Study On The Performance Of Phase Change Heat Storage Electric Heating System

On the one hand,the northern winter heating energy consumption accounts for a considerable proportion,and the clean heating of isolated buildings such as rural houses needs to be adapted to local conditions,reasonable and effective solutions;On the other hand,the increasing contradiction between supply and demand in power peak valleys makes the phenomena of “shutdown” “abandoning wind” and “abandoning light” occur frequently,which seriously affects the healthy development of power industry.Air source heat pump under low temperature conditions is not economical,low temperature floor radiant heating comfort,heat storage,controllable,convenient and other characteristics,as well as the peak and valley price policy and relatively mature solar photovoltaic,wind power and other technologies,so that the regenerative electric heating technology is expected to become the most effective solution for clean heating of isolated buildings and peak load shifting.Based on the power supply operation mode under the policy conditions of photo electricity,wind power and peak-valley electricity price,electric ground heating should have the characteristics of large heat storage and rapid heat storage and release,and should be economically feasible.Therefore,this paper proposes a phase change heat storage electric heating system,and analyzes its material,structure,heat storage and release characteristics by theoretical analysis,experiment and numerical method,and obtains relevant conclusions.Details are as follows.First of all,through theoretical analysis,the system type,material composition and research scheme of low-temperature radiant floor heating with large heat storage and rapid heat storage are determined,namely,the floor heating system is composed of metal heating cable,non-woven reflective film,extruded polystyrene insulation board,leguminous concrete and phase change material.Paraffin is used as the main phase change material and expanded graphite is used as the porous medium carrier to enhance heat transfer and encapsulate paraffin,so as to effectively prevent paraffin melting leakage.Secondly,three paraffin / expanded graphite composite phase change heat storage materials with different proportions were prepared by porous physical adsorption method,and their parameters and heat storage and release characteristics were characterized by experimental test methods.Then,the heat storage and release characteristics of the composite phase change material layer test block system under different working conditions were prepared and experimentally tested.The results show that the heat storage and release performance of the composite phase change material layer electric heating system is significantly better than that of the ordinary soybean stone concrete layer electric heating system under the condition of power supply heating for 7h and power outage heating for 6h.The heating rate and heat storage effect of the test block system are improved with the proportion of expanded graphite in the composite phase change material.Finally,based on the characterization of composite phase change materials and test blocks and the experimental data of thermal physical parameters,the reasonable and effective numerical model and method of the electric heating test block system are determined.With the help of ANSYS FLUENT software,the heat storage and release characteristics of the electric heating test block system with different proportions of composite phase change materials,different thicknesses of heat storage layer,different heating cable spacing and different surface decoration layers are numerically studied.The results show that : 1)The latent heat of paraffin phase change has a great influence on the heat storage capacity of electric ground heating,and the amount of expanded graphite determines the heat storage and release rate of composite phase change material layer.2)The increase of floor thickness and the decrease of heating cable spacing will enhance the heat storage capacity.3)From the perspective of thermal comfort,the effect of wood flooring is the best,the temperature change is stable,and the surface is “uniform heat”.The research and results of this paper can provide a theoretical basis for the effective solution of the problems such as clean energy of isolated buildings and peak load shifting of electricity.