A NUMERICAL INVESTIGATION OF COMBINED MICROWAVE AND CONVECTIVE DRYINGOF A HYGROSCOPIC POROUS MATERIAL - A STUDY BASED ON PINE WOOD

In this paper a numerical investigation of the combined microwave and convective drying of a hygroscopic porous material is undertaken. A co mprehensive mathematical model has been developed and a numerical code known as Wood1D implemented so that the impact of dielectric heating on the overall drying kinetics can be analysed. The code, which provid es the analysis of the time evolution of moisture content, temperature , pressure and microwave power distributions, is an effective tool whi ch can be used to obtain a better understanding of the underlying phys ics of the drying process at a fundamental level. Furthermore, the sim ulations can be used to identify key model parameters so that a subseq uent sensitivity study can be carried out in order to establish the ef fects that these parameters have on the performance of combined microw ave and convective drying. Once the model has been fine tuned to the d rying engineer's specifications, the code can be used to assist with t he optimization of a given dryer design. In this work the model is tes ted and validated against experimental data for both convective drying and combined microwave and convective drying of pine wood. The drying times, drying rates and efficiencies, together with the related moist ure, temperature, pressure and power profiles will be compared and ana lysed for a number of combinations of convective and microwave energy. It is hoped that the knowledge gained from this study can be used to assist with the evaluation of the overall economic feasibility of usin g combined microwave and convective drying processes.