Analysis on effect of shapes for microwave-assisted food processing of 2D samples

Abstract

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.

Present work provides guidelines on forecasting heating patterns in microwave processed foods which influence their final properties and quality. Three different cross-sections with equal area have been considered, namely, circular, square (indicated as Type1) and square inclined at an angle of 45° with horizontal plane (indicated as Type 2). Have been assumed to be exposed to lateral and radially incident microwaves. Microwave power absorption within samples have been studied using dimensionless parameters, viz. (i) Nw: represents the effect of sample size on power absorption. (ii) fp and fw: represents the effect of dielectric properties on power absorption Food materials were classified into 4 Groups with their fp, fw, as low fp and low fw (Group 1), low fp and high fw (Group 2), high fp and low fw (Group 3), high fp and high fw (Group 4), where low fp (fw) represents fp (fw)<0.3, while high fp (fw) represents fp (fw)_0.3. Power and temperature profiles have been studied in representative materials from each Group. It is found that power absorption profiles for all groups of food and for all the shapes of circular, Type 1 and Type 2 occur in three regime in increasing order of sample size, i.e (i) thin regime: characterized by uniform power absorption (ii) intermediate regime: resonances in absorbed power and (iii) thick regime: exponential attenuation of power within sample. It is also found that, in general identical areas of all the three shapes give rise to identical power absorption at any given sample dimension. Formation and location of hot-spots within material is found to be dependent on the type of incidence, sample dimensions and cross-section of material.