Thermal Imaging of a Stored Grain Silo to Detect a Hot Spot
2006
Manickavasagan, A. | Jayas, D.S. | White, N.D.G. | Jian, F.
A hot spot is a localized high temperature zone in a grain bulk and normally spoilage begins in this location. Many sensors need to be installed throughout the bin to detect hot spots by measuring grain temperature. A non-contact method to detect a hot spot in a stored grain silo would be beneficial. The capability of thermal imaging to detect a hot spot in an experimental silo (galvanized steel, 1.5-m diameter and 1.5-m height) filled with barley was studied. An artificial heat source was placed at nine locations inside the grain bulk and set at four temperature levels (30°C, 40°C, 50°C, and 60°C) in each location. The outer surface of the silo wall and the top surface of the grain bulk were thermally imaged up to 48 h at each treatment (n = 3). The temperature of the top surface of the grain bulk was significantly (a = 0.05) higher (0.4°C to 2.6°C) than the atmospheric temperature after 48 h of hot spot establishment. The hot spot was detected from the thermal images of the silo wall and grain bulk (as a high temperature region) when it was located 0.3 m from the silo wall and 0.3 m below the grain surface, respectively. The hot spot was not detected on the thermal images of the silo wall when the wind velocities were 1.0, 1.5 and 2.0 m/s, and immediately after wind (n = 3). Similarly, thermal imaging did not detect the hot spot on the grain bulk when the ambient temperature was 1°C (hot spot = 30°C), and on silo wall when the ambient temperature was -8°C (hot spot = 60°C) (n = 3). The surface temperature of the grain bulk decreased with increasing moisture content. It was 25.8°C, 24.3°C, 23.4°C, 22.8°C, and 22.4°C for the grains with 8%, 12%, 16%, 20%, and 24% moisture content, respectively, when the room temperature was 26°C (n = 20). Thermal imaging can not be used as an independent method to monitor the grain temperature in a silo.
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