Performance Experiment And Enhanced Heat Transfer Analysis Of Mobile Thermal Storage System

There are a lot of waste heat resources in China's industrial production every year,and the use of low-temperature waste heat resources is most difficult.On the other hand,With the rapid development of urbanization in China,and the growing of heating requirement,Some users rely on small self-contained boilers to produce heat,not only inefficient,but also cause great pollution.Mobile thermal storage technology can transport the waste heat resources to users by the mobile thermal storage car.It has great significance to China's energy-saving emission reduction policy.In this paper,for the waste heat below 100?,made the following study:A lab-scale thermal storage system(TSS)was set up with the Ba(OH)2·8H2O as main material according to the principle of mobile thermal storage technology.The charging and discharging experiments with TSS were carried out.The experimental study shows that : the temperature difference of PCM along the heat transfer fluid(HTF)flow direction is small,but the temperature difference of PCM perpendicular to the HTF flow direction is relatively large.The TSS absorbed 57670 kj heat from the heat source to complete melting in 120 min,and released 35098 kj heat to complete solidification in 100 min.The overall thermal efficiency(include charging and discharging)was 60.8%.In order to simulate the actual working conditions,the temperature variation and the temperature between import and export were analyzed.The performance of the TSS was studied with two indexes: thermal efficiency and exergy efficiency.It is concluded that the application of mobile thermal storage technology is more favorable when the temperature of the heat source is higher.And in order to avoid the waste of energy,we should control the velocity of HTF to prevent the phenomenon of excessive velocity.Due to the limited measuring points in experiment,simulation of charging and discharging processes was conducted to further understand the melting and solidification.The models were built based on the assumptions and simplifications of experiment.They were verified by comparing the calculated results with those of experiment.The variation law of the phase interface of PCM and the change of the liquid phase rate with time were analyzed,and the melting and solidification "dead area " existing at the near wall of the TSS is obtained.Finally,the heat transfer of the TSS was analyzed.The analysis showed that the thermal energy system had the fastest melting and solidification rate when the heat transfer tube is a triangular uniform way.And the size of the heat transfer diameter had little effect on the melting and solidification rate of PCM.To solve the problem of melting and solidification "dead area " in the thermal energy system,it was proposed to optimize the structure of the TSS by changing the diameter and local encryption,and achieved remarkable results to make it melting and solidification "dead area " significantly reduced,the time of complete the melting and solidification reduced by 35% and 22%.