Thermal Flow Sensor Channel Profile Design for Turbulence Reduction
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Solution Overview
Problem
Existing fluid flow measurement apparatuses face limitations in sensitivity at higher flow rates due to turbulences caused by electrical connections and dead volumes, especially with micro-scale flow sensors, which affect measurement accuracy and robustness across varying conditions.
Innovation Solution
A thermal flow sensor apparatus with a semiconductor chip and a unique channel profile design that minimizes turbulences by optimizing the channel's dimensions and arrangement, ensuring the thermal flow sensor is thermally isolated and directly exposed to the fluid, reducing measurement noise while increasing the flow range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If wider channels are designed to increase flow rates, then the maximum flow range is increased, but electrical connections for the flow sensor may affect the flow of the fluid by causing turbulences
Solution Approach 1:
The patent extracts the electrical connections (bond wires) from the channel interior by providing a support structure that positions the flow sensor away from the channel walls. This allows the bond wires to be located outside the channel, eliminating the turbulence they cause while maintaining electrical connectivity to the sensor.
Solution Approach 2:
The patent introduces a support structure as an intermediary element between the flow sensor and the channel. This support structure serves as a mediator that holds the sensor in an optimal position within the channel, ensuring accurate flow measurement while preventing the sensor and its connections from disrupting the fluid flow.
2Productivity
If a micro-scale flow sensor is used in a wide channel, then higher flow rates can be measured, but a dead volume may be generated between the flow sensor and the channel due to alignment accuracy
Solution Approach 1:
The patent extracts the flow sensor from the conventional embedded position within the channel wall and positions it freely within the channel using a support structure. This extraction eliminates the dead volume that arises from alignment inaccuracies when embedding micro-scale sensors in wide channels.
Solution Approach 2:
The patent transitions from a two-dimensional embedding approach (sensor embedded in channel wall) to a three-dimensional positioning approach (sensor positioned freely within channel volume). This dimensional change allows optimal positioning of the sensor away from walls, eliminating dead volume effects.
3Ease of manufacture
If the flow sensor is placed closer to the channel wall for better alignment, then manufacturing is easier, but dead volume is generated affecting measurement
Solution Approach 1:
The patent extracts the flow sensor from the channel wall embedding approach and positions it freely within the channel using a support structure. This eliminates the need for precise alignment with the channel wall while preventing dead volume formation.
Solution Approach 2:
The support structure acts as an intermediary that simplifies manufacturing by providing a standardized mounting position for the sensor, eliminating complex alignment requirements with the channel wall while maintaining measurement accuracy.
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 enhances measurement sensitivity and robustness across a wider flow range by reducing turbulences and noise, maintaining accuracy at both high and low flow rates, and is less prone to clogging.
Implementation Method 1
The thermal flow sensor is capable of measuring the flow of a fluid based on thermal measurements. For example, the thermal flow sensor may comprise a heater and thermosensors arranged at two opposite sides of the heater
Implementation Method 2
The flow of the fluid can be determined subject to a difference between temperatures measured by the respective thermosensors upstream and downstream of the heater while heating
Data Source
Figure 1a~1c
Figure 2~3
Figure 4~6
AI summary
An apparatus for measuring a flow of a fluid (F), comprises a thermal flow sensor (2) with a sensitive area (21), and a channel (1) for guiding the fluid, which channel (1) comprises a measuring section (11) with a profile (A) perpendicular to a direction of the flow of the fluid (F), which profile (A) has a height (H) orthogonal to the flow of the fluid (F) and perpendicular to a plane defined by the sensitive area (21), and a width (W) orthogonal to its height (H). A core (C) of the profile (A) is defined as area of the profile (A) with maximal height (H1). The core (C) has a characteristic width (W1) defined as minimal uniform width (W) the core (C) takes along at least a quarter of its height (H) irrespective of any branches (111) laterally emanating from the core (C) or in view of any neck in the core (C) effecting an intermittent width (W) of the profile (A) different from the characteristic width (W1). The thermal flow sensor (2) is arranged and configured to measure the flow of the fluid (F) in the measuring section (11). The maximal height (H1) of the profile (A) is at least three times larger than the characteristic width (W1).