Detail:This Lesson includes the basic thermophysical relations and approaches for simplified one–dimensional mathematical description processes of heat transfer and phase changes. The lesson is designed to teach the necessary skills for thermal behaviour modelling of composite materials (including PCM components) using a special tool, which is developed for numerical calculations. Possibilities and limitations of one-dimensional transient approaches with semi-infinite and limited thickness of material layer in different outer heat exchange conditions are characterised. Structure and user dialog details of the tool used for calculations are demonstrated. Examples of time dependent thermal processes related to numerical solution of Stefan problem are demonstrated. It is also possible to compare results of these calculations with numerical solutions of corresponding problem in WUFI Plus program environment.