Effect of forced ventilation strategy on the thermal performance of finned-Trombe wall

Abstract

Compared with the natural ventilation (NV) strategy, the forced ventilation (FV) strategy has inherent characteristics. However, the research on the effect of FV strategy on the thermal performance of finned-Trombe wall (F-TW) is still lacking so far. To fill this gap, in this study, a 3D numerical model that only takes into account heat loss through the glass cover was created to evaluate the impacts of ventilation strategy, inlet airflow speed, fin geometric factors and external environmental parameters on the thermal performance of F-TW. The main findings demonstrate that the thermal efficiency ηth and exergic efficiency ηex under FV strategy first grow and then decline as the inlet airflow speed uin increases, with the extreme value appearing at around 0.50 m/s of uin. The optimal ηth and ηex can reach 99.76% and 14.89% respectively when the relative fin height h* = 0.90 and relative fin spacing s* = 0.02. ηth and ηex exhibit a tendency of steady growth with increasing h* and decreasing s*. The h* has a stronger impact on the thermal performance than s*. The FV strategy can not only improve the F-TW's thermal performance by effectively changing the flow and temperature fields in the channel, but also alters the variation law between s* and thermal performance. The optimal ηth and ηex are both increased by 39.18%, compared with the NV strategy, and 13.49%, in comparison to the case without fins. Improving the solar radiation intensity, reducing the outdoor ambient wind speed and increasing the outdoor ambient temperature are beneficial to the F-TW's thermal performance. Aiming at F-TW, the significance of this study is to provide the basis for the performance assessment under the FV strategy, as well as the selection of different ventilation strategies.