Microwave drying of corn was investigated at selected levels of initial moisture content, absorbed power by grain, and temperature and superficial velocity of air at inlet. A surface-wave applicator was used to couple microwaves with the corn. / The drying rate curves indicated that the microwave drying of corn took place in the falling rate period. It was hypothesized that diffusion is the controlling mechanism for moisture transfer from within the kernel in microwave drying of corn. / A mathematical model was developed to describe the change in moisture content at the surface as a function of the free moisture content of corn. The diffusion model employing varying surface conditions was used to describe the microwave drying process. An Arrhenius type equation was developed to describe the relationship between the diffusion coefficient and the outlet air temperature. The diffusion coefficient values varied from 0.0008 to 0.0082 cm$ sp2$/h when constant levels of microwave power were applied continuously for drying corn. Equilibrium moisture content was determined and regression equations were developed to describe the EMC with microwave power and air velocity. / The diffusion coefficient increased with the levels of absorbed power, decreased with increasing air velocity but remained insensitive to the inlet air temperature when microwaves were applied continuously for drying corn. The increased drying rates at higher power levels reduced the drying time considerably but at the cost of energy loss through the passing air and reduced germination and bulk density of dried corn. Application of absorbed microwave power at 0.25 W/g resulted in greater than 92% germination of dried corn. Deleterious effects on product quality was observed when the applied power exceeded 0.75 W/g. / Pulsed and variable microwave power effects were investigated in order to optimize the drying process. Time for drying corn increased but the effective duration for which microwaves were applied and the energy requirement in the pulsed mode was lower compared to both continuous and variable microwave operation.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.70344 |
| Date | January 1991 |
| Creators | Shivhare, Uma Shanker |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Agricultural Engineering.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001276567, proquestno: AAINN74914, Theses scanned by UMI/ProQuest. |
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