Enthalpy of Phase Change Materials as a Function of Temperature: Required Accuracy and Suitable Measurement Methods

Phase change materials (PCMs) are thermal storage materials with a high storage density for small temperature range applications. In the design of latent heat storage systems, the enthalpy change of the PCM has to be known as a function of temperature with high precision. During dynamic measurements, the sample is not in thermal equilibrium, and therefore the measured value is not the equilibrium value. The influence of non-equilibrium on the measurement results can be quantified by doing measurements during heating and cooling with any measurement instrument. Measurements carried out by differential scanning calorimetry (DSC) and by the T-history method are presented and discussed. To characterize encapsulated PCM objects, measurements on the whole objects should be carried out. A measurement setup for this purpose is also presented. The obtained precision meets typical application requirements, and good agreement between results obtained with the different methods is demonstrated.