Comparative performance analysis of microchannel flat tube heat exchangers in thermochemical energy storage systems for water heating

Open thermochemical energy storage (TCES) systems are usually for air heating and need a design evaluation for their connection with domestic central hot water systems. Our prior research introduced a TCES water heating system that incorporates an internal embedded bare microchannel flat tube heat exchanger (i.e., IBHEX-TCES system). Although simulations confirmed its feasibility, operational and maintenance challenges were noted, particularly in large-scale, multilayer TCES systems. To address these challenges, this study numerically investigated a novel configuration of the TCES water heating system that integrates a detached finned microchannel flat tube heat exchanger (i.e., DFHEX-TCES system), enhancing simplicity in practice. The performance comparison under identical conditions shows that in most scenarios, water temperature rises achieved by the IBHEX-TCES system are slightly higher by up to 0.7 °C, while the DFHEX-TCES system consistently maintains a 10 to 15 percentage point lead in the system's discharging thermal efficiency. These findings also apply to multilayer TCES systems, demonstrating the feasibility and benefits of using DFHEX instead of IBHEX in multilayer TCES systems for large-scale applications. The use of DFHEX not only enhances the system discharging performance but also significantly eases operational and maintenance challenges.