Cyclic behaviors of the molten-salt packed-bed thermal storage system filled with cascaded phase change material capsules. (25th January 2016)

• Record Type: Journal Article
• Authors: Wu, Ming; Xu, Chao; He, Yaling
• Is Part Of: Applied thermal engineering. Volume 93(2016:Jan.)
• Page Start: 1061
• Page End: 1073
• Publication Date: 2016-01-25
• Subjects: Thermal energy storage -- Solar energy -- Packed bed -- Phase change material; Heat engineering -- Periodicals; Heating -- Equipment and supplies -- Periodicals; Periodicals; 621.40205
• DOI: 10.1016/j.applthermaleng.2015.10.014
• Languages: English
• ISSNs: 1359-4311

Abstract

Highlights: Cyclic behaviors of a TES system packed with cascaded PCM capsules are investigated. Non-cascaded system suffers from a low charging ratio and a long charging time. The cyclic process of the cascaded system can reach to a repeatable state after some cycles. Practical storage capacity depends on the threshold temperature to stop the operation. Abstract: A transient, one-dimensional dispersion-concentric model to numerically study the cyclic behaviors of the molten-salt packed-bed thermal energy storage system filled with cascaded phase change material (PCM) capsules is presented. Three different storage systems are investigated which include the non-cascaded system, the cascaded systems with 3 and 5 cascaded phase change temperatures (PCTs). Detailed characteristics of heat transfer between molten salt and the packed PCM capsules are discussed, and various numerical results are presented, including the temperature distributions of molten salt and PCM capsules, the variations in the molten-salt outlet temperature, the accumulated efficiency of each cycle. The results show that the non-cascaded system suffers from a low charging ratio and a long charging time due to the constrains of PCT while the cascaded systems especially with 5 cascaded PCTs are found to have both a fast discharging rate and a fast charging rate. The cyclic process of the cascaded system with 5 cascaded PCTs can reach to a repeatable state after some cycles, at which high accumulated efficiencies can be achieved. It is also found that the practical storage capacity of the storage system with cascaded PCM capsules depends highly on the threshold temperatures to stop the charging/discharging process.