6月份，Hog Slat美国总部通风主管Austin Baker分享了隧道通风系统故障排除指南，通俗而易懂，简单易操作。今天， Austin Baker，继续为大家分享通风系统中，不同类型的百叶窗对风机的性能产生哪些不同的影响。猪场建设，选择设备很重要，选择合适的设备更加重要。
请看下文内容：
Learn how different types of shutters affect fan performance（By Austin Baker, ventilation director, Hog Slat Inc.）
了解不同类型的百叶窗对风机性能的影响（Austin Baker, Hog Slat通风主管）
Shutters are an accessory item used to seal off backdrafts when the fan is not operating. Air flows to a fan from inside the building and exits the fan in a spinning pattern.
百叶窗是在风机不工作时用来阻止反向气流进入舍内的密封部件。舍内气流流向风机，通过扇叶形成旋转气流排出舍外。
Because a shutter disrupts the flow of air through the fan, we can expect a 10 to 25% reduction in cubic fee per minute delivery depending on the type and location of the shutter. The force required to open and maintain a shutter in the open position also decreases air delivery.
因为百叶窗会破坏流向风机的气流，根据不同的百叶窗类型和安装位置，风机风量会衰减10%~25%。同时气流通过百叶窗并使百叶窗保持打开状态也会降低风量。
The most common type of shutter used with agricultural exhaust fans is a vertical vane in either aluminum or plastic.
农业风机最常用的百叶窗类型是铝制或者塑料材质的垂直叶片型。
Aluminum shutters typically are connected with a tie bar, so they open together to prevent flapping. Damage to one of the vanes can cause the shutter not to open completely causing airflow to be restricted. Plastic shutters have individual vanes, are corrosion resistant, and their lighter weight reduces the amount of force to keep them open.
铝制百叶窗叶片一般会通过一个拉杆连接在一起，因此当百叶窗打开时，所有叶片全部打开，防止百叶窗打开时发生拍动。因此其中一个叶片的损坏都会导致百叶窗不能完全张开，造成气流不能正常排出。塑料材质的百叶窗叶片都是独立的，耐腐蚀，重量也更轻，更加容易保持叶片张开。
(Image: Exterior Shutter Caption: Placing the shutter on the exit side of a fan blade disrupts air airflow and reduces output by 15 to 25%)
（图：百叶窗外置示意图：将百叶窗安装在风扇叶片的出口侧，会破坏空气气流，减少15-25%的风量）
Placing a shutter on the exit side of a fan interrupts the spiral motion of the air leaving the fan blade causing backpressure. We can expect a 15 to 25 % reduction using exterior-mounted shutters.
将百叶窗安装在风机出风口侧，会阻止排出气体形成旋涡状气流，造成反向气压。我们可以推断这样的安装方式会减少15-25%的风量。
Moving the shutter to the intake side of the fan improves air delivery as the disruption to the air stream occurs before the fan blade. Mounting a shutter in an interior position only reduces air delivery by 10 to 15%.
将百叶窗安装在风机进风口侧，由于在气流流向扇叶前就将气流阻断，可以改善气流输送。这样安装百叶窗只会减少10-15%的风量。
Butterfly shutters consist of a circular damper with a vertical hinge mounted on the fan exterior. Butterfly shutters increase airflow by over standard louvered shutters as they offer very little resistance to air flow once they are open. Expect performance increases of 10 to 20% over interior-mounted shutters. This advantage increases when dust accumulates; butterfly shutters are not affected by dust buildup to the same extent as louvered shutters.
碟形百叶窗由一个带垂直铰链的圆形挡板组成，安装在风机出风口侧。碟型百叶窗打开时对气流的阻力非常小，因此对风量的改善比普通百叶窗要好。与进风口侧安装的普通百叶窗相比，蝶形百叶窗能提高10%~20%的风量。考虑到灰尘积聚的影响，碟型百叶窗的优势会更加明显，因为碟型百叶窗不像一般百叶窗一样容易受到灰尘积聚的影响。
Butterfly shutters, however have one significant disadvantage. During cold weather, condensation forms on the interior of the fan housing, including the motor and drive system. Over time this increased moisture can cause accelerated deterioration of the fan components. With interior-mounted shutters the condensation forms on the shutter keeping the fan housing drier.
然而碟型百叶窗也有一个明显的缺点。天气寒冷时，风机壳体内壁、电机以及传动系统会形成冷凝水，导致风机部件加速老化。而安装在舍内的百叶窗，冷凝水只产生于百叶窗上，风机外壳是干燥的。
One final thought, a dirty shutter robs up to 8% of a fan's cfm delivery because of the extra energy required to keep the vanes open. No matter what type of shutter is installed on a fan, keeping it clean and dust-free pays dividends.
最后一个重要点是，百叶窗变脏会导致8%左右的风量流失，因为保持风机叶片打开需要消耗额外的能量。因此，无论风机安装哪种类型的百叶窗，保持百叶窗的清洁和无尘都是重要的。
References
文献参考
1.Fabian, Eileen E. 2016. Selecting Rated Ventilation Fans. Professor of Agricultural Engineering. Penn State University.
Fabian, Elieen E.2016年.【通风系统风机选择】.宾夕法尼亚州立大学农业工程教授.
2. Czarick, Michael. No date. Improving Tunnel Ventilation Fan Energy Efficiency. Department of Poultry Science. The University of Georgia.
Czarick,Michael. 无具体日期.【提高隧道通风风机能效】.佐治亚大学家禽学系.
