Experimental And Simulative Study On The Heat Storing Performance Of The Solar Energy Storage With Phase Change Material

As a renewable clean energy,the solar energy has a broad application prospects in the current tight supply and increasing demand. But unfortunately,how to store the solar energy becomes a big obstacle in its development.Thermal storage provides us a valuable solution for correcting the mismatch that is often found between the supply and demand of energy.Latent heat thermal energy storage(LHTES) in a phase change material(PCM) is very attractive,because of its high-energy density,its easy control and its isothermal behavior during the phase change process.Internal and overseas,a great deal of research has been carried out on the nature of phase change materials and the process of thermal analysis,but researches for LHTES are still insufficient.In order to resolve this problem mentioned above,firstly the author selected the paraffin as PCM and tested its density,volume expansion during the melting,thermal conductivity,phase change temperature and the latent heat.And then setting up the testing device of shell-tubes phase change thermal storage and doing the experiments under normal temperature, temperature field changes with time is obtained and the temperature change law in different positions is significantly analyzed.From the result the author also analyzed the influence of the heat transfer fluid inlet temperature and the flow on paraffin's melting process.It is found that the heat transfer fluid inlet temperature for storage time is greater than the impact of its flow.Further,in the aspect of simulative study,the physical model was simplified to be a shell-tube unit with PCM being around and heat transfer fluid flowing inside.By using solidification/melting models of FLUENT software,the melting process of paraffin in a shell-tube is numerically simulated.Considering the nature convection in the liquid phase and the hot media coupled with the unit,temperature field is obtained and phase change interface position changing with time is still calculated.In this study,it is found that the results from the FLUENT are also contracted with the experimental results,which proves the FLUENT software is feasible to deal with the phase change problems.The thesis is then based on the simulation model to optimize the structure of heat transfer enhancement,comparing the melting times in the different structure parameters of the ring fin.According to the similarity theory,the experimental model is magnified as a real device which can apply to a kind of separated solar water heating system thus the original system can be improved.The conclusion of this thesis can offer instructions to the designers to reduce the repetitious work and enhance the performance of research. In addition,the numerical simulation method discussed in this thesis can be used in the design and research of the heat transfer enhancement, which partly replaces the experiments,largely saves the manpower and material resources...