Determination of drying and shrinkage characteristics of porous food material in convective drying: Model development and experimental studies

Food materials are dried to enhance the shelf life, maintain nutritional value, lower packing cost, and reduce shipping cost. An innovative convective dryer is developed, which is similar to a small scale wind tunnel, to determine the drying and shrinkage characteristics of porous food material. A conjugate 3D numerical model is also developed in a commercial software COMSOL to determine the heat and moisture transfer distribution in the food material. The model considers several important phenomena like surface evaporation, internal evaporation, and shrinkage during the drying process to render high accuracy. Results show that the air temperature has significant effect on both drying and shrinkage characteristics as compared to the airflow velocity. Around 80$\% $of moisture is removed in the first 30$\% $of time and remaining 20$\% $of moisture content is removed in the last 70$\% $of time, because of high moisture gradient present in the beginning of drying. The bulk density of food increases initially, reaches a maximum value and finally decreases in the end of drying process. Numerical studies performed with this model will help to design and develop cold storage, estimate the processing time of various operations like cooling and heating.