Effectiveness of enhanced roof ventilation unit (ERU) based on venturi cap in different wind environments and new evaluation models: A numerical study

Reasonable building ventilation design can effectively improve indoor thermal comfort and reduce energy consumption. Therefore, an enhanced roof ventilation unit (ERU) was developed for this study, and its performance and influence law under various wind speeds and directions were explored through numerical simulation. Additionally, a new evaluation method for ERU was proposed through data fitting, and applicability was verified for different climate zones in China. The results showed that: (1) With a maximum difference of 3.11 °C, the ERU performed best in the N direction and poorest in the SW direction for indoor temperature. Furthermore, the impact of wind directions was more evident than wind speeds. (2) The wind speed affected the volume flow rate significantly in the NE direction (7.77 m3/s) and insignificantly not in the SE direction (0.32 m3/s). Nevertheless, the performance was the opposite in the NE and SE directions when the wind speed increased from 0.5 m/s. (3) The air age performed best in the NE and worst in the SE directions. As wind speeds surpassed 2.0 m/s, the air age variation steadily stabilized in various wind directions. (4) The fitted equation for indoor temperature has applicability in typical cities in five climate zones, and the fitted equation for volume flow rate is applicable in four climate zones except the hot summer and warm winter zone. The study results can provide references for the ERU to improve indoor thermal ventilation, contributing to sustainable building energy efficiency.