Equilibrium moisture content: Use of intergranular relative air humidity sensors in silos

Abstract

Grains are hygroscopic materials and, during storage, they are subject to exchanging moisture with the environment according to temperature and relative air humidity, making it important to monitor these factors. Digital temperature and relative air humidity sensors appear as an alternative for monitoring the moisture of grain mass inside silos; they are simple to install and use. Digital sensors present outstanding precision in temperature measurements. The objective in this study was to assess the efficiency and applicability of intergranular relative air humidity sensors linked to digital temperature sensors in the thermometry system of silos storing soybeans. Two samples of soybeans were analyzed in the upper, middle and lower thirds of the silo, for grain mass temperature, intergranular relative air humidity, estimated equilibrium moisture content according to collected data, and moisture content of the sampled grains. Moisture contents obtained from sensor measurements using the hygroscopic equilibrium equation and determined using the oven method were compared. The equilibrium moisture content estimated by the data provided by the sensors did not differ by the Tukey test (p ≤ 0.05) from the moisture content determined by the oven method. Digital temperature and relative air humidity sensors have proven to be efficient, as they contribute to estimating the equilibrium moisture content with satisfactory precision.