Relative Humidity Period Influence on Drying Induced Stresses in Intermittent Drying of Clay

Intermittent drying is an effective strategy for improving the drying kinetics, energy consumption as well as, the quality of the dried products. The aim of this study is to investigate the effect of the period of intermittent drying on the drying kinetics and the induced stresses. To this end, a clay like material is used and by changing the air relative humidity periodically, the stresses induced were determined. Parameters variation with moisture and temperature are considered in modeling. Good agreement between experimental and simulation variables results reveals that the model developed is valid and accurate. Simulation results suggest that the drying rate should be kept at its minimum at the stage of disruption of hydraulic continuity. Due to the gradual disruption of capillary tubes in transition period, the part is affected gradually, and this necessitates the possible crack deformation points of the part to be sought simultaneously. Also, the current work studied the magnitude of each of stresses induced by non-uniform moisture distribution and stresses induced by non-uniform temperature distribution. It is shown that the thermal stresses are negligible compared to the moisture stresses and can be neglected in drying modeling.