Two-Color Laser Induced Fluorescence Measurements of Natural Convection in a Dielectric Fluid

Two-color Planar Laser Induced Fluorescence (LIF) was used to experimentally capture the temperature profile above a horizontally oriented copper surface using PF-5060 as the dielectric working fluid. Natural convection was examined at heat fluxes ranging from 0.16 to 0.76 W/cm
²
and ambient temperatures of 20-45°C. A two-color LIF technique with an NdYag laser was used in order to implement an in situ calibration standard. Sulforhodamine 101 is used as the calibration standard as its fluorescent intensity profile is independent of fluid temperature. Rhodamine B, which has a fluorescent intensity profile that does vary with respect to temperature, is compared to that of the in situ calibration standard. Since the attenuation experienced by the fluorescing light from both of these dyes is the same as they travel through the same path to reach the camera's CCD, the ratio of these intensities produced a reliable calibration standard for experimental measurements. The entire assembly is placed in a laboratory-grade oven with a clear viewing panel for laser access during calibration and testing. Temperature uniformity of +/- 0.25°C was established in the oven during calibration, producing a repeatable and consistent calibration curve for subsequent experimental measurements. A repeatable and unobtrusive method for measuring temperature profiles have been established in the single phase. This validated technique can be carried over to future two-phase and/or heterogeneous mixture studies.