A Phase Change Energy Storage Heat Exchanger For Recycling The Heat Of Middle Or Low Temperature Industrial Flue Gas

In industry,the recycling waste heat of intermediate and low with low energy quality is discharged directly and causing serious waste of energy.The heat of waste gas from China industry is so abundant that using the recycling waste heat is an important part in energy saving and emission reduction of production.This paper focus on the research of Phase Change Thermal Storage Heat Exchanger(PCTSHE)and the thermal storage efficiency improvement of PCTSHE and through experiment and numerical simulation,research the heat exchange tube structure's efficiency of different PCTSHE to heat transfer coefficient.Through comparing and analysing the time of Phase Change Material(PCM)complete fusion with different tube structure in PCTSHE,choose the heat exchange tube which has best performance of heat transfer in PCTSHE.The main research contents and conclusions are as follows:1.According to different character of different intermediate and low PCM,choose two intermediate and low PCMs which conform with the research of this paper.Through step cooling tests,then determine the phase transition of PCM,degree of subcooling,heat transfer homogeneity and phase transition stability of PCM,finally choose CH3COONa·3H2O as the experiment material of this paper.The CH3COONa 3H20's phase temperature is 57?,and it has large intent heat of phase change,stable phase transition properties,small degree of subcooling.2.According to the method of numerical simulation,use ANSYS-Fluent to established 12 Phase Change Thermal Storage(PCTS)unit models with different structure of heat exchange tube,simulate the phase transition process of different phase change unit,through calculating,get the different relation curve of liquid fraction with time change and the different curve of outlet gas temperature with time change when the different heat transfer unit melts.After comparing and analysing,it shows that phase-change heat transfer efficiency of the PCTS with finned tube is much larger than the PCTS with light tube,and best finned tube conforms with the requirements which the spacing of fin(L)are 6mm and the height of fin(H)are 4mm.Then according to best structure,use ANSYS-Fluent to establish integral Phase Change Heat Transfer(PCHT)models,the simulation result shows that the fulling melting time of material in the PCHT with finned tube decreases 19.9%than the fulling melting time of material in the PCHT with light tube,so the PCHT with finned tube has obviously effect to improve the efficiency of phase-change energy storage.3.To verify the simulation is right or wrong,design and make the U-tube phase-change heat transfer which tube pass is five,use CH3COONa·3H2O as the PCM,build the experiment platform which includes testing the related temperature of measuring point and flow at the processing of heat transfer.Comparing the result of experiment and simulation,it shows that the difference of fulling melting time between experiment and simulation is 25min and the error is 3.3%,so the result of simulation is right.