Theoretical rationale and identification of heat and mass transfer processes in vibration dryers with IR-energy supply
The paper contains theoretical substantiation of the processes of radiation-convective heat and mass transfer between all the defining objects inside the vibration dryer with IR energy supply. The presented equations, developed on the basis of the heat and material balance, describe the basic dynamic characteristics of the drying mode for oil-bearing grain material in a continuously operating IR dryer. Since there is no exact analytic solution of the presented mathematical model shaped as a system of differential equations with partial derivatives, the authors propose an approximate solution. The latter allows identifying the dependences between the distribution of temperature and moisture content of grain and oil-containing materials along the length of the dryer for any moment of time. The numerical solution of the reduced mathematical model is possible only with the presence of certain interconnected kinetic coefficients. The kinetic coefficients can not be found experimentally by direct measurements; therefore, the article proposes a method to overcome these difficulties. The presented approximate analytical solution of the synthesized mathematical model, with the use of the method of inverse problems, has allowed determining sets of coefficients by the results of the experimental identification of dehydration. In the future, experimentally identified parametric complexes of the model can be used in the analysis of the drying process for approximate solutions or for further exact numerical solution. Experimental studies of dehydration of grain material have proved that when the power of an IR source is increased from 400 to 500 W, the time for drying from the initial moisture content of 11 % to 8.75 % decreases from 9 to 7 minutes. It is determined that the Rebinder effect characterizing the dampness and thermal properties of the material decreases with a decrease in the moisture content from 0.04 at 11 % to 0.01 at 9 %. This is interesting from the practical point of view as the obtained results and the developed mathematical model can be used for increasing the energy efficiency of the processes of thermal drying in typical facilities that prepare oil-bearing grain materials for their processing.