Thermal Flow Sensor Membrane Design for Turbulence Reduction
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Solution Overview
Problem
Conventional thermal flow sensors face challenges in achieving high mechanical stability while minimizing turbulence and thermal mass, leading to imprecise measurements due to the need for thick substrates and unfavorable vortex formation.
Innovation Solution
A thin metallic substrate with a cutout forming a membrane is used, where a dielectric layer reduces thermal coupling between the heating and temperature sensor elements, and a layered composite dielectric structure enhances thermal conductivity and mechanical stability, allowing for precise and sensitive measurements with reduced environmental disruption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If thick substrates are used to ensure mechanical stability, then mechanical stability is improved, but turbulence increases and measurement precision deteriorates
Solution Approach 1:
The patent employs a composite structure consisting of a thin metallic substrate (50-200 μm thick) combined with a membrane structure. The metal substrate provides mechanical stability while the membrane reduces thermal mass and turbulence. This composite approach allows the sensor to achieve both mechanical strength and measurement precision by combining materials with complementary properties.
2Measurement precision
If membranes are used to reduce thermal mass, then thermal mass is reduced and measurement sensitivity is improved, but substrate thickness increases causing turbulence
Solution Approach 1:
The patent uses a thin membrane structure formed on the metallic substrate to reduce thermal mass in the flow-sensitive area. The membrane allows heat to transfer efficiently to the flowing medium while maintaining a low profile that minimizes turbulence. The thin film approach enables the sensor to be aerodynamically streamlined, reducing unwanted flow disturbances.
Solution Approach 2:
The patent optimizes the thickness parameter of the metallic substrate to a specific range (50-200 μm, preferably 50-100 μm). This parameter optimization balances mechanical strength requirements with the need to minimize overall sensor height and reduce turbulence generation in the flow channel.
3Measurement precision
If thermal decoupling is implemented using membranes, then measurement sensitivity is improved, but device complexity increases
Solution Approach 1:
The patent combines multiple functions into the membrane structure: it serves as both the thermal decoupling element and the support for heating/temperature sensor elements. The membrane integrates structural support, thermal management, and sensor mounting functions, reducing overall device complexity while maintaining measurement sensitivity.
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 enables precise and fast measurements with minimal turbulence, maintaining high mechanical stability and efficient heat transfer, thus improving the accuracy and sensitivity of the sensor.
Implementation Method 1
at least one heating element and at least one temperature sensor element are applied to a substrate
Implementation Method 2
at least one heating element and at least one temperature sensor element are applied to a substrate
Data Source
Figure 1~3
Figure 4a~5
AI summary
A sensor (1) for determining at least one process variable of a medium (2), said sensor at least comprising: - a metallic substrate (3) which has a recess (5) at least in a first area (4); - a first dielectric layer (6) which is arranged on the metallic substrate (3) at least in the first area (4), wherein the first dielectric layer (6) forms a membrane (7); - at least one heating structure (8) which is arranged on the first dielectric layer (6) formed as a membrane (7) in the first area (4), wherein the heating structure (8) heats the medium (2); - at least one temperature sensor element (9) assigned to the first area, which temperature sensor element is arranged so as to be spaced apart from the heating structure (8) on the first dielectric layer (6) and detects the temperature of the medium (2) heated on the heating structure (8); and - at least one protective layer (10) which covers at least the at least one heating structure (8) and the at least one temperature sensor element (9).