The SPRD is used on zone systems when the automatic closing of various zone dampers can create an excessive increase in air pressure and velocity throughout the duct system.
SPRD旁通阀是当各种区域风门自动关闭时用在区域系统中，可以在管道系统中增加空气压力盒速度。
2
Finally, we give as an example the calculation of complex velocity potential for a twisted duct with square cross-section.
最后给出了一个方形扭曲管的复速度势计算实例。
3
The SPRD will automatically open as the air pressure in the duct system increases, in order to prevent the reduction of air flow and excessive noise and velocity through the duct system.