Effect Evaluation of Filling Medium Parameters on Operating and Mechanical Performances of Liquid Heavy Metal Heat Storage Tank

Abstract

In order to evaluate the feasibility and performance of liquid lead-bismuth eutectic as the heat transfer fluid for thermocline heat storage tanks in solar power systems, we conducted an effect evaluation of filling medium parameters on the integrated operating and mechanical performances of a thermocline tank using liquid lead-bismuth eutectic using the computational fluid dynamics simulation method. Four parameters were evaluated: the porosity, thermal conductivity, specific heat capacity, and equivalent diameter of the filling medium. The results show that the liquid lead-bismuth eutectic tank operated stably. The total charging and total discharging durations were 5.7 h and 5.3 h, respectively, and the discharging efficiency was 91.94%. The effect evaluation results reveal that the discharging thermocline thickness of the liquid heavy metal tank can be decreased by increasing the specific heat capacity of the filling particles, or by decreasing the porosity, thermal conductivity, and equivalent diameter of the filling medium. The total discharging quantity of the tank increased from 2.19 × 1010 J to 3.34 × 1010 J when the specific heat capacity of the filling particles increased from 610.0 J/(kg∙K) to 1010.0 J/(kg∙K), while the other three filling medium parameters had no obvious effect on the total discharging quantity of the tank. The mechanical performance of the tank wall could be improved by decreasing any one of the four evaluated parameters of the filling medium. The results of this paper may serve as a reference for the design of actual liquid heavy metal heat storage tanks in solar power plants.

A perspective on high‐temperature heat storage using liquid metal as heat transfer fluid

“…31 In further numerical works, the cyclic and standby behavior of a storage system with lead-bismuth and a packed bed with varied filler parameters and properties was theoretically analysed. [32][33][34] Recently, a packed-bed storage system with eutectic lead-bismuth as the heat transfer fluid has been demonstrated on a lab-scale (1 kWh) at KIT. A packed bed of ceramic fillers (zirconium silicate) was used with temperatures of up to 380 C. 35 The results showed that such a system is feasible and performs more efficiently than a single-medium thermocline storage tank with lead-bismuth only.…”

“…48 With a higher storage capacity, a longer discharge of the packed-bed storage can be realized assuming a fixed discharge power. 34 The increase of the packing density could be achieved by either a poly-disperse packed bed or optimized geometrical structures, as discussed in section 4.1.…”

“…When compared with liquid Na and solar salt in a packed‐bed storage, eutectic lead‐bismuth showed the highest efficiencies during discharge/charge and standby 31 . In further numerical works, the cyclic and standby behavior of a storage system with lead‐bismuth and a packed bed with varied filler parameters and properties was theoretically analysed 32‐34 . Recently, a packed‐bed storage system with eutectic lead‐bismuth as the heat transfer fluid has been demonstrated on a lab‐scale (1 kWh) at KIT.…”

“…With a higher storage capacity, a longer discharge of the packed‐bed storage can be realized assuming a fixed discharge power 34 …”