Dynamic method for determining the permeability of a layer of high-moisture agricultural raw materials for infrared radiation

The developed dynamic method of integral heat fl ux determination is based on the single-capacity dynamic model of the thermal state of the temperature measuring transducer (TMT), experiencing thermal infl uence of the constant infrared radiation fl ux and natural convective heat exchange of the TMT surface with the surrounding air. The model can help determine the permeability of moist agricultural raw materials. The eff ectiveness of the integral heat fl ux method was tested by studying the infrared radiation permeability of a layer of purifi ed drinking water with salinity not exceeding 1 g/l and a layer of apple pulp of the Golden-Deliches variety. The response of the temperature measuring transducer to infrared radiation was experimentally determined in series when the radiation was applied directly to the TMT and through a 3 mm thick sheet of monolithic polycarbonate. A 1 to 6 mm thick layer of water and a 1 to 10 mm thick layer of apple pulp were placed on the polycarbonate sheet in 1 mm increments. As a result of approximation of the experimental data obtained, the authors determined the maximum constant temperature value of the TMT and the time constant value of the TMT transient heating process. It was found that increasing the thickness of the water layer from 1 to 6 mm was accompanied by a decrease in the layer permeability from 0.804 to 0.629 in an exponential relationship with an exponent coeffi cient of –0.736. As the thickness of the apple layer increased from 1 to 6 mm, the permeability of the wet layer decreased from 0.780 to 0.097 according to an exponential relationship with an exponent coeffi cient of –0.399. The suffi cient heating duration for the spherical TMT was about 70 s and for the blackened fl attened TMT it did not exceed 30 s. The coeffi cients of the power-law ratio can be treated as attenuation coeffi cients in the Bouguer law for thermal radiation with energy maximum at wavelength λmax equaling 0.9 to 1.1 μm. 

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