Numerical and Experimental Analysis of Continuous Microwave Heating of Ballast Water as Preventive Treatment for Introduction of Invasive Species
D. A. Salvi, D. Boldor, C. M. Sabliov and K. A. Rusch
Ballast water transported in ocean going vessels has been demonstrated to introduce invasive aquatic species during the de-ballasting operations at ports of destinations around the world. Continuous microwave heating in focusing cavities can be applied as a treatment to ballast water to eliminate these invasive species. This paper presents the first attempt to numerically model the temperature and flow distribution in ballast water heated through a continuous focused microwave system. The model was developed by coupling the High Frequency Electromagnetic Module and FLOTRAN CFD Module in the finite element analysis software ANSYS Multiphysics™ (Pittsburg,PA), and the numerical results were validated against experimental data at different salinities using model ballast water (0 and 1.5%) heated in a 915 MHz focused microwave unit at 4.5 kW incident power. The average absolute errors between the experimental and modeling data were approximately 3 °C and 3.9 °C for the 0% and the 1.5% salinity studies, respectively. Several parameters were investigated with respect to their influence on the ballast water temperature, including water salinity (0 and 1.5%) and flow rate (1 and 1.6 lpm). The highest temperature increase (DT of 40 °C) was achieved for the 1.5%salinity water at 1 lpm,while the lowest temperature increase (DT of 6 °C) was observed for the 0% salinity water at 1.6 lpm. The power loss was numerically determined to be 0.7 kW for 0% water, respectively 2.5 kW for the 1.5% saltwater. The developed model was helpful in understanding the process of continuous microwave heating of ballast water and the effects of salt content and flow rates on the temperature profile of ballast water for temperatures below boiling. The model can be used as a tool by researchers and engineers interested in designing continuous microwave systems for heat treatment applications of ballast water.