External Thermal Flow Sensor for Gas Metering
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Solution Overview
Problem
Existing gas meters face challenges in manufacturing simplicity, maintenance complexity, and compliance with stringent fire protection regulations, particularly due to complex and costly electrical feedthroughs and corrosion risks in thermal gas measuring devices.
Innovation Solution
A thermal gas measuring device design featuring a main housing with bypass openings for a thermal flow sensor located outside the main body, reducing the need for complex electrical feedthroughs and allowing easier sensor replacement, with a separate bypass housing that can be made from non-metallic materials to minimize fire protection requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the thermal flow sensor is located inside the gas meter housing, then the measurement function is integrated, but the electrical feedthrough becomes complex and costly
Solution Approach 1:
The thermal flow sensor is extracted from the gas meter housing and mounted externally on the housing wall. This extraction eliminates the need for complex electrical feedthrough arrangements through the housing wall, as the sensor can be connected via simple cable routing. The sensor is positioned in the air space outside the gas-carrying area, allowing straightforward electrical connections while maintaining measurement functionality.
Solution Approach 2:
A bypass channel is introduced as an intermediary element that allows a portion of the gas flow to be diverted to the thermal flow sensor located outside the main housing. The bypass channel connects the gas-carrying area to the external sensor location, enabling the sensor to measure gas parameters without being physically inside the housing. This intermediary solution resolves the contradiction by providing both measurement access and simplified electrical connections.
2Ease of repair
If the sensor element is located in the gas-carrying area, then direct measurement is possible, but maintenance complexity increases
Solution Approach 1:
The thermal flow sensor is extracted from the gas-carrying area and positioned in the air space outside the housing. This allows the sensor to be accessed and replaced without opening the gas meter housing, significantly simplifying maintenance operations. The sensor becomes an externally accessible component that can be serviced independently of the sealed housing structure.
Solution Approach 2:
The gas meter system is segmented into separate functional areas: the gas-carrying area enclosed by the housing and the sensor area in the external air space. This segmentation allows the sensor to be maintained independently without compromising the integrity of the gas meter housing or requiring complex disassembly procedures.
3Reliability
If electrical cables are routed through the housing wall, then power and signals are transmitted, but fire protection requirements increase
Solution Approach 1:
The thermal flow sensor and its electrical connections are extracted from the gas-carrying area to the external air space. This eliminates the need for complex electrical feedthrough arrangements through the fire-rated housing wall. Electrical cables can be routed externally along the housing surface, maintaining fire protection integrity while providing necessary power and signal transmission to the sensor.
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 design simplifies manufacturing and maintenance, reduces corrosion risks, and meets fire protection standards by eliminating the need for expensive electrical feedthroughs and allowing external sensor access, while maintaining accurate measurement of gas parameters like flow rate and calorific value.
Implementation Method 1
a thermal flow sensor (22) for determining at least one characteristic parameter of the combustible gas flowing through the main housing
Implementation Method 2
the gas flowing through the bypass channel passes over the flow sensor
Data Source
Figure 1~2
Figure 3~4
Figure 5~7
AI summary
A gas measuring device for a flammable gas (G), in particular natural gas, has a main housing (10) which defines a gas inlet (12) and a gas outlet (13) for the gas. At least one connection element (14; 15) is arranged on the main housing to connect the gas inlet to a gas inlet line (61) and the gas outlet to a gas outlet line (62). A flow resistance element (31) is arranged inside the housing between the gas inlet and the gas outlet and delimits a main channel for the gas flowing through the main housing. The main housing has a first and second bypass opening (16, 17). A bypass channel (21) runs outside the main housing between the first and second bypass openings. A thermal flow sensor (22) is arranged outside the main housing adjacent to the bypass channel.