A comprehensive study on transient thermal behaviors and performances of the modular pipe-embedded energy wall system under intermittent operation conditions

Abstract

The active thermal insulation technology based on utilizing low-grade thermal energy makes the opaque envelopes gradually be treated as multifunctional components with structural and energy properties. In this study, the dynamic thermal behaviors of modular pipe-embedded energy (MPE) walls integrated with pipe installation cavity and backfilling material are numerically studied, and then the impacts of key variables on MPE walls are explored. Results show that the thermal behaviors of MPE walls can be significantly improved under all intermittent charging modes, while the maximum extra heat loss caused by applying filler cavity and backfilling material is only 2.4%. When the injection time is kept constant, MPE walls operated in multi-pulse modes, especially those with higher heat injection frequency (e.g., 3On3Off mode), can achieve a better performance enhancement and operating energy reduction effect. Besides, a reasonable increase in λf-value or a:b-value can effectively alleviate the heat accumulation around water pipes. In addition, the energy consumption of heat charging systems can be significantly reduced when performance indicators can be slightly sacrificed. Results highlight the effectiveness of adding pipe cavity and backfilling materials in enhancing the performance of MPE walls, which can provide theoretical guidance and data support for such walls in the future.