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Electronic Resource
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COO 2888 2; Report; February 1977.
Language
Library's review
ABSTRACT:
A five-task re search program aimed at the development of molten salt thermal energy storage systems commenced in June 1976. The first topical report, covering Task 1, the selection of suitable salt systems for storage at 850° to 1000°F, was issued in August 1976. We concluded that a 35
Interrelationships between various design parameters were examined using the available solutions, and an engineering-scale storage unit was designed. This unit has an annular configuration with a 1-foot OD, 1. 5-foot high, 2-inch diameter heat transfer well. Preliminary experiments on a pilot size (3-inch, OD) unit showed that temperature profiles and progress of the solid-liquid interface agreed with those predicted theoretically. Also, no supercooling was observed during cooldown, and the presence of significant convective mixing was indicated by negligible temperature gradients. Convective mixing is desirable because it allows higher heat transfer rates than those possible if the heat is transferred solely by conduction. Volume change for the LiKCO3 system was estimated to be ~10% between room temperature and the upper operating temperature. Use of a lithium aluminate volume-change suppressor was investigated, but it appears to be non-essential because of the low volume-change in the LiKCO3 system. Our consideration of the relative heat-transfer resistances under practical conditions suggested that the use of a conductivity promoter will enhance the heat-transfer rates, thereby requiring smaller heat-transfer areas. Different configurations and materials were considered for this application; an aluminum wool appears to be most suitable. We also investigated the corrosion resistance of various construction materials; stainless steels and aluminum appear to be suitable construction materials for carbonates in the 850° to l000°F range.
Testing of the engineering-scale system (Task 3) and verification of the conclusions derived under Task 2 are in progress at the present time.
A five-task re search program aimed at the development of molten salt thermal energy storage systems commenced in June 1976. The first topical report, covering Task 1, the selection of suitable salt systems for storage at 850° to 1000°F, was issued in August 1976. We concluded that a 35
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weight percent Li2CO3 -65 weight percent K2CO3 (LiKCO3 ) mixture was most suitable for the purpose. The present topical report, covering Task 2, describes our work on system design considerations. Interrelationships between various design parameters were examined using the available solutions, and an engineering-scale storage unit was designed. This unit has an annular configuration with a 1-foot OD, 1. 5-foot high, 2-inch diameter heat transfer well. Preliminary experiments on a pilot size (3-inch, OD) unit showed that temperature profiles and progress of the solid-liquid interface agreed with those predicted theoretically. Also, no supercooling was observed during cooldown, and the presence of significant convective mixing was indicated by negligible temperature gradients. Convective mixing is desirable because it allows higher heat transfer rates than those possible if the heat is transferred solely by conduction. Volume change for the LiKCO3 system was estimated to be ~10% between room temperature and the upper operating temperature. Use of a lithium aluminate volume-change suppressor was investigated, but it appears to be non-essential because of the low volume-change in the LiKCO3 system. Our consideration of the relative heat-transfer resistances under practical conditions suggested that the use of a conductivity promoter will enhance the heat-transfer rates, thereby requiring smaller heat-transfer areas. Different configurations and materials were considered for this application; an aluminum wool appears to be most suitable. We also investigated the corrosion resistance of various construction materials; stainless steels and aluminum appear to be suitable construction materials for carbonates in the 850° to l000°F range.
Testing of the engineering-scale system (Task 3) and verification of the conclusions derived under Task 2 are in progress at the present time.
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