Second law optimization of a sensible heat thermal energy storage system with a distributed storage element

Technical Report · Tue Jul 01 04:00:00 EDT 1986

DOI:https://doi.org/10.2172/5705807· OSTI ID:5705807

Taylor, M. J.

This numerical study defined the behavior of a sensible heat thermal energy storage system whose physical design and operation had been optimized to minimize the production of thermodynamic irreversibilities. It included the effects of transient conduction within the storage material. A dimensionless set of governing equations was defined for a complete storage-removal cycle that included the effects of entropy generation due to convection and viscous effects in the flowing fluid, two-dimensional transient conduction within the storage material, and to convection due to the discharged hot fluid coming to equilibrium with the environment during the storage period. A computer program was written to solve this equation set and this program was in turn controlled by a sophisticated optimization routine to determine a dimensionless storage time, flow channel half-height, and heat transfer coefficient that resulted in a minimum amount of availability destruction. The results of this analysis showed that entropy generation within the storage material due to transient conduction was a major contributor to the total thermal irreversibilities associated with the operation of a sensible heat thermal energy storage system. For the counterflow configuration and over the range of design variables examined, material entropy generation accounted for between 26% and 60% of the total thermal availability destruction that occurred during a complete storage-removal cycle. It was also shown that the storage material aspect ratio had a significant impact on the optimum design of a storage system. Its influence was second only to the fluid mass velocity.

• Research Organization: Oak Ridge National Lab., TN (USA)
• DOE Contract Number: AC05-84OR21400
• OSTI ID: 5705807
• Report Number(s): ORNL/TM-10054; ON: DE86013421
• Country of Publication: United States
• Language: English

Related Subjects

25 ENERGY STORAGE
250600* -- Energy Storage-- Thermal
COMPUTER CALCULATIONS
ENERGY STORAGE
ENTROPY
EQUIPMENT
HEAT STORAGE
MATHEMATICAL MODELS
OPTIMIZATION
PHYSICAL PROPERTIES
SENSIBLE HEAT STORAGE
STORAGE
THERMAL ENERGY STORAGE EQUIPMENT
THERMODYNAMIC PROPERTIES