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9 April 2007 Images processing and flow measurement applied to the thermographic analysis of heat-losses in boilers' isolation
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Infrared thermography is a non-contact evaluation technique which allows not only the registration of the temperature distribution on a surface, but also the calculation of the amount of heat flowing through it. Boilers are important for industry and the quantification of the heat losses is beneficial to avoid fuel waste. The present work suggests a methodology to calculate the thermic flow through boiler's isolation surfaces, using thermic images. With this, it is possible to find the flow by using a thermogram taking into consideration: the thermogram's range, knowing the camera's FOV, surface's emmisivity and characteristic length, object-to-camera distance, environmental temperature, and the assigned grey-level calibration curve to determined temperature range. A software tool to upload and process the information was developed. This tool can calculate the surface's average convection coefficient hc by using empiric correlations developed for common geometries and heat transfer equations to calculate the thermic flow. To test the technique functioning, the information given by the software tool was compared to the data given by the heat flow measurement thermal sensor. This comparison showed a 3% error range of relative error. The final validation was made on a waterwall-boiler's home isolated walls and the highest error obtained was close to 15%. Regardless the calibration curve was found under laboratory conditions and the empiric correlations to calculate hc are for isometric surfaces, the methodology presented a good performance. This then is a first step to quantify the global heat losses on boiler's isolation surfaces.
© (2007) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Manuel A. Hurtado, Hernán Benítez, Humberto Loaiza, Jaime Millán, Jesus A. González, and Clemente Ibarra-Castanedo "Images processing and flow measurement applied to the thermographic analysis of heat-losses in boilers' isolation", Proc. SPIE 6541, Thermosense XXIX, 65410J (9 April 2007);

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