Heat Storage Characteristics Of Phase Change Materials And Phase Change Material

In today's society,the demand for resources and energy is increasing,while the reserves of traditional fossil energy are decreasing,and the dependence of society on traditional fossil energy does not reduce.In recent decades,although,new energy has made considerable progress,it still can not replace the status of traditional fossil energy.Therefore,energy conservation has become a top priority.How to make efficient use of existing energy has become a topic of common concern to scientists all over the world.Energy storage technology is springing up recent years,which can reduce energy waste.There are severial method to store energy,among which,Latent heat storage technology is a promising branch.When compared to other energy storage means,it has a high energy density,the system structure is simple and so on.Phase change materials are mainly divided into inorganic,organic and mixed.In this paper,the thermal storage properties of phase change materials are investigated.TBAB was used to study the cooling crystallization process of the aqueous solution of tetra butyl ammonium bromide with 20% initial concentration of TBAB in the air-conditioning system.And we studied the efficiency of preparation of TBAB hydrate slurry.Subsequently,a paraffin / foam copper composite phase change material was prepared,and a small thermal energy storage system test system was designed,and the water is used to transfer heat.The charge-discharge characteristics of the system was tested.In the application of direct temperature control,we established a three-dimensional numerical model to predict the thermal response of cold plate,which use paraffin or paraffin-containing composite phase change material as the core material.Effect of Thickness and Thermal Conductivity of the phase change material block was researched.In the actual application,numerical model can be firstly employed to calculate the required conditions,to help design the structure and specifications of regenerative units to reduce costs.The results are as follows:(1)the filter can prevent the crystal from flowing into the heat exchanger,which slows down the formation of the crystal layer on the wall of the heat exchanger,increasing the hydrate slurry concentration difference of the inlet and outlet.And the method with filter has COP 14.3% and 9.8% higher than those of homogeneous and nonhomogeneous storage,respectively.This method has a cost advantage over the mechanical scrubbing device provided in the heat exchanger.(2)Switch the floe by the flowrate is more suitable to melt the hydrate solid layer.(3)In the paraffin / foam copper energy storage system,it was experimentally proved that counter flow arrangement was better than that of parallel flow arrangement in the LTES system,which can speed up the heat transfer rate.Foam copper skeleton can greatly improve the thermal conductivity of PCM,heat transfer process PCM temperature is more uniform.(4)The inlet temperature and inlet speed will increase the energy storage system,and the efficiency is about 92-95%.because the system is so small that the change and discharge process are quickly accomplished.The time required to complete a charge or discharge process in most case is less than 50 min,so there is less heat loss.(5)PCM heat transfer way in charge process and discharge process are not the same way,the process of PCM energy storage in the natural convection mainly in the release process PCM heat conduction within the main.(6)When the thermal conductivity of the phase change core material is low,enhancing the thermal conductivity of the phase change can have a significant effect on the heat dissipation of cold plate,however,when the thermal conductivity of the phase change material exceeds 0.5W / m · K,the effect is weak(7)Increasing the thickness of the phase change block can increase the heat storage amount of the phase change cold plate,but it will also make it more difficult to transfer heat to the core of phase change block.So when design the thickness of phase change material block,severial elements must be take into consideration.