Optimization Of The Temperature Field Of Phase Change Storage Cold Storage

Cold storage,as an important part of the cold chain,is also a major energy consumer.In nowadays background of energy saving and emission reduction,the application of cold storage technology to cold storage,using phase change materials to store the cold energy during the valley power period,and the release of cold energy to meet the cooling requirements during peak power period,can not only bring great economic benefits to enterprises but also cut the peaks and fill the valleys of the power,effectively solve the contradiction of uneven power supply and the safety of grid system operation is also improved.In this paper,we designed and built a phase change storage cold storage experimental bench,and carried out relevant simulation studies and experimental research.The small-scale cold storage experiment is used for the verification and measurement of the physical property parameters of the cold storage material.On this basis,the parameters affecting the internal airflow organization of large cold storage cold rooms are investigated.The following conclusions were obtained.(1)In this study,suitable phase change cold storage materials were configured according to the literature,and cold storage materials encapsulated in cold storage plates were used.The cold storage plates were placed on top of the cold storage and it was found that the overall temperature rise time in the cold storage with the cold storage plates was extended by about 2 hours compared to the one without the cold storage plate.This indicates that the application of phase-change storage materials can delay the start-up time of refrigeration units and alleviate the dependence of the refrigeration industry on the grid,thus reducing the load on the grid.The process of temperature field variation in the cold storage with PCM plates was numerically simulated using CFD software,and the simulation results were consistent with the experimental results of the cold storage.It is shown that it is feasible to analyze the temperature field of the actual cold storage using numerical simulation,and provides a reference for the subsequent in-depth study of cold storage.(2)The temperature field of the small and medium cold storage sized cold storage plates was simulated,and the three-dimensional model of the small and medium-sized cold storage was established using CFD to study the effect of different placement and thickness of the storage plate on the temperature field inside the cold storage.When the cold storage plates were placed on top,the temperature of the cold storage was stratified on the top and bottom,and the temperature was relatively uniform on the same horizontal surface,but the temperature inside the storage and the surface temperature of the goods was lower compared with the other two arrangements.Using different thicknesses of cold storage plate on the top of the cold storage with the constant amount of cold storage materials,it was found that the temperature inside the storage decreases as the thickness decreases,which may be because the heat exchange area of the cold storage plate increases and the heat exchange was more adequate.Based on the study,the following recommendations were made: when placing the cold storage panels in the cold storage warehouse,priority should be given to using top-mounted cold storage panels,followed by using smaller thicknesses of cold storage panels as much as possible to increase the heat transfer area and extend the cold storage time of the panels for better storage of goods,if space allows.(3)Numerical simulations were conducted to compare the effects of different heights of cargo and different stacking methods on the temperature field inside the cold storage with cold storage plates,and the temperature inhomogeneity coefficient was introduced to evaluate the temperature field inside the storage cold storage.After 16 h of simulation,it was found that the overall temperature increase in the storage room was small under the condition of cold release from the storage panels,and the storage requirements could still be met.The surface temperature of the cargo was higher on the top layer and lower on the bottom layer.Goods with a height of 4.9 m had a smaller temperature increase compared to that of 2.8 m.From the temperature inhomogeneity coefficient,it can be seen that the minimum coefficient of the two-stack pressed seam stacked cold storage was0.94.Therefore,it is suggested that the two-stack pressed seam can be used for the stacking of cold storage goods similar to this paper to maximize the use of the storage space and store the goods with maximum efficiency.(4)The effect of different parameters of the air curtain on the efficiency of the air curtain was studied in the cold storage in the operation of the air curtain with the door open,that is,whether the air curtain can effectively isolate the damage to the fluid inside the cold storage by the hot air outside the storage.Analysis of the air curtain nozzle width,jet velocity,and jet temperature,the conclusions are as follows: with the increase in the width of the nozzle,the decay rate of the jet increases,and the air curtain isolates the hot air invasion efficiency decreased.Different nozzle widths had different optimal jet velocities,in the case of the nozzle width of 0.04 m,the jet velocity of 7 m / s,the jet in the library formed an obvious reflux,it can be considered that at this time the library of the lowest degree of damage to the flow field,only damage between the goods and the door.The jet velocity decreased with the direction of the jet,the amount of penetration at the door increased,and the temperature inside the depot was affected.As the jet temperature decreased,the area of influence on the library decreases,and the temperature inside the library showed a trend of temperature reduction.When the jet temperature was25 ℃,the temperature near the vault door was around 3 ℃,around-1 ℃ at 0 ℃,and around-5 ℃ at-18 ℃.From this,we can appropriately reduce the temperature of the air curtain jet to achieve the effect of maintaining a stable temperature inside the warehouse when the door is opened.