| In traditional integrated energy services projects,energy storage is typically achieved by building one or more individual storage pools in the greenbelt near the power station,but it takes up lots of space.Using the existed underground building to design the energy storage pool,not only saves the building space,reduces the initial investment cost,but also does not affect the environment.However,the conventional energy storage pool simply divides the underground space into several energy storage units with partitions,and water flows through each unit successively in the horizontal direction,resulting in serious natural convection phenomenon,which makes the energy storage efficiency not high.Therefore,it is of great significance to design an energy storage tank for underground space structure and to study the flow,heat transfer and energy storage characteristics of energy storage working medium.In this paper,a design idea of maze-type energy storage pool is developed,that is,a traditional rectangular energy storage pool is formed by setting a baffle to form the energy storage unit,and then according to the structure of underground space,the order of the energy storage unit is flexibly adjusted to form the variable shape of the energy storage pool.Using numerical method to simulate the water in the single tank energy storage tank,tank storage pools and labyrinth process of flow and heat transfer in energy storage tank,analyses the structure parameters and operating parameters on the flow velocity distribution and the influence law of temperature distribution,explores the labyrinth energy storage characteristic of mixed area and the pool overall energy changes,labyrinth energy storage pool storage characteristics optimization method is studied.The main work and conclusions are as follows:Firstly,the physical model and mathematical model of the single storage tank were established,and the accuracy of the simulation method was verified by comparing with the experimental conditions in the literature.The influence of different structural parameters and operating parameters on the proportion of thermocline layer in the storage tank was studied.The results show that the thickness of thermocline layer increases with the process of energy storage,but the increasing rate becomes slow.The proportion of thermocline decreases gradually with the increase of tank height,The proportion of thermocline layer decreases gradually with the increase of the installation height of diffuser,the proportion of thermocline layer increases gradually with the increase of inlet velocity.the proportion of thermocline layer increases gradually with the increase of temperature difference between inlet and outlet.Then,based on the single-tank energy storage tank,a separator is set to form a storage unit.The flow and heat transfer characteristics of the working fluid in the multi-tank energy storage tank formed by the combination of three storage units are studied.The effects of structural parameters and operating parameters on the velocity and temperature non-uniformity coefficients are analyzed.The results show that eddy current exists when water enters different energy storage units due to the structure of multi-tank energy storage pool,which leads to great velocity heterogeneity in the energy storage units.The average temperature in the whole energy storage pool decreases continuously with the continuous progress of the energy storage process,and the decreasing speed is relatively uniform.The velocity inhomogeneity coefficient decreases with the increase of partition spacing,and the variation law of temperature inhomogeneity coefficient is consistent with velocity inhomogeneity coefficient.,The velocity unevenness coefficient decreases gradually with the increase of the partition height,and the variation law of temperature unevenness coefficient is consistent with the velocity unevenness coefficient.The velocity inhomogeneity coefficient gradually decreases with the increase of velocity,and the variation law is consistent with the velocity inhomogeneity coefficient.With the increase of energy storage temperature difference,the half-cycle perfection decreases.Finally,based on the above research results,the flow field was optimized by means of flow guide plate and porous plate,and the variation law of flow field and temperature field in the optimized multi-tank energy storage tank was studied.The energy storage characteristics of typical labyrinth energy storage tanks,such as U-shaped,L-shaped and concave,before and after optimization were further studied.The results show that both the guide plate and the porous plate can make the flow field more uniform,but the optimization effect of specific location and structure is different.With the increase of the radius and installation height of the guide plate,the velocity inhomogeneity coefficient first decreases and then increases.With the increase of the distance between the guide plate and the inlet,the velocity inhomogeneity coefficient decreases gradually.Under the condition with the best flow sharing effect,the maximum ratio difference of mixing zone can be reduced from24.6% to 23.8%.With the increase of the mounting height of porous plate,the velocity inhomogeneity coefficient increases gradually.With the increase of opening rate,the velocity inhomogeneity coefficient decreases first and then increases.Under the condition with the best flow sharing effect,the maximum ratio difference of the mixing zone can be reduced from 24.6% to 23.1%,which is better than that of the guide plate.The ratio of the mixing area of the energy storage pool has a great influence on the energy change law of the labyrinth energy storage pool.After optimization,the maximum difference value of the mixing area of the U-shaped,L-shaped and concave energy storage pools decreased by 2%,1.95% and 2.08%,respectively.The total period effective cooling capacity increased by2394.173 k J,2278.653 k J and 2473.846 k J. |
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