Abstract
This paper introduces a novel method for imaging the temperature fields in water with a small heated sphere. This method is based on the temperature dependence of the absorption coefficient of water at the wavelength of 1150 nm. When a 1 mm diameter steel sphere in water contained in a rectangular glass cell with a light path length of 10 mm was heated inductively by a 760 kHz magnetic field, the absorbance images at this wavelength were acquired by using a near-infrared imaging system. The images showed that the absorbances around the sphere increased, corresponding to the heating power levels, and that a circularly symmetric distribution was formed by thermal conduction in a certain initial period and subsequently upward flow occurred by free convection. To the circularly symmetric distributions, inverse Abel transform was applied, and radial temperature distributions were reconstructed.
