Nowadays,due to the massive exploitation and use of fossil fuels,the problem of global warming is becoming more serious,making this energy model unable to continue indefinitely.Therefore,the application of renewable energy has been developed rapidly.Solar energy,a new energy,has entered the eyes of many researchers,but solar energy has strong intermittence and volatility,so it is difficult to use rationally.However,phase change heat storage technology can well balance the mismatch between thermal energy supply and demand.And the phase change heat storage technology has the characteristics of high heat storage density and approximate constant temperature of heat storage and release,which is of great significance to improve the utilization efficiency of renewable energy and reduce the cost.Among them,the phase change heat storage technology using a phase change capsule cascade packing bed for latent heat storage has stability and high thermal characteristics,so it is widely used.It is an excellent scheme for the storage and utilization of solar energy.First of all,a 3-stage disordered cascaded packing bed with variable diameter is established and simulated by ANSYS software,and the simulation results are compared with the corresponding data of the existing experimental platform to ensure the authenticity and reliability of the simulation results.In addition,three kinds of 3-stage equal-diameter disordered packing beds are established,and the capsule size of each kind of equal-diameter packing bed is the same as that of a variable-diameter packing bed.At the same time,different phase change materials(PCM)are filled in each stage of four kinds of packing bed,and numerical simulation is carried out.The effects of equal-diameter packing beds and variable-diameter packing beds on thermal performance are discussed and compared,respectively.The results show that in the equal diameter packed bed,the smaller the diameter of the capsule is,the shorter the heat storage time is,the better the dynamic temperature field uniformity(FITU)is,and the higher the energy storage efficiency is,but the greater the pressure drop is.On the other hand,each layer of the variable diameter packing bed has a similar thermal performance to the equal diameter packing bed of the same layer and capsule size,but it has obvious advantages over the equal diameter packing bed in heat storage and storage,which is 2.0% and 4.2% higher than the equal diameter packing bed under the optimal arrangement,respectively.This shows that although the 3-stage arrangement of the equal-diameter packed bed has obvious advantages compared with the same series,the variable-diameter packing bed layout is not the optimal layout.To further verify the superiority of a 3-stage variable diameter packing bed,three kinds of equal diameter packing bed and variable diameter packing bed are established,which have the same average capsule diameter and the same average melting point of PCM filled in the capsule,to verify the influence of series equal diameter packing bed and variable diameter packing bed.The effects of equal diameter packed bed and variable diameter packed bed on thermal performance under different arrangement stages are discussed and compared respectively.The results show that the phenomenon of non-simultaneous melting exists in both equal-diameter packing beds and variable-diameter packing beds,and the first melting part of an equal-diameter packing bed is the same as that of a variable-diameter packing bed.In terms of heat storage time,the single-stage packing bed is similar to the 2-stage equal-diameter packing bed,and the 2-stage variable diameter packing bed and the 3-stage variable diameter packing bed are also similar.The temperature field uniformity(FTU)of the four kinds of packing beds is almost the same in the early stage of heat storage and almost the same in the later stage of heat storage.In addition,the3-stage variable diameter packed bed has obvious advantages in heat storage and storage.This shows that compared with the single-stage and 2-stage packing bed,the 3-stage variable diameter packing bed has obvious advantages,but it needs to be properly optimized.In this paper,the phase change capsule cascade packing bed with different stages and different types of arrangement is numerically simulated and calculated.The simulation results provide a reference basis for the application of phase change capsule cascade packing bed in real life and the optimization of heat storage performance of phase change capsule packing bed. |