Division of paraffin melting zone based on multiscale experiments

Abstract

Phase change energy storage materials are widely used in the field of renewable energy. Paraffin is one of the common phase change energy storage materials. As a multi-component hydrocarbon mixture, the melting of paraffin is different from that of pure substance. In addition the solid and liquid zones, there is also a fuzzy zone in which solid and liquid coexist. In this paper, the melting characteristics of paraffin in phase transition zone are studied by multi-scale experiments. Through the visualization experiment of square cavity paraffin melting, the solid zone, fuzzy zone and liquid zone are determined, and the moving process of phase interface is tracked by digital pictures and infrared heat maps. The evolution process of the pore structure in the fuzzy zone under different temperatures is photographed by means of the micro-experiment, and it is revealed that there are two areas in the fuzzy zone, porous media area and multi-phase flow area. The results show that the melting process of paraffin can be divided into four zones: liquid zone, multi-phase flow zone, porous media zone, and solid phase zone. According to the polarizing optical microscopy picture, the continuous phase and discrete phase transition relationship between solid wax crystal and liquid paraffin is captured. The polarizing optical microscopy picture is statistically analyzed, and the critical liquid phase ratio of the transition from porous media area to multi-phase flow area is given under experimental conditions.