Parallel Thermal Flow Sensor Layout for Larger Tube Measurement
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Solution Overview
Problem
Existing thermal flow sensors are limited to measuring flow rates in micromachined channels and require recalibration when the medium changes, and there is a need for faster and bidirectional flow measurement in larger tubes.
Innovation Solution
A thermal flow sensor with multiple flow sensing elements arranged parallel to the flow section, allowing for flow rate measurement in larger tubes, capable of measuring flow velocity at different locations and compensating for fluid thermal properties, using a Wheatstone bridge configuration with flow sensing wires and a measurement cavity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If thermal flow sensors are designed for micromachined channels, then they can measure flow rate in small channels, but they cannot measure flow rate in larger tubes
Solution Approach 1:
The sensor is divided into multiple independent flow sensing elements (at least two) arranged in parallel within the flow section. Each sensing element can independently measure flow velocity at its location, allowing the sensor to accurately measure flow rates in larger tubes while maintaining the same basic micromachined channel structure.
2Volume of moving object
If multiple flow sensing elements are arranged in the flow section, then flow rate measurement in larger tubes becomes possible, but device complexity increases
Solution Approach 1:
Multiple flow sensing elements are integrated into a single sensor body with a common flow section, forming a unified structure that measures flow at multiple locations simultaneously. The sensing elements are arranged in parallel and can be read out through a shared readout mechanism, combining the functionality of multiple sensors into one device.
3Ease of manufacture
If thermal flow sensors are used, then they have simple working principle and low fabrication cost, but they require calibration whenever the medium changes
Solution Approach 1:
The patent replaces the traditional thermal conduction-based flow measurement with a direct thermal conductivity measurement approach. By measuring the thermal conductivity of the fluid directly and using this information to compensate for thermal property variations, the sensor achieves medium independence without requiring recalibration when the fluid type changes.
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 flow rate measurement in larger tubes independent of fluid thermal properties, with increased speed and capability for bidirectional flow detection, suitable for applications like medical ventilation.
Implementation Method 1
heating a heating wire configured for being heated with a constant current (DC) or very low frequency alternating current (AC), for heating the portion of the fluid
Implementation Method 2
measuring the voltage of the heating wire during the heating of the portion of the fluid with voltage measurement means connected to the heating wire, wherein the measured voltage is related to a thermal conductivity
Data Source
AI summary
The invention relates to a thermal flow sensor (2) for determining a flow rate of a fluid (1), comprising:a sensor body (11) with a flow section (12), through which fluid flows (3) in a flow direction during use,a flow sensor configuration (13), comprising multiple flow sensing elements (14), such as two or three, arranged at multiple locations in the flow section for measuring the flow velocity at different locations in the flow section,wherein the multiple flow sensing elements (14) are arranged parallel to each other in a plane parallel to the flow section, and wherein single flow sensing elements (14) of the multiple flow sensing elements (14) can be read out.