PARAMETER ESTIMATION METHODOLOGY IN SELECTED MOISTURE DESORPTION MODELS

Nonlinear data analysis techniques were used to obtain parameter estimates in moisture desorption models for parboiled rice. A model for equilibrium moisture content, EMC, was combined with a thin layer model for moisture content over time and with an Arrhenius form for the drying constant to form a single model of moisture content as a function of time, temperature, relative humidity and initial moisture content.;The dry bulb temperature was maintained to within 0.2 degrees Celsius and the relative humidity to about one-half of one percent of the mean value during each test.;The data sets were studied individually, comparing models with from one to four decaying exponential terms, Page's equation, and the diffusion equation for spherical and infinite cylinder geometry. While Page's equation fits the data well, the equation is inadequate. The spherical and infinite cylinder models did not produce acceptable models. The three term exponential was able to predict the data with an error mean square of 0.3 E-6, which was believed to be the approximate accuracy of the data. In the best sets of data the four term exponential was required to explain the measured variation.;Data were selected from the complete data sets on an exponentially increasing time interval, over the first 37 hours. The parameter estimates obtained from subsets of 98 data points, following an algorithm described in this dissertation, predicted the complete data sets of over 2400 data points as well as the parameters estimated using the entire data set. These subsets, with constant temperature and relative humidity, were combined and analyzed to produce the final model covering the initial moisture content, from 0.18 to 0.30. The resulting model, with a residual mean square of 11 E-6, was found to fit the data better than a model with parameters estimated by linear techniques.;Moisture loss data were collected at twelve combinations of relative humidity and temperature ranging from 17.3 Celsius to 40.6 Celsius and from 0.24 to 0.53 relative humidity. Two samples of approximately 100 grams dry matter content and initial moisture content of between 0.50 and 0.18 dry basis were studied, simultaneously.