Humidity Sensor Filter Assembly with Purge Gas Ejection
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Solution Overview
Problem
Existing humidity sensing systems fail to provide continuous, precise, and reliable measurements in industrial gas streams containing particulate matter with cohesive or adhesive properties, particularly at temperatures approaching the adiabatic saturation temperature, due to issues like condensation, agglomeration, and adhesion of solids on the sensor.
Innovation Solution
A humidity sensing system is designed with a filtration apparatus that automatically separates solid particulate matter from the gas stream, using a cylindrical barrel housing the humidity sensor and filter assembly, where purge gas is used to reverse flow through the filter and eject accumulated matter, ensuring accurate and reliable measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a humidity sensor is placed directly in a particulate-laden gas stream, then continuous humidity measurement is enabled, but particulate matter accumulates on the sensor causing signal interference and measurement failure
Solution Approach 1:
The system divides the measurement function into two separate components: a filter assembly that separates particulate matter from the gas stream, and a humidity sensor that measures only the filtered gas. This segmentation prevents particles from reaching the sensor while maintaining continuous measurement capability.
Solution Approach 2:
A filter assembly is introduced as an intermediary component between the particulate-laden gas stream and the humidity sensor. The filter acts as a mediator that removes harmful particles while allowing the gas to pass through to the sensor, preventing accumulation and signal interference.
2Reliability
If a filter assembly is added to protect the humidity sensor, then measurement reliability is improved, but device complexity increases
Solution Approach 1:
The filter assembly and humidity sensor are merged into a single integrated housing structure. The filter is positioned within the same enclosure as the sensor, creating a compact unit that protects the sensor while maintaining simplicity in overall system architecture.
Solution Approach 2:
The filter assembly serves multiple functions: it removes particulate matter from the gas stream, protects the humidity sensor from particle accumulation, and maintains continuous gas flow for measurement. This multi-functionality reduces the need for additional protective components.
3Reliability
If purge gas is used to reverse flow through the filter, then particulate removal efficiency is improved, but energy consumption increases
Solution Approach 1:
Instead of continuous purge gas flow, the system uses periodic reverse flow pulses to remove accumulated particulate matter from the filter. This periodic action maintains measurement reliability while significantly reducing energy consumption compared to continuous purging.
Solution Approach 2:
The system discards accumulated particulate matter from the filter using periodic reverse flow, then returns to normal measurement mode. This cyclic discarding process maintains filter effectiveness without requiring continuous energy input for particle removal.
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 system enables continuous, precise, and cost-effective humidity data collection in particulate-laden gas streams by effectively removing particulate matter from the sensor area, preventing interference and maintaining signal continuity and precision.
Implementation Method 1
a protective filter assembly that houses a humidity sensor
Implementation Method 2
The conditioning chambers cause the purge gas temperature and humidity to approach equilibrium with the slipstream flue gas temperature
Implementation Method 3
a spiral helix may be used to increase heat conduction and contact surface area of the purge gas flow through the conditioning chambers
Implementation Method 4
purge gas can pass into the filter reversing the flow of gas through the filter to clean its outside surface of any residual accumulated matter
Data Source
AI summary
A humidity sensor and filter assembly are housed within a cylindrical barrel that is positioned in a process gas stream such as combustion flue gas. A portion of sample flue gas is conducted through the barrel and the filter assembly past the sensor located inside the filter so that accurate humidity measurements can be taken. Unwanted flue gas particulate matter accumulated on the outside surface of the filter is ejected by pulsed purge gas admitted into the filter to reverse the flow through the filter. In one embodiment a heat exchange chamber preheats the purge gas. In another embodiment the pulsed purge is supplied by a reciprocal piston contiguous with the internal volume of the filter that reverses the flow through the filter using the process gas.