This master thesis investigates the delay of the melting process (difference between the temperatures TStart and TOn) for phase change materials (PCM) that is observed in differential scanning calorimetry (DSD). The goal of this thesis is to analyse the delay in more detail and reveal the effect of thermal conduction on the shift of the melting point. Knowledge about the temperature range of phase transitions is of great importance for the performance of latent heat thermal energy storages (LHTES). To shed more light onto this matter, the DSC process is analysed in detail to develop a model for numerical simulations. In the end the DSC process is reduced to a one dimensional heat conduction problem. In the beginning of this thesis, the basics of thermodynamics and the differential scanning calorimetry process is discussed, followed by an introduction to the aforementioned model and explaining the used numerical method. Afterwards, the model is tested and verified with a well-known standard, namely sapphire. Finally, the simulation was carried out for the PCM, which resulted in the finding, that thermal conduction was accountable for the delay extent decreasing with the heating rate. The existence of the delay itself is due to a different reason, which will be discussed in the theoretical section of the thesis.