Abstract: The coaxial probe method is suitable for measuring the dielectric properties of high-loss materials such as fruits and vegetables. The correlation between the coaxial dielectric properties of fruits and vegetables and the dry moisture content is important for monitoring the change of water content during the processing of fruit and vegetable microwave dryers. Guiding significance. To this end, apples were used as test materials, and 500 to 8 were measured using a coaxial probe and a network analyzer. Dielectric properties of apples during microwave drying equipment in the 5 GHz frequency range.
The results show that with the increase of frequency, the dielectric constant of apple samples decreases, and the dielectric loss factor decreases first and then increases. By fitting the dielectric properties to the dry water content, the frequencies of 915 MHz and 2450 MHz are established. The equation of relationship between relative dielectric constant, dielectric loss factor and water content of apple. The research results can provide a basis for online monitoring of microwave drying moisture content by using coaxial dielectric properties.
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