a better phase transformation under various rating charge, maintaining the effective temperature distribution for the heat storage.