Thermal imaging of a stored grain silo to detect a hot spot

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 degrees C, 40 degrees C, 50 degrees C, and 60 degrees 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 (alpha = 0.05) higher (0.4 degrees C to 2.6 degrees C) than the atmospheric temperature after 48 It 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 I V (hot spot = 30 V), and on silo wall when the ambient temperature was -8 degrees C (hot spot = 60 degrees C) (n = 3). The surface temperature of the grain bulk decreased with increasing moisture content. It was 25.8 degrees C, 24.3 degrees C, 23.4 degrees C, 22.8 degrees C, and 22.4 degrees C for the grains with 8%, 12%, 16%, 20%, and 24% moisture content, respectively, when the room temperature was 26 degrees C (n = 20). Thermal imaging can not be used as an independent method to monitor the grain temperature in a silo.