Performance study of a thermochemical energy storage reactor embedded with a microchannel tube heat exchanger for water heating

Zhang, Yong; Hu, Mingke; Chen, Ziwei; Su, Yuehong; Riffat, Saffa

Abstract

Thermochemical energy storage (TCES) provides a promising solution to addressing the mismatch between solar thermal production and heating demands in buildings. However, existing air-based open TCES systems face practical challenges in integrating with central water heating systems and controlling the supply temperature. To overcome these limitations, a novel water-based TCES-HEX-HRU system is proposed in this study, which integrates a water-to-air microchannel tube heat exchanger (HEX) and an air-to-air heat recovery unit (HRU). A comprehensive evaluation of the TCES-HEX-HRU system is conducted numerically using a COMSOL model, including a comparative assessment for different TCES system configurations. The results demonstrate that the TCES-HEX-HRU system achieves an overall thermal efficiency of 82.35 %, marking a substantial 69 percentage points improvement over the TCES-HEX system. Although slightly lower than the typical air-based TCES system without HEX and HRU by 15.44 percentage points, the TCES-HEX-HRU system can be a practically promising and viable choice for applications in central heating systems. Numerical investigations indicate that the thermal performance of the system is influenced by the inlet conditions of airflow and waterflow. Moreover, increasing the number of water channels in the HEX of the TCES-HEX-HRU system enhances heat transfer but reduces the amount of heat released by TCES composite materials, resulting in a maximum overall thermal efficiency of 92.09 % with 35 channels and a peak outlet water temperature of 33.67 °C at with 30 channels. However, further increases in the number of channels lead to a decline in overall thermal efficiency and outlet water temperature. Changes in the width of water channels in the HEX have a minor impact on the highest outlet water temperature and overall thermal efficiency, while affecting the volume of the TCES composite materials.

• Journal Article Type: Article
• Acceptance Date: Dec 6, 2023
• Online Publication Date: Dec 12, 2023
• Publication Date: Feb 1, 2024
• Deposit Date: Jan 17, 2024
• Publicly Available Date: Jan 17, 2024
• Journal: Journal of Energy Storage
• Electronic ISSN: 2352-1538
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 78
• Article Number: 110043
• DOI: https://doi.org/10.1016/j.est.2023.110043
• Keywords: Thermochemical energy storage; Microchannel tube heat exchanger; Heat recovery; Thermal efficiency
• Public URL: https://nottingham-repository.worktribe.com/output/29539341
• Publisher URL: https://www.sciencedirect.com/science/article/pii/S2352152X23034424?via%3Dihub
• Additional Information: © 2023 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).