Ultrasonic Flowmeter Flat Sensor Plate Temperature Error
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Solution Overview
Problem
Conventional ultrasonic flowmeters face temperature measurement errors due to heat transfer from metallic cylindrical thermistors, especially when the ambient temperature differs significantly from the fluid temperature, and this issue is exacerbated by high flow velocities or when measuring gases or low-flow fluids.
Innovation Solution
An ultrasonic flowmeter design featuring a flat, flexible sensor plate with a temperature sensor integrated into the flow path, reducing ambient temperature influence and enhancing measurement accuracy by minimizing heat transfer and flow resistance, while also incorporating a pressure sensor for improved versatility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a cylindrical thermistor is inserted into the flow path to measure temperature, then temperature measurement is enabled, but the metallic cylindrical portion causes heat transfer from the ambient temperature of the flow path body, leading to measurement errors
Solution Approach 1:
The patent replaces the rigid cylindrical thermistor with a flat sensor plate that has flexibility and thin film characteristics. This sensor plate is disposed to project into the flow path cross-section, allowing it to conform to the flow path geometry while minimizing thermal mass and heat transfer from the flow path body walls, thereby reducing ambient temperature influence on measurements.
Solution Approach 2:
The patent transitions from a one-dimensional cylindrical thermistor to a two-dimensional flat sensor plate configuration. This dimensional change allows the temperature sensor to be positioned at multiple locations across the flow path cross-section simultaneously, improving measurement accuracy while reducing the influence of any single point's ambient temperature.
2Object-affected harmful factors
If the diameter of the cylindrical portion is reduced to reduce wall surface influence, then ambient temperature influence decreases when heat transfer is high, but temperature measurement error may occur when heat transfer is not large (gas flow or low velocity)
Solution Approach 1:
The flat sensor plate design provides a large surface area relative to its thickness, enabling effective thermal coupling with the fluid even when heat transfer is low. The thin film structure minimizes thermal mass while the extended surface area ensures adequate heat exchange with the flowing fluid, solving the problem of insufficient heat transfer in gas or low-velocity flows.
Solution Approach 2:
The sensor plate design is universally applicable to different fluid types (liquid and gas) and flow conditions (high and low velocity). By providing a large surface area with minimal thermal mass, it effectively couples with fluids across various heat transfer regimes, eliminating the need to adjust diameter based on flow conditions.
3Reliability
If a cylindrical thermistor is used with hermetic sealing, then the temperature sensor is protected, but the metallic structure and sealing components increase device complexity and may introduce additional heat transfer paths
Solution Approach 1:
The flat sensor plate can be directly mounted to the flow path body using simplified sealing methods such as gaskets or adhesive bonding, eliminating the need for complex hermetic sealing of cylindrical structures. The flexible nature of the thin plate allows it to conform to the mounting surface, providing reliable sealing with minimal components.
Solution Approach 2:
The patent extracts the temperature sensing function from the complex cylindrical thermistor assembly and implements it in a simplified flat plate configuration. This separation allows the sensor to be directly integrated into the flow path structure without requiring separate hermetic sealing systems, reducing overall device complexity.
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 design significantly reduces temperature measurement errors, achieves high accuracy for fluid temperature and flow rate measurements, and offers versatility and ease of assembly with a compact, cost-effective configuration.
Implementation Method 1
ultrasonic waves are propagated to measurement flow path 106 to measure a flow velocity and a flow rate
Implementation Method 2
calculates a flow rate of the fluid to be measured from a propagation time of ultrasonic waves between the pair of ultrasonic transducers
Implementation Method 3
a temperature sensor for detecting a temperature of the fluid to be measured is disposed
Data Source
AI summary
An ultrasonic flowmeter includes: a flow path body having a flow path through which a fluid to be measured flows; a pair of ultrasonic transducers disposed in the flow path body; a substrate fixed to the flow path body; a sensor plate on which a temperature sensor for detecting a temperature of the fluid to be measured is disposed, the sensor plate being flat; and an arithmetic unit that calculates a flow rate of the fluid to be measured from a propagation time of ultrasonic waves between the pair of ultrasonic transducers and the temperature detected by the temperature sensor. The sensor plate is configured to project from the substrate and to project into a flow path cross-section of the flow path from a sensor hole provided in the flow path body at a time of fixing the substrate to the flow path body.