Simulation Study On Thermal Performance Of Unitary And Zonal Phase Change Energy Storage Radiant Air Conditioning

Facing the contradiction between people’s growing need for a better life and unbalanced energy development policies,and the contradiction between energy shortage,strict environmental emissions and rapid global economic development,developing energy storage industry has broad prospects.Phase change materials are widely used in aerospace,building heating,communication power and refrigeration equipment because of their large latent heat value and many other advantages.With the approaching of the goal of "double carbon",the form of building energy saving is urgent and has great potential.In recent years,phase change energy storage technology has been gradually applied in building energy saving because it can alleviate the mismatch between energy supply and demand in time,space and intensity.Among them,the radiant air conditioning system combining phase change energy storage materials with capillary network has become one of the main technical means of building energy saving,which has brought remarkable results for building energy saving.In addition,the latent heat energy storage technology of sleeve(LHTES)is the most common technology in latent heat energy storage at present.Its principle is that the hot fluid(HTF)in the inner tube transfers heat from the fluid to phase change material(PCM)through the fins connected with the inner tube,and then PCM absorbs the heat and melts it,so that the heat in HTF is stored in the latent heat in the PCM in the sleeve,and then the heat is released in the lowtemperature fluid for utilization.At the same time,sleeve latent heat energy storage technology can be coupled with building radiant air conditioning to realize multiple energy storage.If the source term is simplified as HTF,then the design of fins will also provide a solution for latent heat system.The design of this thesis will focus on the key technical component units in the phase change energy storage radiant air conditioning system,create the key energy storage technology,establish the energy storage units of the latent heat system according to different functions,and finally superimpose different heat storage units according to the heat storage.Firstly,the vertical sleeve latent heat system with copying snowflake fin is used as the phase change heat storage water tank unit in the radiation air conditioning system,and the influence of the fin shape,length,thickness,angle,material and HTF temperature of the vertical latent heat system on the thermal performance of LHTES is emphatically analyzed by Fluent simulation,and the optimal vertical trapezoidal latent heat structure with 1/7 upper and lower bottoms is optimized.Then,the horizontal latent heat system of irregular copying snowflake fin is used as the horizontal pipe unit in the radiation air conditioning system for secondary heat storage.The shape,angle and distribution structure of irregular snowflake fin are optimized by natural convection generated during PCM melting.Finally,the fin size angle with the optimal solution value is optimized by using response surface method combining the two objectives of shortest melting time and maximum heat storage.Finally,the air conditioning terminal device is designed as a combination of single-layer radiant cool storage ceiling and double-layer radiant energy storage floor for indoor comprehensive thermal management,and the stability analysis of the internal temperature of the building under the disturbance of outdoor heat flux is analyzed,and the corresponding response characteristics are obtained.Through the research of this thesis,the movement process of phase change materials during melting will be obtained,and the key influencing factors of strengthening heat transfer will be revealed.A new optimization process of latent heat system of bushing will be proposed,and the optimal fin structure in latent heat system including phase change materials will be optimized.A set of optimal optimization schemes for radiation air conditioning systems will be proposed,and energy storage units in different functional areas will be built,which will lay a technical application foundation for promoting independent innovation of thermal management of phase change energy storage technology.