Aircraft Cabin Ventilation Theory

Ventilation on board of an aircraft is governed by the ventilation equation. In the steady state case, a concentration of any substance depends only on the source strength and the effective air flow rate for ventilation. Not all air for ventilation is effective and helps to lower concentration. Some air leaves the cabin without mixing and rinsing. This is expressed by the ventilation efficiency. The dynamics follows an exponential function and is expressed by a time constant that depends on the air change rate and the ventilation efficiency. The (theoretical) air change rate is the air flow rate divided by the volume of the room. With full mixing (i.e. ventilation efficiency of 1), the concentration is reduced to 36.8% after one air change.

飞机机载通风系统遵循通风方程。在稳态工况下，任意物质的浓度仅取决于其源强与有效通风风量。并非所有用于通风的气流都能有效降低污染物浓度，部分气流未与舱内空气充分混合便直接排出机舱，这一特性可通过通风效率(ventilation efficiency)表征。系统的动力学过程遵循指数函数规律，可用取决于换气率与通风效率的时间常数进行描述。（理论）换气率为通风风量与机舱容积的比值。当气流实现完全混合（即通风效率为1）时，经过一次换气后物质浓度将降至初始浓度的36.8%。