Radiometer point measure1/8/2024 ![]() The probe contains a Wheatstone bridge with two thermistors, one that is irradiated and one that is not. This method of heat flux measurement uses a probe that limits the field of view, allowing radiation measurements of relatively precise locations. ![]() Narrow Angle Radiometer Instrument Model Kaitlyn Scheib, Jennifer Spinti, Andrew Fry, Stan Harding, Igancio Preciado University of Utah, Salt Lake City, UT AugAbstract Narrow-angle radiometers based on the International Flame Research Foundation design have been used to measure the incident radiative heat flux in a coal-fired combustion furnace located at the University of Utah. Specific changes for future radiometer design are suggested. The overall uncertainty could be greatly reduced by modifying the construction of the radiometers for future tests. We present new maximum and minimum calibration curves that account for all identified uncertainties. There is also unexplained drift in the calibration curves. The major contributor to the total uncertainty is the use of the thermistor in the Wheatstone bridge. We discuss how each source of uncertainty is managed (determined to be negligible, eliminated, or included in the analysis). We have identified many sources of uncertainty in the construction, operation, and calibration of the radiometers, including transient ambient temperature effects on the Wheatstone bridge, view angle variation, lens refractive index variation, blackbody temperature, and target size. ![]() The purpose of an instrument model is to identify how the measured signal (in this case mV) is converted to the variable of interest (incident heat flux) and what possible sources of uncertainty might contribute to the calculated heat flux. Using the concept of an instrument model, we have conducted an extensive analysis of the errors associated with using this radiometer design to measure incident heat flux. The heat flux is calculated from the blackbody temperature and corrected for the view angle. This calibration produces a curve of measured voltage vs. The measured voltage difference between the two thermistors is used to determine the heat flux based on calibration curves obtained in a blackbody furnace. Narrow-angle radiometers based on the International Flame Research Foundation design have been used to measure the incident radiative heat flux in a coal-fired combustion furnace located at the University of Utah. Paper from the AFRC 2017 conference titled Narrow Angle Radiometer Instrument Model Spinti, J., Fry, A., Harding, S., Preciado, I.
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