Droplet Detection on Heated Thermal Flow Sensors
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Solution Overview
Problem
Conventional thermal flowmeters face challenges in accurately measuring mass flow due to droplet precipitation on heated temperature sensors, which can lead to incorrect flow rate determination and potential damage to downstream mechanical components, especially in two-phase flows like biogas with high humidity.
Innovation Solution
A method to detect droplet precipitation on heated temperature sensors by analyzing the heat transfer measurements, specifically identifying the largest heat transfer value and checking for periodicities within predetermined time windows, and signaling alarm or correcting flow signals as necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If thermal flow meters are used in high-humidity gaseous environments, then flow rate measurement is enabled, but droplet precipitation on heated temperature sensors occurs leading to incorrect measurements
Solution Approach 1:
The patent applies preliminary action by detecting droplet precipitation before it significantly affects the measurement. The evaluation unit continuously monitors heat transfer values and identifies droplet formation early by comparing current heat transfer values with reference values, allowing the system to warn operators or correct measurements before accuracy is compromised
Solution Approach 2:
The patent implements feedback by using the heat transfer measurement to detect droplet precipitation and feed this information back to the evaluation unit. The system compares the measured heat transfer value with reference values and provides feedback about droplet presence, enabling continuous monitoring and correction of measurement accuracy
2Productivity
If droplet precipitation is not detected, then the flow meter operates continuously, but incorrect flow rate determination occurs and downstream mechanical components may be damaged
Solution Approach 1:
The patent converts the harmful effect of droplet precipitation into a beneficial detection opportunity. By measuring the heat transfer change caused by droplets on the heated sensor, the system transforms a potentially damaging condition into a detectable signal that triggers warnings or corrections, preventing downstream mechanical damage
Solution Approach 2:
The patent uses the heated temperature sensor as an intermediary to detect droplet precipitation. The sensor serves dual purposes: measuring temperature for flow rate calculation and detecting droplet presence through heat transfer changes, thereby preventing harmful effects before they reach downstream mechanical components
3Measurement precision
If conventional heat transfer measurement is used, then flow rate can be determined, but droplet precipitation cannot be distinguished from normal flow conditions
Solution Approach 1:
The patent applies segmentation by separating the measurement evaluation into distinct components: a normal flow rate determination based on heat transfer and a droplet detection evaluation based on comparing heat transfer values with reference values. This segmentation allows the system to simultaneously perform both functions without interference
Solution Approach 2:
The patent uses parameter changes by monitoring changes in heat transfer values that indicate droplet precipitation. The evaluation unit detects droplets by identifying specific patterns in heat transfer parameter changes that differ from normal flow conditions, enabling distinction between droplet presence and normal operation
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
Effectively warns operators of two-phase flows, ensuring accurate flow rate measurement and preventing mechanical damage by reliably detecting droplet formation, even in high-humidity gaseous environments, thereby maintaining the integrity of thermal flowmeters.
Implementation Method 1
Heat transfer into and/or out of the resistance element therefore occurs via two opposing surfaces... the cooling of the heated temperature sensor depends significantly on the mass flow rate of the flowing medium. Since the medium is colder than the heated temperature sensor, heat is carried away from the sensor by the flowing medium.
Implementation Method 2
This heating element is either an additional resistance heater or the temperature sensor itself is a resistance element, such as an RTD (Resistance Temperature Device) sensor, which is heated by the conversion of electrical power
Data Source
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AI summary
Method for the recognition of a droplet deposition on a heated temperature sensor, in particular a thermal flow measuring device for the measurement of the flow of a fluid, characterised by the following process steps: determination of the largest value of a measurement for a thermal transfer from the heated temperature sensor to the fluid in a first time window of a specified length; checking of the values of the measurement for the measurement for the thermal transfer in the first time window for the presence of a value of the measurement for the thermal transfer in each case that are smaller than the difference from the largest value and the specified (Delta1); use of the result of the check for the recognition of the droplet deposition.