This work presents a noncontact laser-based thermoreflectance technique to measure changes in temperature or concentration at a liquid surface. Changes in temperature and, for multi-component liquid mixtures, concentration result in a change in the liquid index of refraction, which alters the reflectivity of the liquid surface. An intensity-stabilized diode laser and silicon photodiode are used to monitor the surface reflectivity. Temperature variations in 1-propanol, methanol, ethanol, and water are measured with uncertainties of 0.5, 0.7, 0.7, and 3.7°C, respectively. For binary mixtures, the concentration of a methanol-propanol mixture is measured with an uncertainty of 0.3 percent. The experimental configuration is noninvasive, simple in design, and inexpensive. The technique can be used over a wide range of time scales, ranging from micro-seconds to minutes, and can achieve high spatial resolution by focusing the probe laser beam to a small spot size on the liquid surface. [S0022-1481(00)02803-6]
Laser-Based Measurement of Temperature or Concentration Change at Liquid Surfaces
Contributed by the Heat Transfer Division for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received by the Heat Transfer Division, July 3, 1999; revision received, Apr. 19, 2000. Associate Technical Editor: A. Majumdar.
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Fan, C. H., and Longtin, J. P. (April 19, 2000). "Laser-Based Measurement of Temperature or Concentration Change at Liquid Surfaces ." ASME. J. Heat Transfer. November 2000; 122(4): 757–762. https://doi.org/10.1115/1.1288775
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