Numerical study on comprehensive performances of pipe-embedded building envelope integrated with arc-finned heat charging system

In the context of accelerating toward carbon neutrality, building envelopes are gradually regarded as multifunctional units with structural and energy attributes. To address the capacity mismatch between heat injection and thermal diffusion processes that hinder performance improvement of pipe-embedded energy walls, the arc-finned pipe-embedded energy walls (i.e., Arc-finPEWs) with directional heat-charging capacity are put forward. Subsequently, a validated mathematical model is established to explore the transient thermal behaviors of Arc-finPEWs as well as the impacts of 7 key parameters on its energy-saving potentials. Results showed that the directional heat-charging measures could improve the heat-charging capacity in specified directions, and the enhancement effect was more obvious as pipe spacing increased. Besides, the fin number (FN), shank length (SL), and fin angle (FA) were the top three influencing parameters in auxiliary-heating mode, whereas impacts of FA, FN, and arc angle (AA) ranked the top three in load-reduction mode. Furthermore, a larger FN and SL contributed to reducing total primary energy consumption and creating more robust invisible thermal barriers in auxiliary-heating mode, while left-facing fins or SL settings that are too high or too low were unfavorable in load-reduction mode. Meanwhile, the arc-fin designs with SL=0.6, FA=150° and AA=30° in auxiliary-heating mode and FA=30°, SL≤0.4 and AA≤15° in load-reduction mode are suggested. Compared to conventional energy-saving walls, the proposed arc-finned heat-charging system could reduce physical thermal insulation material usage with high embodied carbon features by over 60 %.