Heat transfer in a novel microwave heating device coupled with atomization feeding

The heat transfer characteristics of the microwave heating coupled with atomization feeding were investigated using ethanol as the spray medium on a pressure swirl nozzle. The effects of spray height, flow rate and temperature on the sauter mean diameter of atomized droplets were examined. The results showed that the droplet sauter mean diameter was 12-130 ?m, which increased with the spray height and decreased with the flow rate and temperature of spray medium. Through the fitting of the experimental data, the dimensionless correlation of the droplet sauter mean diameter which was based on orifice diameter, Reynolds and Ohnesorge numbers was obtained. The calculated results were basically consistent with the experimental data within 15% error. The heat transfer characteristics of atomized droplets on high temperature surface of SiC bed heated by microwave were then investigated. The effects of spray flow rate, spray height, and spray temperature on the heat transfer characteristics were examined. The power of spray heat transfer decreased with the temperature and increased with the spray flow rate and spray height. The dimensionless correlation to describe the heat transfer characteristics of atomized droplets on the high temperature SiC surface under the microwave heating was obtained which included thermophysical properties of spray medium, spray parameters, and temperatures of the high temperature bed surface and spray medium, with the error of ?20%. These correlations can be used to predict the sauter mean diameter of the atomized droplets and the power of spray heat transfer in the microwave heating process.