Thermal Flowmeter Probe Core Brazing Method
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Solution Overview
Problem
Existing thermal flow meter probes experience fluctuations in heat transfer and are prone to aging, leading to measurement errors that require recalibration, affecting the consistency and accuracy of mass flow measurements.
Innovation Solution
A method involving a probe core made of a brazing alloy with a core element inserted into a probe sleeve, where the alloy is melted and cooled to form an intermetallic compound layer, and a thermocouple is attached using a solder or sinter layer, with a second sleeve attached leak-tight to ensure stable heat transfer and temperature sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a filling material is used to embed the thermocouple in the probe sleeve, then the thermocouple is protected and positioned, but heat transfer resistance increases and fluctuates between different probes
Solution Approach 1:
The invention removes the filling material from the probe structure entirely. Instead of embedding the thermocouple in filling material, the thermocouple is directly attached to the probe core surface, eliminating the intermediate material that causes heat transfer resistance and variability between probes.
Solution Approach 2:
The invention uses a composite structure consisting of the probe sleeve, probe core, and thermocouple attached directly to the probe core. This composite design eliminates the need for filling material while maintaining structural integrity and thermal contact.
2Ease of manufacture
If filling material is used in the probe, then the thermocouple is secured, but the probe becomes susceptible to aging and requires recalibration
Solution Approach 1:
The invention extracts and removes the filling material from the probe structure. By directly attaching the thermocouple to the probe core without filling material, the probe eliminates the aging-related degradation that occurs in filling materials, thereby extending its stable operational lifetime.
3Reliability
If a thermocouple is embedded in filling material, then the thermocouple is protected, but heat transfer resistance between the probe and medium increases
Solution Approach 1:
The invention removes the filling material that acts as a thermal barrier. The thermocouple is directly attached to the probe core surface, creating a direct thermal pathway to the medium and eliminating the heat transfer resistance introduced by filling material.
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 provides improved stability and long-term behavior of the probes, maintaining high sensitivity and accuracy by ensuring uniform heat distribution and temperature application, reducing the need for recalibration due to aging issues.
Implementation Method 1
melting the braze
Implementation Method 2
cooling the hard solder to a temperature lower than the solidification temperature
Implementation Method 3
a thermocouple is attached to a contact surface of the core member or the solidified braze
Implementation Method 4
the thermocouple is attached to the contact surface by means of a layer of solder or sinter
Data Source
Figure 1
Figure 2a~2c
Figure 3
AI summary
The invention relates to a method for producing a probe (10) of a thermal flow meter for measuring the mass flow rate of a medium in a measuring tube, said method having the following steps: introducing a probe core comprising a brazing solder and a core element into a first probe casing, the first probe casing having an open first end and a closed second end facing away from the first end; melting the brazing solder; fixing the core element by quenching the brazing solder to a temperature below the solidification temperature; attaching a thermoelement to a contact surface of the core element or the solidified brazing solder. The invention also relates to a probe obtained according to the production method and to a flow meter comprising at least one probe according to the invention.