Study On Preparation Of Composite Phase Phange Material For Air-conditioning And Cool Storage Tank Characteristics Of Charging And Discharging Process

With the increase of China's overall national strength and the improvement of people's living standards,the rapid increase in the use of centralized air-conditioning systems in China has led to a more severe power consumption problem.At the same time,the peak-to-valley difference of the power system has increased drastically,and the power grid load rate has dropped significantly.This has greatly affected the cost of power generation and the safe operation of the power grid.Therefore,the centralized air-conditioning system has become one of the key areas for energy conservation and emission reduction.Therefore,the application of cold storage technology in the field of central air conditioning is one of the effective measures to solve the problem of peak urban electricity consumption,excessive valleys,and mitigation of large amounts of energy consumption.It plays an important role in the "peak load shifting"of electricity systems.Today's widely used cold storage air-conditioning system is the ice storage air-conditioning system,but the freezing point of water is low,which makes the refrigeration unit evaporation temperature and COP is lower,and increases the complexity of the system.Therefore,it is necessary to develop a phase change material that can be used in an air-conditioning cold storage system and has a freezing point higher than ice.In general,a single phase change material(PCM)is used for charging in the air-conditioning cold storage device.However,the PCM has a low latent heat and a low thermal conductivity,which makes the charging capacity and charging rate of the accumulator are low.To overcome this problem,air-conditioning using muti-PCM air-conditioning cold storage system has been proposed.This method can widen the range of temperature for matching the air conditioning conditions with the phase change material,and to construct a multi-PCM cold storge tank.The heat transfer characteristics of the charging and discharging progess are studied.The main research work and research results are as follows:(1)A novel inorganic phase change cold storage material HNS-6 was prepared,which used for a muti-PCM cold storge tank.To solve the problem of large degree of supercooling,it is proposed to add nucleating agents and nanoparticles to reduce the degree of supercooling,and eventually developed a novel of inorganic nano-PCM.The physical parameters of HNS-7were measured by cooling curve method and differential scanning calorimetry(DSC).The physical parameters include phase change temperature,phase change latent heat,specific heat.(2)Established the 3D physical model and mathematical model of the muti-PCM cold storge tank,and carried out grid division and grid independt verification for the interior of the cold storge tank.A small-scale cold storage experimental device was set up,and the charging process of the cold storge tank was experimentally studied.Comparing the simulation values with the experimental values to verify the accuracy of the model;(3)The experimentally prepared HNS-7 and the selected PCM-2,PCM-3 are applied to a muti-PCM cold storge tank,when the volume ratio of HNS-7,PCM-2,PCM-3 is different,the charging and discharging characteristics of cold storge tank were studied.This paper was analyzed the change of the charging capacity,the charging rate,and the completion time of charging during the charging process of the muti-PCM cold storage tank.Beside,the paper also analyzed the change of the outlet temperature of the cold storage tank during the discharging process.Finally,the best combination ratio of the combined PCM(HNS-7:PCM-2:CM-3)is 5:2:1.(4)The cold storage tank heat transfer characteristics of charging and discharging process with a combined PCM ratio of 5:2:1 was studied.When the HTF inlet flow and HTF inlet temperature are different,the effects of liquid fraction,charging capacity,and temperature distribution in charging process of the muti-PCM cold storge tank and the influence on the outlet temperature of the muti-PCM cold storge tank during discharging process are studied.The phase change law of PCM in the cold storge tank is summarized.The theory and reference are provided for the optimization of the cold storge tank.