Thin-Film Thermal Flowmeter Sensor with Isolated Elements
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Solution Overview
Problem
Conventional thermal flowmeters face challenges in quickly detecting temperature changes and operating efficiently, especially in applications involving liquids, due to high heat transfer and heating power requirements.
Innovation Solution
A thin-film sensor with a gap isolating two sensor elements, allowing for rapid temperature difference determination, combined with a low-energy operation mode using an energy storage element and control unit for pulsed power supply to the heatable sensor element, optimizing energy balance and reducing energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If thermal flowmeters use conventional sensor design without isolation, then the structure is simpler, but the response time is slower due to thermal coupling between sensor elements
Solution Approach 1:
The sensor is divided into two isolated sensor elements (heating element and measuring element) separated by a gap in the thin-film substrate. This segmentation prevents thermal coupling between the elements, allowing the heating element to transfer heat to the medium without directly heating the measuring element, thereby enabling faster response time for temperature difference detection.
Solution Approach 2:
The thin-film substrate acts as an intermediary that conducts heat from the heating element to the medium while the gap prevents direct thermal conduction to the measuring element. The medium itself serves as the heat transfer intermediary, carrying thermal energy from the heating element to the measuring element through the fluid flow, enabling rapid temperature difference determination.
2Reliability
If thermal flowmeters operate with continuous heating, then the temperature measurement is stable, but the energy consumption is high
Solution Approach 1:
The heating element is operated in periodic pulses rather than continuous heating. During heating pulses, the heating element transfers heat to the medium, and during interval pauses, the heating is stopped while the measuring element continues to detect temperature differences. This periodic operation maintains sufficient measurement stability while significantly reducing average energy consumption compared to continuous heating.
Solution Approach 2:
The heating element performs preliminary heating action during short pulses to create a temperature difference in the medium, which is then detected by the measuring element during the subsequent pause period. This preliminary heating action is sufficient to establish measurable temperature gradients without requiring continuous energy input, optimizing the balance between measurement reliability and energy efficiency.
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 quick response times and low-energy operation of the thermal flowmeter, allowing for efficient mass flow monitoring with reduced energy consumption and extended measuring times.
Implementation Method 1
The application of the measuring principle is particularly challenging in water and other liquids, such as oil for instance, as the transfer of heat and the necessary heating power are considerably higher here compared to gases.
Implementation Method 2
at least a second of the two sensor elements is designed to determine the temperature of the medium
Implementation Method 3
the thin-film sensor has a gap that isolates the two sensor elements from one another. As a result of the isolation, here both electrical isolation and, in particular, thermal insulation of the two sensor elements, a temperature difference between the two sensor elements arises more quickly
Data Source
AI summary
A thin-film sensor for a thermal flowmeter with at least a first substrate layer made of electrically non-conductive material, a second layer made of electrically conductive material and a cover layer to protect the resistance layer against abrasion, wherein the second layer is designed as two sensor elements, wherein at least a first of the two sensor elements is designed to introduce a heat quantity into a medium, and at least a second of the two sensor elements is designed to determine the ambient temperature, and the thin-film sensor has a gap that isolates the two sensor elements from one another.