Mathematical model of heat transfers during phase transition of heat storage material

Abstract

The use of paraffin as heat accumulators in building envelopes is difficult due to the rather high temperature of their phase transition, and low coefficient of thermal conductivity. Besides, traditional insulation systems using heat-insulating material in energy-active structures are ineffective. To improve the energy efficiency of residential buildings, it becomes necessary to develop new systems and structures of fencing, which is active in nature and can use renewable energy sources for the needs of buildings. It will also reimburse part of the heat spent on heating the building. For this, it is necessary to study the heat exchange processes in the building structures.
Тhe article presents the results of studying the processes of phase transition of heat storage material in enclosing structures. The article considers processes of phase transition of heat storage material in enclosing structures, considering the prerequisites and assumptions. They are necessary to simplify the mathematical model of the phase transition process. The authors have been developed a mathematical model of heat transfer during the phase transition of a heat storage material, which considers the thermophysical properties of the material, the thickness of the phase transition layer and the time of its formation, as well as the temperature difference between the temperature of the initial state and the temperature of the phase transition of the heat storage material. It was found that the heat flux density varies in many parameters from the initial moment of time to the time of the process of transition to a new phase and it is determined that the average heat flux density during the melting of a layer of heat-accumulating material is two times higher than the heat flux density at the moment of time, at which the phase boundary will move a distance.