Influence and optimization of building opening configurations on the performance of enhanced roof ventilation units (ERU): a numerical and orthogonal study

Enhanced roof ventilation units (ERU) can significantly enhance indoor airflow and thermal comfort, but their effectiveness is influenced by building opening configurations. Therefore, the performance of ERU under different building opening factors (window height (A), window size (B), door size (C), window orientation (D), door orientation (G), and building orientation (O)) was explored through numerical simulations and orthogonal design. Meanwhile, these factors influence laws, degrees, significance levels, and optimal schemes were identified. The findings reveal that: (1) For volume flow rate, the influence ranking is O > C > B > D > G > A, while for outlet average air age and volume air age, the rankings are O > G > A > D > C > B and O > A > G > C > D > B; (2) The indoor combinatorial ventilation efficiency under optimal configuration is 9.75 %, the flow purification rate and air exchange efficiency are 20.21 % and 48.27 %; (3) The percentage dissatisfied (PDT and PDD) under optimal configuration are 0.31 %; (4) Local vortices can lead to poor ventilation performance, but indoor circulation can bring the air exchange efficiency approaching the ideal 50 %. (5) The opening configurations focus on building orientation and dominant wind direction. (6) Appropriate opening configurations are more conducive to ventilation than increasing the area openings. This research provides valuable insights for optimizing roof ventilation units and improving indoor thermal comfort.