Spring-Biased Exhaust Fan Damper for Wind-Resistant Backdraft Control
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Solution Overview
Problem
Existing fan systems in animal confinement and other ventilation applications fail to prevent backdraft and pathogen infiltration, especially when not running or operating at low speeds against strong winds, leading to potential disease transmission and reduced efficiency due to pressure drop issues.
Innovation Solution
A damper flap mechanism is integrated into fan housings, which automatically closes when the fan is not running to prevent backdraft and partially opens when running at low speed to counteract wind forces, while fully opening at high speed to maximize airflow, utilizing a biasing arrangement and seal design to minimize airflow restriction and maintain airtightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the damper flap is kept closed to prevent backdraft when the fan is not running, then pathogen infiltration is prevented, but airflow restriction occurs when the fan should be operating
Solution Approach 1:
The damper flap is designed to be dynamic rather than static, automatically adjusting its position based on fan operation status. It closes when the fan is off to prevent backdraft, and opens when the fan operates to maximize airflow, thus resolving the contradiction between backdraft prevention and airflow capacity
Solution Approach 2:
The system incorporates feedback mechanisms (such as pressure sensors or mechanical linkages) that detect fan operation status and automatically control the damper flap position accordingly, ensuring the flap closes when the fan is off and opens when the fan is on, eliminating the need for manual intervention
2Productivity
If the damper flap is fully open to maximize airflow at high fan speed, then airflow capacity is improved, but backdraft control is reduced when wind forces are strong
Solution Approach 1:
The damper flap position is adjusted as a variable parameter based on operating conditions. At high fan speeds, the flap is fully open to maximize airflow capacity, while at low fan speeds or high wind conditions, the flap position is modified to maintain backdraft control, thus optimizing both airflow and protection
3Reliability
If the damper flap is held partially open to counteract wind forces at low fan speed, then backdraft is prevented, but pressure drop increases reducing fan efficiency
Solution Approach 1:
The damper flap is held partially open rather than fully open at low fan speeds, providing just enough opening to counteract wind forces and prevent backdraft while minimizing the pressure drop and energy loss, thus applying partial action to achieve the minimum necessary protection
4Device complexity
If a simple gravity-closed damper is used, then device complexity is reduced, but the damper cannot maintain controlled opening at intermediate positions against wind forces
Solution Approach 1:
The system prepares for wind forces by incorporating biasing arrangements (springs or weights) that pre-position the damper flap to resist wind forces before they act on the system, enabling the flap to maintain controlled opening positions without requiring complex active control mechanisms
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively prevents backdraft and pathogen infiltration, increases fan efficiency by reducing pressure drop, and enhances airflow exhaust capacity, resulting in improved air quality and reduced energy consumption.
Implementation Method 1
providing a biasing arrangement for applying force to the damper flap, the biasing arrangement being arranged on one side of the intermediate position adjacent the closed position to bias the damper flap into the closed position and on an opposed side of the intermediate position adjacent the fully open position to bias the damper flap into the fully open position
Implementation Method 2
utilizing a biasing arrangement and seal design to minimize airflow restriction and maintain airtightness
Data Source
AI summary
An extraction fan has a housing mounted in a wall with an outlet duct extending through the wall to an outlet opening outside the wall. A damper flap is mounted on the fan suspended by a hinge at an upper edge so as to extend in a closed position across the opening and is movable to an open position under forward air flow from the fan, and tightly closes against a resilient deformable seal when the fan is shut off. A spring biasing cam applies inwards force to the damper flap to bias the damper flap into the closed position, and an outwards force also to bias the damper flap into the fully open position. The mounting plate includes a hood having a top wall extending over the top of the damper flap and a down-turned front flange extending parallel to the damper flap to a bottom edge.