Butterfly Valve Pressure Averaging for Low-Flow Air Measurement
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Solution Overview
Problem
Existing butterfly valves in air-conditioning installations face high measurement inaccuracy at low volume flow rates due to a high spread of differential pressure, which affects control accuracy.
Innovation Solution
The butterfly valve features hollow chambers with recesses on each face, allowing differential pressure to be averaged across the flow duct's cross-section, enabling accurate measurement even at low flow rates, and includes measurement points connected to transmitters for precise control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate back-up elements are used to measure differential pressure, then the measurement device can handle maximum flow rates, but measurement accuracy deteriorates at low flow rates due to high spread of differential pressure
Solution Approach 1:
The butterfly valve face is segmented into multiple recesses (first, second, third, and fourth recesses) that divide the pressure measurement areas into separate zones. This segmentation allows each recess to capture pressure signals from different flow regions, and when combined, provide a stabilized differential pressure signal that maintains measurement accuracy across the entire flow range including low flow rates.
Solution Approach 2:
Different recesses are positioned to capture pressure signals from different local regions of the flow duct. The first and second recesses capture pressures from one side of the flow while the third and fourth recesses capture pressures from the other side. This local quality differentiation ensures that even when overall flow is low, each local region still provides measurable pressure signals that contribute to the overall accurate measurement.
2Measurement precision
If the butterfly valve is positioned at large throttle positions, then low duct velocities occur, but differential pressure signals become too weak for accurate measurement
Solution Approach 1:
The invention merges pressure signals from multiple recesses (first, second, third, and fourth recesses) to create a combined differential pressure signal. By combining these multiple pressure measurements, the system achieves sufficient signal strength even when duct velocity is low at large throttle positions, thereby maintaining measurement precision across the full range of valve positions.
3Measurement precision
If traditional back-up elements are used, then device structure remains simple, but control accuracy deteriorates due to high differential pressure spread
Solution Approach 1:
The butterfly valve is designed with multi-functionality by integrating both flow control and flow measurement functions into a single component. The recesses in the butterfly valve face serve dual purposes: they contribute to the valve's flow control function while simultaneously enabling accurate volume flow rate measurement through differential pressure detection, eliminating the need for separate measurement devices.
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 design provides high signal accuracy for both low and high air velocities, reducing pressure losses and ensuring reliable control under various flow conditions, including unfavourable onflow conditions.
Implementation Method 1
the differential pressure can be averaged over the entire cross section of the flow duct
Data Source
AI summary
The invention is a butterfly valve for a flow duct of an air-conditioning installation. The butterfly valve comprises two butterfly valve faces and is mounted for rotation about an axis. A device with at least two measurement points for determining the volume flow rate of a gaseous medium flowing in the flow duct is provided. In order to specify a butterfly valve, for example for a volume flow rate controller, which can determine a high differential pressure, even at very low volume flow rates, the butterfly valve comprises at least one hollow chamber on each of its two butterfly valve faces. Each hollow chamber has at least one recess, preferably with a multiplicity of recesses formed in the manner of a perforation. One measurement point is associated with one hollow chamber and the other measurement point is associated with the other hollow chamber.