Rhombus Thermal Flowmeter Probe Arrangement for Direction Detection
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Solution Overview
Problem
Existing thermal flowmeters face challenges in accurately determining the flow direction of a medium at low to medium flow velocities, resulting in high uncertainties.
Innovation Solution
A thermal flow measuring device with a sensor arrangement featuring four probes, where the probes are strategically positioned to heat and measure the medium's temperature, with a fourth probe designed to hinder partial flow between the first and third probes, achieving symmetry in flow resistance for both flow directions, and allowing for improved flow direction detection through temperature difference analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a flow resistor is used to create direction-dependent flow toward a heatable probe, then the direction of medium flow can be indicated, but at low to medium flow velocities the indication is subject to high uncertainty
Solution Approach 1:
The sensor is divided into four separate probes arranged in a rhombus pattern, with each probe independently configured to heat or measure temperature. This segmentation allows for multiple measurement configurations and improves flow direction detection by comparing temperature differences across different probe pairs, thereby reducing uncertainty at low to medium velocities.
Solution Approach 2:
The fourth probe is designed with asymmetric dimensions (second width greater than first width by factor of at least 1.1) and its geometric center of gravity is offset in the direction of the second probe. This asymmetry creates different flow resistance characteristics for flow moving in opposite directions, enabling reliable flow direction indication even at low to medium velocities where symmetric designs fail.
2Measurement precision
If the probe active body of the fourth probe has asymmetric dimensions with offset center of gravity, then flow direction detection is improved, but probe arrangement complexity increases
Solution Approach 1:
The fourth probe is designed with asymmetric dimensions (second width greater than first width by factor of at least 1.1) and its geometric center of gravity is offset in the direction of the second probe. This asymmetry creates different flow resistance characteristics for flow moving in opposite directions, enabling reliable flow direction indication even at low to medium velocities where symmetric designs fail.
Solution Approach 2:
All four probes share a common sensor base body and are arranged in a rhombus pattern with shared geometric relationships. The first and third probes are positioned symmetrically with respect to the second diagonal, as are the second and fourth probes. This merging of common structural elements reduces overall device complexity despite the asymmetric design of individual probes.
3Measurement precision
If heat flow from the third probe to the first probe is prevented, then flow measurement accuracy is improved, but probe configuration complexity increases
Solution Approach 1:
The fourth probe is designed with asymmetric dimensions (second width greater than first width by factor of at least 1.1) and its geometric center of gravity is offset in the direction of the second probe. This asymmetry creates different flow resistance characteristics for flow moving in opposite directions, enabling reliable flow direction indication even at low to medium velocities where symmetric designs fail.
Solution Approach 2:
The fourth probe acts as an intermediary element that impedes the direct heat flow path from the third probe to the first probe. By positioning the fourth probe to obstruct this specific heat transfer path while maintaining overall probe symmetry, the design prevents parasitic heat conduction that would otherwise degrade flow measurement accuracy without requiring complex thermal isolation structures.
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 reliable flow direction detection over a wide speed range, particularly at high flow speeds greater than 70 m/s, with enhanced measurement accuracy and reduced flow resistance, effectively addressing the uncertainty issues in existing technologies.
Implementation Method 1
the probes are configured to heat the medium, determine its temperature, or influence a flow of the medium in the measuring tube
Implementation Method 2
the fourth probe is designed to impede a partial flow of the medium between the first probe and the third probe
Data Source
Figure 1
Figure 2a~2b
Figure 3
AI summary
Thermal flowmeter (10) for measuring the mass flow rate of a medium in a measuring tube, comprising: a measuring tube (11) having a measuring tube wall (11.1); a sensor (12) having four probes (12.2), which probes project into the measuring tube starting from a main sensor body (12.1), the probes being designed to heat the medium, to determine the temperature of the latter or to influence a flow of the medium in the measuring tube; an electronic measuring/operating circuit (13) which is designed to operate at least three probes and to create and provide flow measurement values by operating said probes, each probe having a main probe body (G) and an active probe body (W), and the active probe body being designed to heat the medium, to determine the temperature of the medium and/or to influence a flow of the medium in the measuring tube, characterized in that the main probe bodies span a rhombus (R) on a surface of the main sensor body and the rhombus is defined by centroid points of cross-sections of the main probe bodies.