Design And Optimization Of The Cold Energy Storage System Based On Phase Change Materials

Cold storage is the technology to store low temperature energy temporarily under the ambient temperature for later use.It is the supplement and adjustment of refrigeration technology and an economical and feasible way to coordinate the mismatch between the supply and the demand of cold energy in time and intensity.Appling cold storage technology in the refrigerated warehouse;the cold energy is stored in the cold storage medium when the power load is low at night,and then the cold energy is released in the peak period of the power load to meet the demand of the peak cooling load at daytime.That can not only bring huge economic benefits for the enterprises,but also can cut the peak and fill the valley;solve the contradiction between power supply and demand effectively and improve the safety of power system operation.In this study,the phase change cold storage refrigerated warehouse was designed and built,and the relevant simulation research and experimental research were carried out.The arrangement,structural and running parameters of the ice-on-coil storage plate,which is the core device in the cold storage system,were optimized and analyzed.The main work and conclusions are as follows:(1)A feasible scheme and an operation strategy of the refrigerated warehouse integrated with the latent heat cold storage technology was presented.The refrigeration system provides cold energy to cold storage plates directly and the product in the refrigerated warehouse through an evaporator,respectively.And the product absorbs the cold energy released from the cold storage plates during the melting process at daytime,while the refrigeration system is off.Taking the 0-5 ℃ experimental refrigerated warehouse as an example,the payback period is two years and seven months.(2)An experimental refrigerated warehouse and data acquisition system were designed and built,based on which,the structural and running data were collected.The mathematical model of refrigerated warehouse was established and verified by the experimental temperature data.(3)The analytical model,physical model and mathematical model of phase change cold storage refrigerated warehouse were established,among which there was good consistency.Based on the parameters verified by the refrigerated warehouse model,the mathematical model of the phase change cold storage refrigerated warehouse was established.The simulation of the releasing process of the phase change cold storage refrigerated warehouse was carried out to verify that the phase change cold storage refrigerated warehouse could meet the requirements in practical application,and the simulation results showed good consistency with the experimental results.Besides,an economic analysis was carried out,showing a short payback period and excellent returns.(4)The arrangement,inlet temperature,inlet flowrate,coil density and coil diameter of the ice-on-coil storage plate were simulated and analyzed.The cold storage plates attached on the floor can make an effort to the air convective heat exchange at the lower part of the refrigerated warehouse;meanwhile,those installed on the sidewall can have a better control on the overall temperature distribution.A higher cold storage rate and capacity,and a shorter time required for ice storage process can be addressed by either reducing the inlet temperature or increasing the inlet flowrate,but the effect of the former is much better than the latter.Raising the coil density or diameter can promote the cold storage process and shorten the ice storage time,as well as increase the cold storage rate and capacity.The effect of raising the coil density is better in shortening the ice storage time,but with the increase of the coil density,the effect is attenuated.However,the effect of raising the coil diameter is better in improving the storage rate and capacity,and with the increase of the coil diameter,the effect shows a strengthening trend.