THB Advance/Basic – Phase change material – Thermal conductivity
A phase change material (PCM), which is also referred to as latent heat storage (LHS) material, changes its state of matter at certain a phase change temperature from typically solid to liquid and vice versa. During the melting or solidification, the material can store or release large amounts of energy, thus, it can be used for cooling or heating applications. The most common applications are cold packs and heat pads. Other examples are catering industry, building industry, automotive or clothing. Well-known PCMs are water or sodium acetate, the latter is e.g. used in the above-mentioned heating pads.
The below shown example shows the analysis of the thermal conductivity of two hydrated salts. At room temperature both PCMs were liquid.
The liquids were filled into a beaker, which was placed in a tempered liquid bath. For the measurement the sensor THB/B/Metal was hung into the sample. The measured temperature steps were -20 °C, -10 °C, 0 °C, +10 °C, 20 °C (room temp.) and +30 °C, thus the measurement was started in the solid state of the material. Three measurement points were recorded at each temperature level and averaged.
The thermal conductivity of Sample A slightly increases with heating up to 0 °C, whereas Sample B shows slightly decreasing values. Both samples change from the solid to the liquid state in the temperature range from 0 °C to 10 °C which can also be clearly seen in the thermal conductivity drop. With increasing temperature, the thermal conductivity of both samples increases slightly. In general, Sample B shows higher thermal conductivities compared to Sample A.