| China is the fastest growing country in using clean energy in the world.But in the process of development and utilization,for intermittency and timeliness of solar energy and wind energy,the imbalance of electricity consumption day and night both exist,the contradiction of peak regulation in power grid is increasing day by day,and the policy of the peak and valley electricity cost has been fully implemented in China.Energy storage has become the main technical way to utilize renewable energy and shift peak and fill valley on the power demand side of power grid and it is also the hot topic of relevant experts.As a thermal energy storage techinique,phase change energy storage has the advantage of good thermal energy storage performance.In this-paper,a microcapsule thermal storage unit of phase change material is designed,and the research on the heat storage and release characteristics of the phase change material is carried out through numerical simulation.In this paper,the physical model of heat storage unit with equal spacing of phase change microcapsules is established.The research on the effects of phase change material,wall material of microcapsule,mass content of phase change material in a single microcapsule and plate spacing of phase change microcapsule on the heat storage and release process of phase change material in microcapsules is performed through numerical simulation with Fluent CFD software.The variation law of volume fraction and average temperature of phase change material in microcapsule with time is analyzed.The results suggest that:1.when the initial temperature of the phase change material in the microcapsule is 324.15K and the inlet temperature of the heat transfer fluid is 343K,by comparing the liquid volume fraction of paraffin,stearic acid and palmitic acid in the process of phase change and calculating the phase change heat storage capacity,it is concluded that when the phase change material is stearic acid,the phase change heat storage capacity of phase change material reaches the maximum,the phase change heat storage rate of pure paraffin and palmitic acid is swifter,but the heat storage capacity of phase change is smaller;when the initial temperature of the phase change material in the microcapsule is 330.15K and the inlet temperature of the heat transfer fluid is 290K,through the comparison of the liquid volume fraction of paraffin,stearic acid and lauric acid in the process of phase change and the calculation of the amount of heat release,it can be concluded that when the phase change material in the microcapsule is stearic acid,the phase change heat release rate is slower,and the amount of heat release is larger;2.When the phase change material is pure paraffin and its initial temperature is 324.15K,by comparing the liquid phase volume fraction and calculating the heat storage capacity of the phase change material in a single microcapsule when the mass content of the phase change material in a single microcapsule is 14.58%,15.06%and 17.07%respectively,the results suggest that when the mass content of the phase change material in a single microcapsule is 17.07%,the phase change heat storage of the phase change material is the largest.When the mass content of the phase change material in a single microcapsule is 14.58%and 15.06%,the heat storage rate of phase change is faster,but the heat storage capacity is smaller;when the phase change material is pure paraffin and its initial temperature is 330.15K,through the comparison of the liquid volume fraction in the process of phase change and the calculation of heat release capacity when the mass content of the phase change material in a single microcapsule is 14.58%,14.84%and 15.06%,what is concluded is that when the mass content of the phase change material in a single microcapsule is 15.06%,the heat release capacity of the phase change material is larger,and the heat release rate of the phase change material is higher,but the heat release capacity is smaller when the mass content of the phase change material in a single microcapsule is 14.58%and 14.84%.3.When the phase change material is pure paraffin and its initial temperature is 324.15K,through the comparison of the liquid volume fraction in the process of phase change and the calculation of phase change heat storage capacity when the wall material of microcapsules is urea formaldehyde resin,polystyrene,polyving akohol and polythene respectively,it is concluded that when the wall material of microcapsules is urea formaldehyde resin,the heat storage capacity of phase change material is larger and the heat storage rate of phase change is faster;when the phase change material is pure paraffin and its initial temperature is 330.15K,through the comparison of liquid volume fraction and the calculation of heat release capacity of phase change when the wall material of microcapsules is urea formaldehyde resin and polystyrene,it is concluded that when the wall material of microcapsules is urea formaldehyde resin,the heat release capacity of phase change is larger,and the heat release rate of phase change is faster,thus it is determined that the urea formaldehyde resin is the wall material of microcapsules.4.When the phase change material is pure paraffin,by comparing the liquid volume fraction of the phase change material and calculating the heat storage and heat dissipation capacity of phase change when the plate spacing is 40mm,30mm,20mm,it can be known that when the spacing between microcapsule plates is 20mm,the phase change heat storage and heat release rate is faster,and the heat storage capacity and heat dissipation capacity of phase change is larger,thus it is determined that the spacing between microcapsule plates is 20mm. |
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