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Numerical modeling and validation of heat transfer in flowing fluid in a focused microwave system

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  2007 ASAE Annual Meeting  076024.(doi:10.13031/2013.23298)
Authors:   Deepti Arvind Salvi, Cristina M Sabliov, Dorin Boldor
Keywords:   ANSYS multiphysics, electromagnetics, fluid flow, heat transfer, microwave heating

In this study, a three dimensional finite element model was developed in ANSYS multi-physics 8.1 (Pittsburg, PA) by coupling electromagnetic, heat transfer, and fluid flow to simulate the temperature profile in a liquid heated in a continuous flow focused microwave system. The objectives of the study were to numerically model the heat transfer in flowing fluid in a focused microwave system and to validate the model against experimental data. Fresh water (0%) and salt water (1.5%) flowing at two different flow rates (1 and 1.6 lpm) was heated in a 915 MHz focused microwave unit at 4.5 kW incident power. The numerical temperature values were compared against experimental temperatures measured by fiber optic sensors along the axis of the applicator tube, and was found in good agreement. The average absolute error between the experimental and modeling data was approximately 3°C for the 0% salinity study and 3.9°C for 1.5% salinity study. Highest temperature (°50.8) 1.5 % salt water flowing at 1 lpm. The power loss distribution reflected in the temperature distribution; i.e. greater heat generation in the cross-section of the applicator tube resulted in higher temperature contours. Dielectric properties (mainly dielectric loss) and flow rate are important parameters which affected the microwave power absorption and hence the temperature of the material undergoing heating. The model developed in this study is a promising tool for fundamental understanding of microwave heating of flowing fluids in a focused microwave system.

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