A cellular dynamic mathematical model of a conveyor dryer as an object of automatic control

In the paper, based on the analysis of the technological process of fruit drying in a conveyor-type dryer, the major regime parameters, control effects of the object, control variables and disturbing factors are determined. Considering the equations of the kinetics of heat and mass transfer of the dried product, control diagrams, certain standard assumptions and initial conditions, a system of ordinary differential equations for the convective drying of fruit in a conveyor-type dryer has been developed. In the system of equations of heat and mass transfer of the process, the drying coefficient in the first and second periods and the heat transfer coefficient were determined due to identification. The solution of the problem of determining the above parameters is reduced to solving the problem of minimising the criterion for assessing the degree of the mean square deviation of the difference between the solutions of the system of experimental and heat-mass transfer differential equations of the plum drying process. During the drying of blue plums, we have obtained the following values ​​of unknown parameters: drying rate coefficient in the first period – K1=0.8309∙10-4 kg∙(m2∙s∙oC)-1; drying rate coefficient in the second period–K2=0.3413∙10-4 kg∙(m2∙s∙oC)-1 and heat transfer coefficients: α2∙ϕ2=0.0794 kW∙(kg∙oC)-1, α3∙F3=0.0245 kW∙(kg∙oC)-1 and critical moisture content of blue plums wCR=71%. The energy reduction spent on the drying process is 4%. The “cellular” dynamic characteristics of the relative humidity and temperature of the drying agent during blue plum drying, obtained as a result of the experimental and theoretical study of the conveyor drying unit, allow us to judge the 96% - 98% adequacy of the developed dynamic mathematical model. The research found that the dynamic characteristics of the residual moisture content of blue plums at the dryer outlet were 11%.