Cross ventilation and the continuity equation

Abstract

In this work, ventilation in indoor environments is studied in the context of the Fluid Mechanics, a branch of Physics. Through the continuity equation for incompressible fluids, this work defines a ventilation factor: the air output velocity is the input velocity multiplied by the ventilation factor. Ventilation factor applications are illustrated in environments with two openings and within them. The ventilation factor is also used in estimate in environments with more than two openings. The paper also discusses the situation where the wind is damped by friction or accelerated by exhaust fans. The work opens perspective for the application of the ventilation factor in residential projects. The main result is that if the entrance area is larger than the exit area, the air leaves the environment faster than it entered; if the input area is smaller than the output area, the situation is reversed.