Phase change materials, useful in many areas, are important because of their ability to store and release heat over a small temperature interval. In the first part of the assignment, we theoretically discuss phase changes and properties of the phase-changing material paraffin wax. To observe the melting and solidification of phase-changing materials, we have designed a transparent chamber that can be used to observe solid-liquid phase transitions and measure the temperature field as a function of time. The experiment was carried out on an experimental device developed as part of this Bachelor thesis, which allows separate establishment of hot and cold circuits while measuring the flow, temperature and pressure of the working fluid (water). We installed five thermocouples in the transparent chamber
and measured temperature during melting and solidification as a function of time, boundary and initial conditions. We also measured the difference in volume between the liquid and solid phases of the paraffin wax. Initial and boundary temperatures were between 20 and 75 °C. The results show that the latent heat significantly influences the course of paraffin wax's solidification and melting process and that the volume of the solid phase of the selected phase-change material is about 15 % smaller than the liquid one. The long duration of the
experiments (from 2 to 6 h) indicates the need to install channels to increase the heat transfer surface, intending to accelerate phase transitions, which is essential for effective use.
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