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 to 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 multiphase flow area.
The results show that the melting process of paraffin can be divided into
four zones: liquid zone, multiphase flow zone, porous media zone and solid
phase zone. According to the polarizing optical microscopy (POM) picture,
the continuous phase and discrete phase transition relationship between
solid wax crystal and liquid paraffin is captured. The POM picture is
statistically analyzed, and the critical liquid phase ratio of the
transition from porous media area to multiphase flow area is given under
experimental conditions.
Division of paraffin melting zone based on multiscale experiments
