Numerical Simulation Of Thermal Storage Characteristics Of Spherical Multistage Phase Change Regenerator

In the process of energy development and utilization,there are intermittency,instability and time-efficiency differences.How to "shift peak and fill valley" and improve energy efficiency is an urgent problem to be solved.Heat storage technology can effectively adjust the imbalance of day and night power load of air conditioning,thus reducing the cost of generating electricity and improving the safe operation of power grid.It has been widely applied in HVAC all over the world.The heat storage unit is a key component of heat storage technology,so it is necessary to develop an efficient and stable latent heat accumulator.In the past,the enhancement of latent heat storage was mainly focused on shell,plate and column type accumulators.In this paper,a model of spherical multistage phase change heat storage unit was proposed on the basis of spherical heat storage unit.Using the existing phase change materials,the variation law of the heat storage process of the regenerative unit is studied by numerical simulation,and its characteristics during the process of heat storage melting and heat releasing solidification are analyzed.The heat storage characteristics of single phase variable materials are simulated and the effect of different wall thickness on the heat storage process was studied.The results show that the heat release and storage process of spherical single-phase variable material can be divided into three stages:initial stage,stable stage and stagnation stage.And the process of releasing heat is nearly 44.2%slower than the process of heat storage.The thickness of the fined material has little effect on the storage and release heat process.The characteristics of the thermal storage process of spherical multistage phase change heat storage unit are simulated.The result shows that,comparing with the data of spherical single-phase variable material storage unit,the thermal storage rate of spherical multistage phase change storage unit is increased by 25.8%and he rate of heat release slowed down by 3.2%.But from the point of view of the whole period of heat storage,the rate of heat storage accelerates 9.3%.The heat storage characteristics of spherical multistage phase change heat storage units with different heat transfer fluid temperatures,i.e.different boundary temperatures,are studied.The result shows that the increase of heat transfer fluid temperature can accelerate the heat storage rate.And the temperature increases by 10℃,the heat storage time increases by 21.6%.At the same time,with the decrease of the temperature of heat transfer fluid,the speed of releasing heat can also be accelerated.The recorded data show that the temperature is reduced by 10℃,the time of heat release process is shortened by 22%.The thermal storage performance of spherical multistage phase change heat storage unit with natural convection is studied.The results show that natural convection can accelerate the rate of heat storage by 28.1%and that of heat release by 32.6%.But heat conduction dominates the process of heat storage...