Opposed-Movement Backdraft Damper Blades for Low Backpressure
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Solution Overview
Problem
Conventional backdraft dampers face challenges in maintaining airflow efficiency while preventing backdraft, as the force required to keep blades open reduces airflow rates and can lead to unintended leakage, compromising thermal protection and potentially allowing toxic gases into buildings.
Innovation Solution
The design incorporates two sets of blades that rotate in opposite directions, with one set being more balanced than the other, allowing the first set to open with minimal force and ensuring the damper remains closed under gravity, reducing energy loss and backpressure by directing airflow through an unobstructed intermediate flow region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If counterweights are used to keep damper blades open, then airflow is maintained, but the force required to keep blades open reduces airflow rates and can lead to unintended leakage
Solution Approach 1:
The damper blades are divided into two sets: first blades (more balanced) and second blades (less balanced with counterweights). This segmentation allows different balancing characteristics for different blade groups, enabling the first blades to open with minimal force while the second blades provide stable closing force, thereby maintaining airflow efficiency without excessive energy loss.
Solution Approach 2:
Different balancing properties are applied to different parts of the blade system. The first blades are designed to be more balanced about their pivot members, requiring minimal force to open. The second blades are designed to be less balanced with counterweights, providing gravitational force to keep the damper closed. This local differentiation optimizes both airflow efficiency and backdraft prevention.
2Reliability
If damper blades are kept open to maintain airflow, then thermal protection is compromised, but closing them prevents backdraft
Solution Approach 1:
The damper system dynamically transitions between open and closed states based on airflow conditions. During normal operation, the first blades open with minimal force to maintain airflow. When backdraft conditions occur, the second blades with counterweights automatically close the damper under gravity, providing reliable backdraft prevention without continuously sacrificing airflow.
Solution Approach 2:
The two sets of blades have asymmetric balancing characteristics. The first blades are more balanced for easy opening, while the second blades are less balanced with counterweights for reliable closing. This asymmetry allows the system to optimize for both airflow maintenance and backdraft prevention in different operational states.
3Productivity
If force is applied to keep blades open, then airflow efficiency decreases, but without force blades may not stay open
Solution Approach 1:
The blade system is segmented into first blades that require minimal force to open and second blades that provide gravitational closing force. This segmentation eliminates the need for continuous force application to keep blades open, improving airflow efficiency while maintaining ease of operation through automatic gravitational response.
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
This configuration enhances airflow efficiency by minimizing energy loss and maintaining effective backdraft prevention, ensuring the damper remains closed under disrupted outflow conditions without sacrificing airflow rates, thus improving HVAC system performance and safety.
Implementation Method 1
the one or more first blades being more balanced about respective pivot members than the one or more second blades thereby to permit the one or more first blades to bias the entire plurality of blades to the closed position
Implementation Method 2
movable to the open position by the force of air flowing through the frame in the outflow direction
Data Source
AI summary
A backdraft damper for permitting a flow of air in an outflow direction and preventing the flow of air in a backdraft direction, including a frame having a transverse opening allowing the passage of air through the frame; a plurality of blades, each blade extending across the frame and mounted to the frame about a central portion by pivot members, for rotation between an open position in which the blade allows air to flow through the frame and a closed position in which the blade blocks air from flowing through the frame, the plurality of blades including one or more first blades arranged to rotate in a first direction from the closed position to the open position; one or more second blades arranged to rotate in a second direction opposite to the first direction from the closed position to the open position; the backdraft damper further including a linkage between the one or more first blades and the one or more second blades to cause the first and second blades to together rotate between the closed and open positions; and the one or more second blades being more balanced about respective pivot members than the one or more first blades thereby to permit the one or more first blades to bias the entire plurality of blades to the closed position while being movable to the open position by the force of air flowing through the frame in the outflow direction.