| All materials emit energy by virtue of electromagnetic waves due to their body temperatures and this is called radiation. Most energy emitted from a body in the range of wavelengths from 0.7 mum to 100 mum is heat and this is called infrared (IR) radiation. Infrared energy has been used in food processing frequently such as drying, baking or micronizing (cooking partially with high intensity infrared). In spite of many applications of infrared radiation in the food industry, mathematical modelling of infrared processing (micronization) has not been studied thoroughly. To understand the physical phenomena of infrared processing of agricultural products, mathematical models of IR processing using the net-radiation method which is associated with the enclosure theory were developed and validated. The models were developed for a non-moving, fixed-element configuration system and for a moving-element configuration system. The micronization experiments were conducted with yellow peas that were processed in a parallel-tray, gas-fired micronizer. The peas were tempered to 20--30% in wet basis moisture content. To validate the mathematical models, several parameters were measured. These included: moisture and temperature gradients, configuration factor from a differential control volume of peas to the emitter surface, mass flowrate, coverage factor, and surface temperatures of emitter and processed peas. The simulation results by the proposed models using the Runge-Kutta 4th order method showed good agreement with the experimental results when the emissivity of peas was assumed to be 0.9 to 0.95. Quantitative results of goodness of fit of the mathematical models are given for all the experiments conducted with the moving and the fixed element configuration. For the comparison by programming algorithm, the Euler method to solve the model equations was also used, and the simulation results were compared with the results produced by the Runge-Kutta 4th order method. This comparison showed poor fitness to the experimental results when the Euler method was used in the simulation. |
