Theoretical Analysis of the Tempering Phase of a Cyclic Drying Process

ABSTRACT A theoretical analysis, based on thermodynamic con-sideration of heat, work and mass distribution within the kernel, was made of the tempering phase of a cyclic drying process. The results indicate that during the tempering period only thermal effects apply; that is, only heat is exchanged between the grain and air. Curves are presented to show that the change in temperature is proportional to the change in enthalpy of the grain following redistribution of moisture within the kernel. Furthermore it is shown that when unheated air is passed through the grain dur-ing the tempering period, a higher level of energy is re-quired to sustain the drying process. Thus there is a distinct advantage in allowing the kernels to temper in quasi-stationary air.