AN INVESTIGATION ON THE EFFECT OF NEGLECTING COMPRESSIBLE WORK TERMS IN THE ENERGY EQUATION WHEN SIMULATING HIGH-TEMPERATURE AND PRESSURE DRYING PROCESSES

It appears traditional in the drying literature to formulate a conserv ation of enthalpy rather than a conservation of total energy when mode lling the drying process. In this work a comprehensive one-dimensional mathematical model is employed to numerically investigate the assumpt ion of neglecting terms due to the mechanical contribution of heat ari sing from compression in the energy equation. This assumption is scrut inised for the drying of cellulose materials using high temperature co nvected air and combined microwave and convected air whereby the extre me drying conditions generate high temperature and pressure gradients within the porous structure being dried. These cases should highlight the effect of the ''pressure-volume work'' terms in the energy formula tion and identify any important differences in overall drying kinetics which occur if the terms are omitted. The work seeks to identify a co nstraint, if one exists, under which an enthalpy formulation is accept able.