Thermal Flowmeter Power Compensation via Temperature Gradient
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Solution Overview
Problem
Conventional thermal flowmeters with heaters and temperature sensors external to the pipe fluid passage exhibit reduced responsiveness to flow rate changes, leading to increased measurement errors due to indirect exposure.
Innovation Solution
A thermal flowmeter configuration with first and second thermal resistive elements on the pipe, a control unit to maintain a temperature difference, a power measurement unit, a temperature difference gradient calculation unit, and a power compensation unit to adjust power based on the gradient, enabling improved flow rate calculation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the heater and temperature sensors are disposed on the exterior of the pipe, then corrosion due to the liquid is avoided, but responsiveness to changes in the flow rate is reduced
Solution Approach 1:
The pipe wall acts as an intermediary medium that transmits thermal energy from the externally disposed heater to the fluid while protecting the heater from direct contact and corrosion. The thermal conductivity of the pipe wall enables heat transfer without requiring direct exposure of the heating element to the corrosive fluid environment.
2Reliability
If the heater and temperature sensors are disposed on the exterior of the pipe, then the structure is protected from corrosion, but measurement error increases
Solution Approach 1:
The pipe wall serves as a thermal intermediary that couples the external heater and sensors to the fluid. By optimizing the thermal properties and thickness of the pipe wall, the system achieves both corrosion protection and sufficient thermal coupling for accurate flow rate measurement.
Solution Approach 2:
The system adjusts thermal parameters such as heater power, temperature differential, and pipe wall thermal conductivity to optimize the balance between corrosion protection and measurement accuracy. By controlling the temperature difference across the pipe wall, the system maintains measurement precision while protecting components from corrosion.
3Measurement precision
If power compensation based on temperature difference gradient is implemented, then flow rate measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The control unit continuously monitors the temperature difference between upstream and downstream thermal resistive elements and adjusts the power supplied to the heater accordingly. This feedback mechanism compensates for thermal losses and maintains accurate flow rate measurements by dynamically adjusting heating power based on real-time temperature gradient measurements.
Solution Approach 2:
The patent replaces complex mechanical flow measurement mechanisms with a thermal-based electrical system. By using electrical heaters and temperature sensors with electronic control, the system achieves accurate flow measurement through software-based power compensation algorithms rather than mechanical adjustments or complex hardware systems.
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
Enhances responsiveness to flow rate changes and reduces measurement errors by compensating power based on temperature difference gradients, even when elements are not directly exposed to the fluid.
Implementation Method 1
a control unit (11), a power measurement unit (7), a temperature difference gradient calculation unit (8), a power compensation unit (9), and a flow rate calculation unit (10)... cause the second thermal resistive element to generate heat
Implementation Method 2
The first thermal resistive element (2a) is disposed on the pipe (1) and configured to sense a first temperature of the measurement target fluid... The second thermal resistive element (2b) is disposed on the pipe (1) downstream relative to the first thermal resistive element (2a) and configured to sense a second temperature of the measurement target fluid
Data Source
AI summary
A thermal flowmeter includes: a first thermal resistive element disposed on a pipe and sensing a first temperature of a fluid; a second thermal resistive element disposed on the pipe downstream relative to the first thermal resistive element and sensing a second temperature thereof; a control unit causing the second thermal resistive element to generate heat so that the second temperature is kept higher than the first temperature by a predetermined value; a power measurement unit measuring a power supplied to the second thermal resistive element; a temperature difference gradient calculation unit calculating a gradient of a difference between the second and first temperatures; a power compensation unit compensating the measured power based on the gradient of the difference and a value of the power when no fluid is in the pipe; and a flow rate calculation unit calculating a flow rate of the fluid based on the compensated power.