Mass Flow Controller Reservoir for Accurate Rate of Decay Measurement
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Solution Overview
Problem
Mass flow controllers face challenges in accurately measuring flow rates due to interference from Rate of Decay (ROD) measurements, which disrupt fluid flow and introduce temperature fluctuations, leading to inaccuracies, especially at low flow rates.
Innovation Solution
The system modifies the mass flow controller by increasing the inlet block volume and incorporating a reservoir with additional chambers or filler material to maintain fluid temperature constant during pressure decay, allowing for real-time correction and improved accuracy of ROD measurements without interrupting fluid flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ROD measurement is performed by interrupting fluid flow, then measurement can be conducted, but flow disruption and temperature fluctuations occur leading to measurement inaccuracies
Solution Approach 1:
The system divides the fluid flow path into separate segments: a measurement chamber for ROD measurement and a bypass channel for continuous fluid flow. This segmentation allows independent operation of measurement and flow functions, eliminating the conflict between measurement and flow continuity.
Solution Approach 2:
A temperature compensation mechanism acts as an intermediary to counteract temperature fluctuations during ROD measurement. The system uses temperature sensors and control algorithms to compensate for thermal effects, thereby eliminating the harmful temperature variations that would otherwise degrade measurement accuracy.
2Measurement precision
If inlet block volume is increased to improve ROD measurement accuracy, then measurement precision improves, but device complexity and size increase
Solution Approach 1:
The inlet block is segmented into functional zones: a enlarged measurement chamber for accurate ROD measurement and integrated bypass channels for continuous flow. This segmentation allows the volume increase to be localized only where needed for measurement accuracy, rather than increasing the entire device size.
Solution Approach 2:
The measurement chamber and bypass channel are merged into a single integrated inlet block structure. This combining allows the system to achieve both functions (accurate measurement and continuous flow) within one component, avoiding the need for separate external components that would increase overall device complexity.
3Measurement precision
If ROD measurement is performed, then flow rate calibration can be achieved, but measurement time increases especially at low flow rates
Solution Approach 1:
The system performs preliminary temperature stabilization and pressure equilibrium before initiating the ROD measurement sequence. This preliminary action ensures that measurements start from a stable baseline, reducing the time needed to achieve accurate results particularly at low flow rates where measurements would otherwise take longer.
Solution Approach 2:
The bypass channel maintains continuous fluid flow throughout the ROD measurement process, allowing the measurement to proceed without interrupting the useful flow action. This continuity enables faster measurements compared to traditional methods that require complete flow interruption and longer stabilization periods.
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 approach enhances the accuracy of ROD measurements by minimizing flow disruptions and temperature-induced errors, enabling precise flow rate determination even at low flow rates, with reduced run times and improved reliability.
Implementation Method 1
incorporating a reservoir with additional chambers or filler material to maintain fluid temperature constant during pressure decay
Implementation Method 2
a pressure sensor that generates a pressure sensor signal that is proportional to the pressure of the fluid in the conduit
Implementation Method 3
at least one flow sensor that generates a flow sensor signal that is proportional to the flow rate of the fluid through the conduit
Data Source
AI summary
A mass flow controller includes at least one conduit having a fluid inlet and a fluid outlet, the conduit defining a flow path along which the fluid flows. The mass flow controller also includes a modified inlet block having an inlet aperture, an inlet channel, and a reservoir fluidly coupled to the inlet channel and the conduit that enhances flow through the controller and improves rate-of-decay measurements. The mass flow controller includes at least one flow sensor that generates a flow sensor signal that is proportional to the mass flow rate of the fluid through the conduit. The mass flow controller includes a control subsystem coupled to a flow sensor and a valve assembly to control flow through the conduit.