HVAC基本知识培训.ppt

常用风门 Dampers used in HVAC systems are typically air flow throttling devices and can be either modulating or two position. So it have two major type of damper actuator. They usually have multiple blades mounted on parallel shafts which are rotated in unison by an external actuator to change the blades from open to closed or closed to open Depending on the requirements of the system the assembly can be arranged as “normally open” or “normally closed” by means of the arrangement of the actuator device used to drive the damper Depending on how the adjacent shafts are linked together the damper assembly is either :- A parallel blade damper An opposed blade damper Parallel blade dampers are constructed so that each blade rotates in parallel with or in the same direction as the blade next to it Opposed blade dampers are constructed so that adjacent blades rotate opposite to each other The damper rotation increases the resistance to the air flow since the air is funnelled through a smaller opening An opposed blade damper must be open further than a parallel damper to obtain the same resistance to air flow 常用风门 常用风门 The following diagram shows a basic parallel blade damper assembly together with the air flow pattern with the damper at 33% closed 常用风门 The following diagram shows a basic opposed blade damper assembly together with the air flow pattern with the damper at 33% closed 常用风门 Round or butterfly dampers are typically used to control air flows in ducts that have high static pressure and high velocity characteristics 常用风门 Fire dampers are used to prevent superheated air, gases or flames from crossing a fire barrier. They can be duct mounted or installed directly in a fire barrier They are always two position devices 通风机 离心式 前曲式 后曲式 径向式 轴流式 离心风机 CENTRIFUGAL FANS Found in supply air applications and quietly move air at moderate pressures Utilise VSD drives for capacity control Older installations may have fans with inlet guide vanes to vary air flow Almost alwa