Abstract: [Objective] In order to provide theoretical bases for the development and application of a new kind phase change energy storage floor used in ground with heating system, the thermal performance of phase change energy storage floor using fatty acid eutectic mixture as phase change material was investigated by a heat transfer mathematic model of ground with heating system in this study.[Method] Differential scanning calorimetry(DSC) and step cooling curves were used to analyze the thermal properties of eutectic mixtures of fatty acids. The chemical properties and thermal cycling stability was tested by DSC and Fourier transform infrared(FTIR). The applicability of fatty acid eutectic mixture to the ground of ground with heating system was confirmed, and the fatty acid eutectic mixture was selected as the phase change material for the phase change energy storage floor. The energy saving performance and heating effect of phase change energy storage floor was analyzed by a heat transfer mathematic model of electric ground with heating system. Firstly, the theoretical model of a typical room was chosen and the thermal dynamic process of ground with heating system was described. The operation of ground with heating system was set to a batch-type. Then, the heat transfer model of the room was established, the heat load was calculated, and the amount of phase change material and the heat transfer relationships between floor surface and indoor were confirmed. The heat transfer model of floor was lastly established, and the heat storage and release process of phase change energy storage floor was analyzed using ANSYS software. The changes of indoor temperature and floor surface temperature were observed, and the energy saving performance and heating effect of the electric floor heating system based on the phase change energy storage floor of fatty acid were analyzed.[Result] The phase change temperature of the fatty acid eutectic mixture was between 20-30℃, which satisfies the temperature requirements of the floor circumstance for floor heating system and thermal comfort of human body. The melting range of fatty acid eutectic mixture was only between 2 and 3℃, which will reduce the temperature change of room during the indoor heating process. The chemical properties of fatty acid eutectic mixtures were stable and after 1 500 cycles of freeze-melting cycle, the changes of melting point and latent heat were only 0.27℃ and 1.7%, respectively. The thermal stability of the fatty acid eutectic mixture was outstanding, which can meet the requirement of long-term application in floor heating system. The phase change energy storage floor used in floor heating system can move the electricity from the peak to the valley and make the temperature of indoor and floor surface within the proper range of human body.[Conclusion] The heating effect and energy saving performance of phase change energy storage floor used in floor heating system were proved to be superior. By changing the type and ratio of the fatty acid eutectic mixture, the phase change temperature could be adjusted flexibly so that the phase change energy storage floor of fatty acid would play a good energy saving and heating effect in different climate areas and different heat load buildings which has great potential for development.

Key words: floor used for ground with heating system, phase change energy storage, fatty acid, heat transfer model, ANSYS simulation