Thin Film Thermal Mass Flow Sensor for Low Flow Leak Detection
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Solution Overview
Problem
Existing flow sensors struggle to detect low magnitude leaks in larger pipe sizes due to compromised low flow sensitivity, and current methods like pressure decay tests and bypass loops are not real-time or efficient.
Innovation Solution
A thin film thermal mass flow sensor is designed with a substrate supporting a resistive heating circuit and temperature sensor circuits, bonded to a thermally conductive membrane, which can be oriented to detect fluid flow accurately in larger pipes, allowing for real-time detection of low flow rates without interrupting fluid flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a traditional flow sensor is installed in larger pipe sizes, then the flow meter can measure fluid flow in larger pipes, but the low flow sensitivity is compromised and low magnitude leaks cannot be detected
Solution Approach 1:
The flow sensor is segmented into a separate bypass loop system. Instead of placing the sensor directly in the large pipe, a portion of the fluid flow is diverted through a smaller bypass loop where the thin film thermal mass flow sensor is installed. This allows the sensor to operate in a smaller effective flow area while still monitoring the overall system flow, thereby maintaining low flow sensitivity even when installed in larger pipe systems.
Solution Approach 2:
A bypass loop acts as an intermediary between the large pipe system and the flow sensor. The bypass loop with check valve directs a controlled portion of the main flow through the sensor, enabling accurate measurement of low flow rates without requiring direct installation in the large pipe. This intermediary structure resolves the contradiction between pipe size and measurement sensitivity.
2Reliability
If a pressure decay test is used to detect leaks, then leak detection can be performed, but the system requires valve installation and interruption of fluid flow with long monitoring time
Solution Approach 1:
The thin film thermal mass flow sensor enables continuous real-time monitoring of fluid flow without interrupting the flow itself. Unlike pressure decay tests that require flow interruption and extended monitoring periods, this sensor provides ongoing leak detection as fluid flows continuously through the system, eliminating downtime and maintaining operational continuity.
Solution Approach 2:
The mechanical pressure decay test system (requiring valves, pressure sensors, and flow interruption) is replaced with a thermal-based flow sensing system. The thin film thermal mass flow sensor detects leaks by measuring thermal effects of flowing fluid, substituting the complex mechanical test procedure with a simpler, continuous thermal measurement approach that requires no flow interruption.
3Measurement precision
If a bypass loop with check valve is used to detect minimal flow leaks, then low flow rates can be directed through the sensor, but the system complexity increases with additional valves and loops
Solution Approach 1:
The bypass loop with check valve serves multiple functions simultaneously: it directs low flow rates to the sensor for accurate measurement, isolates the sensor from high pressure fluctuations in the main line, and enables continuous monitoring without affecting the main flow path. This multi-functionality justifies the added components by providing several benefits from a single integrated structure.
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 sensor effectively detects low flow rates in larger pipes by using a thermally conductive membrane and resistive heating circuit, providing real-time monitoring without the need for valve installation or long monitoring times, enhancing leak detection sensitivity and efficiency.
Implementation Method 1
a resistive heating circuit disposed between the first and second temperature sensor circuits
Implementation Method 2
A thermally conductive membrane 40 is configured to separate the fluid flow of the liquid inside the pipe portion from the thin film thermal mass flow sensor
Implementation Method 3
a first temperature sensor circuit 36 and a second temperature sensor circuit 37 on the upper side of the substrate
Data Source
AI summary
A flow sensor configured to detect a fluid flow of a liquid inside a pipe portion is disclosed. A thin film thermal mass flow sensor has a substrate defining a thickness from an upper side opposite a bottom side. The upper side of the substrate supports a resistive heating circuit, a first temperature sensor circuit and a second temperature sensor circuit. The resistive heating circuit is disposed between the first and second temperature sensor circuits. The circuits are electrically connected respectively to a plurality of leadwires configured to be attachable to electronic equipment. A thermally conductive membrane is configured to separate the fluid flow of the liquid inside the pipe portion from the thin film thermal mass flow sensor. A thermally conductive bond connects the bottom side of the substrate of the thin film thermal mass flow sensor to the thermally conductive membrane.