Thermal Gas Flow Detector Using Intermediary Sensing Tube
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Solution Overview
Problem
Existing methods for monitoring differential gas pressure and low gas flow rates are either too complex, expensive, or inaccurate, and direct sensors often require invasive placement, making them costly and difficult to maintain.
Innovation Solution
A combination of thermo-anemometry and classical Pitot tubes is used, with a sensing tube equipped with an air temperature sensor and a thermally coupled heater, connected to an electronic servo control loop, to measure air mass flow rate and differential pressure, allowing for continuous monitoring of gas flow and pressure changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If indirect pressure measurement method is used, then device complexity is reduced, but measurement precision deteriorates for low flow rates
Solution Approach 1:
The patent introduces a sensing tube with a heater as an intermediary element between the gas flow and the temperature sensors. The heater transfers thermal energy to the gas flow, and the temperature sensors measure the thermal effects, enabling indirect measurement of flow rate and pressure with high precision without direct sensor placement in the flow path.
Solution Approach 2:
The patent replaces direct mechanical pressure sensing with a thermal-based measurement system. By using temperature sensors to detect thermal effects caused by gas flow interaction with the heated sensing tube, the system achieves precise measurements without requiring complex mechanical pressure transducers.
2Measurement precision
If direct flow sensors are used, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The sensing tube with heater acts as a mediator that converts gas flow parameters into thermal effects that can be measured by simple temperature sensors, avoiding the need for complex direct flow sensors while maintaining measurement precision.
Solution Approach 2:
The patent changes the measurement parameter from direct pressure or flow measurement to temperature measurement. By heating the sensing tube and measuring temperature changes caused by gas flow, the system achieves precise measurements using simpler temperature sensing technology.
3Measurement precision
If direct flow sensors are used, then measurement precision is improved, but ease of operation deteriorates due to invasive placement requirements
Solution Approach 1:
The sensing tube serves as an intermediary that can be placed in the flow path without requiring direct sensor insertion into the gas stream. The temperature sensors remain protected outside the flow path while the heated tube interacts with the gas, simplifying installation and maintenance.
4Measurement precision
If sensitive pressure detectors are used, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent substitutes mechanical pressure detection systems with a thermal-based measurement system. By measuring temperature changes in the sensing tube caused by gas flow rather than directly measuring pressure, the system achieves high precision using simpler temperature sensor technology.
Solution Approach 2:
The measurement parameter is changed from pressure to temperature. The gas flow's effect on the heated sensing tube is measured through temperature changes rather than pressure changes, enabling precise measurements with less complex sensing technology.
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
This solution provides accurate, inexpensive, and simple monitoring of gas flow rates and pressure changes over a broad temperature range, enabling effective detection of air filter clogging and small pressure variations, suitable for HVAC systems, security systems, and fuel burners.
Implementation Method 1
a sensing tube having an opening and two sensors where one is the air temperature sensor and the other is a similar temperature sensor being thermally coupled to a heater
Data Source
AI summary
A detector for monitoring the low levels of differential pressures and the rate of mass flow rate of gas (air, e.g.) in a duct. The sensor's temperature is maintained at a constant gradient above temperature of the flowing gas, typically 4-7° C. higher. The detector consists of two thermally decoupled sensors—one is the air temperature sensor and the other is a temperature sensor coupled to a heater. The sensors are connected to an electronic servo circuit that controls electric power supplied to the heater. The sensors are positioned outside of the air duct and coupled to the duct via a relatively thin sensing tube protruding inside the duct. The end of the tube has an opening facing downstream of the gas flow, thus being exposed to a static gas pressure. The detector can be employed in fuel burners of the HVAC systems, internal combustion engines, medical equipment to control flow of anesthetic gases, in the security systems to monitor minute changes in air pressure resulted from opening and closing of doors and windows in a protected facility.