Optimization of packed-bed sensible heat storage systems based on a second law analysis

Journal
Applied thermal engineering  
Volume
300
Article Number
131220
Citation
Applied Thermal Engineering 300: 131220 (2026)
Publisher DOI
10.1016/j.applthermaleng.2026.131220
Scopus ID
2-s2.0-105037771382
Publisher
Elsevier
Packed-bed sensible heat storage (SHS) is important for balancing energy supply and demand over time. To improve the efficiency of a packed-bed SHS system through second law analysis (SLA), we developed multidimensional macroscopic entropy and exergy transport equations for fluid flow and heat transfer in porous media. These equations enable us to identify where and how much exergy is destroyed. Using a packed-bed SHS system developed at the PROMES-CNRS laboratory as a test case, we demonstrated how to apply SLA to optimize an SHS system. Our analysis revealed that, in addition to exit and heat leakage losses at tank surfaces, thermal and solid conduction losses inside the tank significantly contribute to total loss in the studied SHS system. These internal losses occur close to the thermocline. However, their slower transport causes a delay in their emergence. The SLA suggests an optimal tank aspect ratio of π·βˆ•π» = 0.75, at which the total exergy loss coefficient, πœπ‘ π‘‘π‘œπ‘‘, reaches its minimum value when exit loss is not considered. As particle size decreases, πœπ‘ π‘‘π‘œπ‘‘ also decreases due to enhanced heat transfer between the fluid and solid phases. The pressure loss for the studied SHS system is found to be negligible. The SLA favors a truncated cone-shaped tank with a slightly larger upper surface. Through the SLA, πœπ‘ π‘‘π‘œπ‘‘ is reduced by approximately 16.3% from 4.9% for the original design to 4.1% for the optimized design. This study demonstrates that, when used in conjunction with energy analysis, the SLA is an effective tool for optimizing energy storage systems.
Subjects
Computational fluid dynamics
Exergy
Porous media
Second law analysis
Sensible heat storage
Thermal energy storage
DDC Class
621: Applied Physics
530: Physics
Lizenz
https://creativecommons.org/licenses/by-nc-nd/4.0/
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