Four-Probe Thermal Flowmeter Layout for Low-Velocity Direction Sensing
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Solution Overview
Problem
Existing thermal flow meters face high uncertainties in determining the flow direction at low to medium flow velocities.
Innovation Solution
A thermal flow meter with a sensor comprising four probes arranged in a rhombus configuration, where two probes heat the medium and two probes measure temperature, allowing for reliable flow direction detection by utilizing power coefficients derived from probe interactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional thermal flow meters with heating probes are used, then mass flow rate can be measured, but flow direction determination becomes highly uncertain at low to medium flow velocities
Solution Approach 1:
The sensor is divided into four separate probes arranged in a rhombus configuration, with each probe having a specific function (two for heating, two for temperature measurement). This segmentation allows each probe to specialize in a particular measurement aspect, improving overall measurement precision and reliability at low flow velocities by isolating functional responsibilities.
Solution Approach 2:
The probes are arranged in an asymmetric rhombus configuration rather than a symmetric pattern, with specific probes positioned to create asymmetric heating patterns relative to the flow direction. This asymmetry enables the system to detect flow direction by measuring temperature differences between probes, achieving reliable direction detection even at low flow velocities where symmetric arrangements fail.
2Adaptability or versatility
If a flow resistance is added to create direction-dependent flow towards a heated probe, then flow direction can be determined, but measurement uncertainty remains high at low flow velocities
Solution Approach 1:
The thermal flow meter performs multiple functions simultaneously: it measures mass flow rate, determines flow direction, and operates effectively across a wide range of flow velocities including low velocities. The four-probe rhombus configuration enables the system to universally handle both flow rate and flow direction measurements without requiring separate mechanisms, achieving high precision in both functions.
Solution Approach 2:
The patent uses temperature distribution in the medium as an intermediary to infer flow direction. Instead of directly measuring flow direction, the heated probes create temperature fields that are distorted by the flowing medium, and the temperature measurement probes detect these distortions. This indirect measurement approach through temperature as an intermediary enables accurate flow direction detection at low velocities.
3Measurement precision
If multiple probes are used for thermal flow measurement, then measurement capability is enhanced, but device complexity increases
Solution Approach 1:
The patent combines multiple measurement functions into a single integrated sensor assembly. The four probes are arranged in a compact rhombus configuration on one side of the measuring tube, merging flow rate measurement and flow direction detection into one unified structure. This consolidation enhances measurement precision while minimizing the increase in device complexity by integrating rather than separating functional elements.
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
Enables accurate and stable flow direction detection even at low flow velocities, ensuring consistent measurement performance.
Implementation Method 1
the probe active element is configured to heat the medium
Implementation Method 2
configured to heat the medium, determine its temperature
Data Source
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AI summary
The thermal flowmeter according to the invention comprises the following: a measuring tube; a sensor comprising four probes, which are designed to heat the medium, determine the temperature thereof, or influence the flow of the medium in the measuring tube; and an electronic measuring/operating circuit, wherein the active bodies of the probes are designed to heat the medium, determined the temperature of the medium, and/or influence the flow of the medium in the measuring tube, and the main parts of the probes define a rhombus on the surface of the sensor main part. A first diagonal of the rhombus is parallel to the measuring tube axis, and a second diagonal lies in the measuring tube cross-section. A first probe and a second probe are designed to heat the medium, and at least a third probe is designed to determine the temperature of the medium. The first probe and the second probe are arranged on the first diagonal, and the at least one third probe is arranged on the second diagonal.