Gas Flux Measurement Correction for T-P Effects
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Solution Overview
Problem
Existing gas analyzers face challenges in accurately measuring gas flux due to temperature-pressure (T-P) effects, which are difficult to correct for in fast measurements without precise and integrated temperature and water content measurements across the sampling volume, especially in remote locations where fast temperature changes are common.
Innovation Solution
The solution involves correcting gas flux for T-P effects using conventional fast measurements of air temperature and water content taken away from the gas sampling path, allowing for reliable correction over integration intervals of 10 minutes to 4 hours, simplifying instrumental requirements and enabling the design of low-power gas analyzers with short intake tubes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional gas analyzers use long intake tubes and powerful pumps to maintain sample gas flow, then measurement reliability is improved, but power consumption increases and device portability worsens
Solution Approach 1:
The patent removes the pump component entirely from the system, transitioning from a closed-path to an open-path measurement approach. This extraction eliminates the need for mechanical pumping while maintaining measurement capability through direct ambient air sampling along the laser beam path.
Solution Approach 2:
The patent divides the measurement system into separate functional components: the laser-based gas density measurement occurs along an open optical path, while temperature and water content measurements are performed by separate sensors positioned at different locations, with data integrated through computational correction.
2Speed
If fast measurements of gas density are performed to capture rapid temperature changes, then measurement speed is improved, but correction for T-P effects becomes more difficult
Solution Approach 1:
The patent introduces computational algorithms as an intermediary that processes data from multiple independent measurements (gas density from laser absorption, temperature from thermocouples, water content from hygrometers) and applies physics-based corrections for thermal expansion and water dilution effects to derive accurate gas flux.
Solution Approach 2:
The patent transforms the measurement approach by continuously monitoring multiple parameters (gas density, temperature, water content) simultaneously and using their temporal relationships to correct for T-P effects, rather than attempting to measure a single corrected parameter directly.
3Measurement precision
If accurate and precise fast measurements of gas temperature and water content are taken integrated over the sampling volume, then correction accuracy for T-P effects is improved, but device complexity and power consumption increase
Solution Approach 1:
The patent employs universal sensing principles where standard temperature sensors (thermocouples) and humidity sensors (hygrometers) positioned near the measurement path provide sufficient data for T-P correction, eliminating the need for specialized integrated measurement devices.
4Stability of the object's composition
If closed-path sensors with long intake tubes are used to protect the sampling path, then measurement stability is improved, but response time to fast temperature changes worsens
Solution Approach 1:
The patent inverts the conventional approach by placing sensors in the ambient environment rather than protecting samples through long intake tubes. The open optical path and nearby temperature/humidity sensors directly experience ambient conditions, providing immediate response to environmental changes.
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 approach allows for accurate gas flux measurements with reduced power consumption, enabling the use of low-power open-path and closed-path sensors that can be deployed in remote locations, suitable for research and monitoring applications, such as Eddy Covariance and marine methods, with similar accuracy to conventional systems.
Implementation Method 1
a laser is used to measure a density of the target gas by an absorption of the laser by the target gas
Implementation Method 2
the measured signal is temperature and pressure dependent due to the combined effects of Boltzmann population distribution of rotational levels and Doppler broadening
Implementation Method 3
temperature-dependent pressure broadening of individual lines
Implementation Method 4
the measured gas density itself changes with temperature and water content due to thermal expansion and water dilution of the gas per the Ideal Gas Law
Implementation Method 5
the measured gas density itself changes with temperature and water content due to thermal expansion and water dilution of the gas per the Ideal Gas Law
Data Source
Figure 1~2
Figure 3~4
Figure 5A
AI summary
Disclosed embodiments of the present invention provide means to obtain correct gas density and flux measurements using (i) gas analyzer (open-path, or closed-path gas analyzers with short intake tube, for example 1 m long, or any combination of the two); (ii) fast temperature or sensible heat flux measurement device (such as, fine-wire thermocouple, sonic anemometer, or any other device providing fast accurate gas temperature measurements); (iii) fast air water content or latent heat flux measurement device (such as, hygrometer, NDIR analyzer, any other device providing fast accurate gas water content measurements); (iv) vertical wind or sampling device (such as sonic anemometer, scintillometer, or fast solenoid valve, etc.) and (v) algorithms in accordance with the present invention to compute the corrected gas flux, compensated for T-P effects. In case when water factor in T-P effects is negligible, the fast air water content or latent heat flux measurement device can be excluded.