Quantitative infrared absorption imaging of vapor concentration fields during evaporation
Abstract
Quantitative full-field measurements of vapor concentration remain challenging near receding liquid-gas interfaces. We develop and quantitatively assess an infrared absorption imaging method for measuring vapor mole-fraction fields during evaporation. Broadband mid-infrared attenuation is converted into mole fraction using a spectrally weighted absorption coefficient. A vertical Hele-Shaw cell provides a controlled, nearly one-dimensional evaporation benchmark, with calibrated object-plane sampling of 30.5 μm/pixel. Small transverse concentration variations in the central measurement region justify reducing the two-dimensional fields to axial profiles. Five profiles spanning different retained gas-phase interval lengths and three hydrocarbon liquids are compared with Stefan predictions using only measured interval lengths and endpoint concentrations, without fitting interior concentration data. At the higher vapor loading of n-pentane, the measurements resolve the nonlinear Stefan concentration profile and distinguish it from the linear diffusion limit. At the lower vapor loadings of n-hexane and n-heptane, the profiles progressively approach that dilute limit. The profiles agree with Stefan predictions, with normalized root-mean-square deviations of 0.0055-0.0185, and collapse onto the predicted identity relation after the logarithmic Stefan transformation. These results demonstrate quantitative recovery of both the magnitude and spatial structure of vapor concentration fields under the tested conditions. The method provides a full-field, tracer-free diagnostic for investigating evaporating flows in geometries and regimes where analytical concentration fields are unavailable.
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BibTeX
@misc{song2026quantitative,
title = {{Quantitative infrared absorption imaging of vapor concentration fields during evaporation}},
author = {Zihao Song and Weitian Wang and Chao Sun and Xing Chao},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2611.06467},
eprint = {2611.06467},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2611.06467},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Quantitative infrared absorption imaging of vapor concentration fields during evaporation
AU - Zihao Song
AU - Weitian Wang
AU - Chao Sun
AU - Xing Chao
PY - 2026
DA - 2026/11/04
PB - arXiv
DO - 10.48550/arxiv.2611.06467
UR - https://arxiv.org/abs/2611.06467
AB - Quantitative full-field measurements of vapor concentration remain challenging near receding liquid-gas interfaces. We develop and quantitatively assess an infrared absorption imaging method for measuring vapor mole-fraction fields during evaporation. Broadband mid-infrared attenuation is converted into mole fraction using a spectrally weighted absorption coefficient. A vertical Hele-Shaw cell provides a controlled, nearly one-dimensional evaporation benchmark, with calibrated object-plane sampling of 30.5 μm/pixel. Small transverse concentration variations in the central measurement region justify reducing the two-dimensional fields to axial profiles. Five profiles spanning different retained gas-phase interval lengths and three hydrocarbon liquids are compared with Stefan predictions using only measured interval lengths and endpoint concentrations, without fitting interior concentration data. At the higher vapor loading of n-pentane, the measurements resolve the nonlinear Stefan concentration profile and distinguish it from the linear diffusion limit. At the lower vapor loadings of n-hexane and n-heptane, the profiles progressively approach that dilute limit. The profiles agree with Stefan predictions, with normalized root-mean-square deviations of 0.0055-0.0185, and collapse onto the predicted identity relation after the logarithmic Stefan transformation. These results demonstrate quantitative recovery of both the magnitude and spatial structure of vapor concentration fields under the tested conditions. The method provides a full-field, tracer-free diagnostic for investigating evaporating flows in geometries and regimes where analytical concentration fields are unavailable.
ER -