In order to establish a technique for measuring high-speed and minute heat transfer fluctuations such as flow boiling in small diameter tubes with an infrared camera, we attempted to measure a boiling heat transfer fluctuation on a visible-light transparent heater. A visible-light transparent heater in which an ITO film with a thickness of 700 nm was formed on an infrared transparent window material (CaF2) was used as a heat transfer surface, and the boiling heat transfer of the falling droplet

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... was measured. As a result, it was possible to detect heat transfer fluctuations above 100-200 Hz in time and about 0.5 mm in space. According to the results of this experiment and the heat conduction analysis of the heat transfer surface, it was that it is possible to measure the spatio-temporal fluctuation of the heat transfer in small diameter tubes quantitatively using this measurement technique if a window material of lower thermal conductivity and an infrared camera with a high spatio-temporal resolution are used.