Numerical Simulation And Operation Characteristics Of Phase Change Thermal Storage Tank Based On Heating

With the rapid development of the social economy,energy demand continues to grow.In the process of energy utilization,there are many energy waste phenomena.Therefore,the importance of energy storage technology has become increasingly prominent.Phase change thermal storage technology,as one of the energy storage technologies,makes full use of the characteristics of high phase heat storage density,constant heat storage temperature and good thermal stability of materials,and has been widely studied and applied.With the gradual increase of the heating area in the north of China,the annual winter pollution caused serious pollution in the heating process,and increased the grid load.At present,domestic research on the application of thermal storage technology in heating has been carried out.However,the use of water for sensible heat storage is generally considered in heating.Compared with the sensible heat storage of water,the phase change heat storage material has the advantages of effectively reducing the volume of the heat storage tank,and the temperature of the heat storage and the heat release process is more stable.The phase change temperature of phase change heat storage materials studied at this stage is generally low,and it is only suitable for radiant heating in heating.In this paper,a heat storage material with a higher phase transition temperature is selected,which is suitable for radiant heating and radiator heating with air source heat pump and auxiliary electric heating as heat source,and thermal performance and phase change heat storage of phase change heat storage material.The research on the heat storage and heat release performance of the water tank was carried out.Firstly,an experimental study on the properties of composite phase change thermal storage materials with paraffin as phase change thermal storage matrix and expanded graphite as heat transfer carrier was carried out.When preparing a paraffin/expanded graphite composite phase change material,paraffin wax having a phase transition temperature of 64?is selected,and expanded graphite is added to enhance heat transfer performance.The effects of different types of expanded graphite and different mass fraction of expanded graphite worms on the heat storage performance of the materials were analyzed by experimental tests.The thermal properties of the materials were characterized by differential scanning calorimeter.The results show that the addition of 50 mesh expanded graphite worm with mass fraction of 3% can effectively improve the thermal conductivity of the material;the latent heat value of the 50 mesh expanded graphite sample with mass content of 3% is 203.1J/g;The material phase transition temperature is suitable for radiator heating near 64?.Then,the phase change hot water tank was designed,and the phase change heat storage system was established to study the temperature change during the heat storage and heat release of the water tank.The results show that the addition of 50 mesh expanded graphite worms with a mass fraction of 3% greatly improves the internal heat transfer efficiency of the phase change hot water tank,and the heat storage and heat release time is shortened by about 50%,and the expanded graphite worms The addition makes the phase change of the heat storage material in the phase change hot water tank more fully,and improves the utilization efficiency of the phase change material in the water tank.Finally,a phase change thermal storage model was designed with a straight tube unit of the phase change hot water tank,and numerical simulation and analysis were carried out in FLUENT software.By comparing the effects of fins,different inlet water inlet temperatures and different phase change materials on the temperature history of the phase change thermal storage unit during heat storage and exothermic process,it is concluded that the addition of fins makes the phase The heat storage and heat release efficiency of the variable thermal storage unit is increased by 60%;the higher the inlet water temperature,the faster the phase change material melts,and the longer the holding time of the higher temperature during the exothermic process;the addition of 3% of 50 mesh The model heat transfer efficiency of the composite phase change thermal storage material of expanded graphite is 50% higher than that of the phase change material pure paraffin.