Numerical Study on the Dynamic Performance of Combined Sensible-Latent Heat Packed-Bed Thermocline Tank

Abstract

Thermal energy storage (TES) using thermocline technology with phase change materials (PCM) is a promising technique for peak-shaving operation in cogeneration units. One of the disadvantages of this connotation is the use of the highly cost PCM capsules in a water tank. To circumvent this issue, a new thermocline tank connotation is proposed. The tank is packed with a mixture of solid filler pills and PCMs capsules, forming a multi-layered packed-bed system. A transient concentric-dispersion model is developed to assess the dynamic performance of a solid-PCM multi-layered packed-bed (SPMLPB) tank. The influences of the PCMs volume fraction (VF) and the charge and discharge dimensionless cutoff temperatures criterion on the dynamic performance have been investigated. The results show that the VF of PCMs influences the system's behavior, in terms of both energy storage and release. As the PCMs volume fraction increases from 10% to 40%, the amount of energy storage, energy release, and latent utilization ratio increased by 82.65%, 73.94%, and 55%, respectively, while the overall exergy efficiency drops by 6.3%. Besides, increasing both the charge and discharge cutoff temperatures criterion (STch*/STdisch*) enhances the total utilization ratio and energy recovered. When STch* increases from 0.27 to 0.7, the total utilization ratio and energy recovered increased by 63.63% and 28.67%, respectively, by maintains STdisch*=0.26.