Abstract
A prediction method of internal temperatures distributed axisymmetrically in an aqueous solution with a thickness from sub-mm to a few mm is presented. This method consists of a near-infrared (NIR) absorption imaging and an inverse Abel transform. In the NIR absorption imaging, absorbance images at the wavelength of 1412 nm, the most temperature-sensitive wavelength in the v_1 + v_3 absorption band of water, are obtained by using a narrow-bandpass filter and an NIR camera. In the case that the internal temperature possesses an axisymmetric distribution, it can be predicted by Abel inversion of the measured absorbance profile. In this study the absorbance profiles are approximated by multi-Gaussian functions because their inverse transform can be calculated analytically. Cross-sectional temperature distributions around a thin hot wire in 1.5 mm thick water are shown.
