Measurement of annular air-gap using active infrared thermography |
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| Affiliation: | 1. Radiography & Thermography Section, Non Destructive Evaluation Division, Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, Tamil Nadu, India;2. National Institute of Technology, Tiruchirappalli 620015, Tamil Nadu, India;1. Center for Interdisciplinary Research, D. Y. Patil University, Kolhapur 416006, India;2. Advanced Materials Laboratory, Department of Physics, Savitribai Phule University of Pune, India;3. Soft Matter and Molecular Biophysics Group, Applied Physics Department, University of Santiago de Compostela, Santiago de Compostela, Spain;1. Silesian University of Technology, Faculty of Electrical Engineering, ul. Akademicka 10, 44-100 Gliwice, Poland;2. Loccioni Group, Via Fiume 16, 60030 Angeli di Rosora, Ancona, Italy;1. Department of Electronics and Communication Engineering, Jansons Institute of Technology, Coimbatore, Tamil Nadu, India;2. Department of Electrical and Electronics Engineering, Coimbatore Institute of Technology, Coimbatore, Tamil Nadu, India;1. Sustainability Energy & Power Electronics Research Cluster (SuPER), Faculty of Electrical & Electronic Engineering, Universiti Malaysia Pahang, 26600 Pekan, Pahang, Malaysia;2. School of Electrical and Electronic Engineering, Universiti Sains Malaysia, Engineering Campus, 14300 Nibong Tebal, Penang, Malaysia;3. Vision Intelligent System (ViSIS), Faculty of Electrical & Electronic Engineering, Universiti Malaysia Pahang, 26600 Pekan, Pahang, Malaysia |
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| Abstract: | The paper discusses an infrared thermography (IRT) based procedure for quantification of annular air-gap in cylindrical geometries. Different annular air-gaps are simulated using aluminum hollow cylinders and solid stainless steel inserts of varying diameters. The specimens are externally heated using a hot air-gun and the temperature of the specimens are monitored during cooling using an infrared camera. The temperature decay during the cooling cycle follows an exponential profile in all the cases where the decay constant is air-gap dependent. The rate of temperature decay is fastest for the empty cases (without inserts) and lower for smaller air-gaps. The system is analyzed using a lumped system model by measuring the temperature over a time scale significantly higher than the transition time of the lumped system. It is observed that the Biot number of the system is less than unity, allowing analysis of the system in terms of a single time constant, neglecting internal temperature transients. It is observed that the time constant of temperature decay increases with decreasing annular air-gap. An empirical relation between the inverse of time constant of temperature decay and annular air-gaps is established. Using this calibration curve, unknown air-gaps up to 20 μm could be measured with good accuracy. Applications of this newly developed technique include detection of misalignment of concentric machineries and determination of fuel-to-clad gap of nuclear reactor fuels. |
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| Keywords: | Infrared thermography Annular gap measurement Lumped system Thermal decay |
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