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ISSN Online: 2377-424X

ISBN Print: 1-56032-797-9

International Heat Transfer Conference 11
August, 23-28, 1998, Kyongju, Korea

LASER-BASED TEMPERATURE MEASUREMENT AT A LIQUID SURFACE

Get access (open in a dialog) DOI: 10.1615/IHTC11.3020
pages 119-123

Resumo

This work presents a non-contact, laser-based thermoreflectance technique to measure changes in the temperature at a liquid surface. Temperature changes result in a change in the liquid index of refraction, which results in a change in the reflectivity of the liquid surface. A HeNe laser and silicon photodiodes are used to monitor the surface reflectivity. Temperature changes then can be determined from the measured reflectivity changes. In this work, pure methanol was investigated for three separate cases: heating, cooling and a cooling process followed by a heating process. The temperature change for each process was roughly 5 °C, and the test time ranged from 5 to 15 minutes. Results from the measurement are in good agreement with reference values, with a maximum uncertainty of 0.6 °C. The experimental errors arise from laser fluctuations in intensity and polarization, building vibration, liquid surface evaporation and long-term drift of the system. The presented experimental configuration does not use a lock-in amplifier, but uses instead less expensive, high precision voltmeters. The technique shows potential for a variety of applications requiring non-contact and remote monitoring of liquid surface temperature.