Study On Heat Transfer Performance Of Phase Change Storage Electric Heating Module

In recent years,electric heating,as a form of clean energy heating,has been popularized and applied.According to the preferential policies of electricity consumption in different regions,the system form combining electric heating with phase change heat storage has become a research and application hotspot,aiming at realizing peak shifting and valley filling of heating electricity so as to reduce the overall heating cost.However,the commonly used inorganic phase change materials still have problems such as poor thermal conductivity,high degree of undercooling and easy leakage,and the overall heat transfer efficiency of the phase change storage electric heating system is low.All these problems are important factors that hinder the further promotion of this heating form.In this paper,a phase change storage electric heating module is designed and studied.Specifically,Ca Cl₂·6H₂O is used as phase change material and Sr Cl₂·6H₂O is added to reduce the supercooling degree of phase change material.Expansive graphite（EG）was selected as the carrier of porous media,and its microporous structure was used to adsorb phase-change materials（PCM）to prepare composite formalized PCM.In order to improve the overall thermal conductivity and forming effect,the expanded graphite（EG）was packaged into a module with carbon fiber electric heating wire,and the combination between heat source and PCM was improved.The module can be used for radiant floor heating of rooms,and can be freely spliced according to the requirements of room heating to meet the heating requirements of existing buildings and new houses.The thermal and physical properties of the material and the heat storage and release characteristics of the module are studied by means of experiment and simulation.In terms of experimental research,two works are completed.One is to design the preparation experiment of composite shaped phase change materials by using orthogonal experimental design method.By testing the composite shaped phase change materials with different ratio of raw materials,the factors such as the degree of undercooling,forming effect,heat storage density and thermal conductivity are comprehensively considered.It was found that 88%Ca Cl₂·6H₂O+2%Sr Cl₂·6H₂O+88%10%EG（50 mesh,100 mesh）was the best raw material ratio,and the ratio was applied to the production of phase change storage electric heating module.Second,carbon fiber electric heating wire,composite shaped phase change material and aluminum alloy shell were used to make the phase change electric heating module,and the heat storage and release performance was tested.It was found that the phase change material could attenuate and delay the temperature change of the electric heating wire,and the heat storage time could be shortened by increasing the heating power of the module.In the same environment,the change of electric heating power has little effect on the heat release process.In the aspect of simulation research,the enthalpy method model was used to establish a simplified mathematical model for the phase change heat storage electric heating module,and the Fluent software was used to solve and analyze the model.By comparing with the experimental data,the reliability of the model was verified,and the heat storage and release characteristics of the module were preliminarily analyzed.Finally,the effects of thermal conductivity,electric heating power and wire spacing on the heat storage and release performance of the module were studied by using the established model.It was found that the good thermal conductivity of PCM could make the heat transfer in the module efficient,and ensure the uniform change of internal temperature field and the continuous release of surface heat.High electric heating power will lead to obvious overheating of the temperature of the module,reducing indoor comfort,but too low also means that the heat storage rate of the module will decrease,and the effective heat release can not be sustained;When the electric heating power is9.85W/m and the thermal conductivity is 4W/（m·K）,the wiring spacing of the carbon fiber electric heating wire should be between 40mm and 45mm,which can ensure the high heat storage efficiency and heating continuity of the module,complete the optimization of the phase change electric heating module and provide parameterized suggestions for future design and application.