Airflow velocity in the section

## Method Formulas: ```text A_face = (W / 1000) × (H / 1000) [m²] v_face = Q / (3600 × A_face) [m/s] with k_open entered: A_free = A_face × k_open [m²] v_free = Q / (3600 × A_free) [m/s] ``` ## Worked example Q = 7200 m³/h, W = 1000 mm, H = 500 mm → A_face = 0.5 m², **v_face = 4 m/s**. With k_open = 0.8 entered by the engineer → A_free = 0.4 m², **v_free = 5 m/s**. The numbers in the tool must match. ## Limitations - v_face is the average velocity in the face section; the velocity in individual vane channels is higher and is determined by the model data sheet. - k_open is not universal: it depends on the profile and pitch of the specific model and is entered by you manually. - The tool does not check whether the velocity is allowable for a specific model — comparison with the maximum velocity is possible only with a data sheet. ## Related tasks - size the section for a target velocity — "Required section size"; - estimate ΔP from the data sheet ζ — "Pressure drop ΔP".