Simulation And Experimental Research On Ice Storage And Melt Process Of Ice Storage Coil

In recent years,with the development of the economy,the rapid growth of electricity consumption has caused a shortage of power supply during peak hours and a serious imbalance between peak and valley power supply.Especially in summer,a large amount of electricity is used for air-conditioning systems,and as their peak load periods match the peak hours of the city’s power grid,this makes the contradiction of insufficient power supply during peak hours even more pronounced.The external-melt air conditioning system has the ability to "shift the peaks and fill the valleys",which can solve this problem.The external-melt system is widely used in various practical projects due to its fast ice melt speed,low water discharge temperature and stable cooling process.This paper uses a combination of numerical simulations and experimental tests to study the ice storage and external-melt processes in a coil-type external-melt tank.Firstly,this paper tests the ice storage and external-melt process experiments by using external-melt experimental system and investigates the temperature distribution of the horizontal and vertical flow fields inside the ice storage tank and the variation of the ice volume outside the tube during these two experimental processes.The results show that there is temperature stratification within the trough.In addition,the water is subject to temperature flips in the vertical flow field due to natural convection.When ice is stored,the rate of increase of the ice volume in the tank decreases with the thickening of the ice layer.In the case of external melt,the rate of increase in ice melt remains high at the beginning of the melt and does not slow down until the end of the melt.In order to investigate the influence of the coil material on the ice storage performance and the characteristics of the ice distribution outside the tube during ice storage and external melting.In this paper,simplified models of horizontal single and multiple serpentine coils are developed and 3D transient simulations are carried out with CFD software.The ice storage simulation results of single tubes of different materials show that a small increase in thermal conductivity within a certain range can significantly improve the ice storage effect of the coils,but too large a thermal conductivity does not have a significant effect on the ice storage of the coils.In addition,the simulation results of ice storage and external-melt of multiple serpentine coils show that the ice layer between adjacent coils and at the elbow of the coils grows faster when ice is stored.When external ice melting occurs,the remaining ice outside the tube is distributed in an irregular circle,with the ice near the cold water intake area being the first to be completely melted to expose the bare tube.According to the distribution of the ice layer during the coil storage and external-melt,this paper proposes optimization measures for switching the refrigerant and the cold water flow direction and carries out a simulation comparison study.The simulation results show that the ice storage efficiency of a 2m long horizontal straight pipe is increased by 3.8% after changing the direction of the refrigerant flow,and the ice melting efficiency is increased by 5.9%after changing the direction of the cold water flow,which shows that this measure is more effective in improving the external-melt performance.The water distributor in the external-melt ice-on-tank ensures the uniformity of water distribution in the tank during ice melt,which has an important impact on the efficiency of ice melt.In order to study the uniformity of water distribution in the form of forward and reverse flow of the side vertical water dispenser,this paper simplifies the model of the water dispenser discharge structure for simulation and introduces the velocity deviation coefficient as the uniformity evaluation index.The results show a32.28% difference between the two velocity deviation coefficients,which indicates that the reverse flow water distributor has a better uniformity of distribution.