第1个回答 推荐于2017-10-12
vent is opening trough what air/gas/liquid /can flow.
if vent is closed, the flow is stopped or at least minimized.
if vent is open, the flow is it's maximum given the size of vent
if there is no air / gas / liquid pressure or temperature difference, no flow exists
do you want this in Hanzi, if s, feel free to ask.
(It is after all on foreign language study category, and I am writing this in a foreign language for both you and me)本回答被提问者和网友采纳