2023 Volume 43 Issue 8 Pages 21-28
This study visualized heat transfer from small heat sources to water using a near-infrared (NIR) imaging method based on the temperature-dependence of water absorption coefficient at a wavelength of 1150 nm. The NIR absorbance images of a 10-mm-thick water cell, at the bottom of which a 9 mm x 9 mm x 5 mm fin heat sink with an inductively-heated plate was placed, were acquired through a telecentric illumination and detection optics. The images showed that the temperature near the fins increased and the high-temperature region was maintained causing no significant free convection within a certain period. Then, bifurcated thermal plumes were observed, depending on the heating power. The amount of heat of water per unit of time, which corresponded to the heat release rate of the sink, was determined using the absorbance. It was found that the heat release rate was nearly constant with time and varied consistently with the heating power.
