Journal of Microwave Power and Electromagnetic Energy (JMPEE)
TITLE	The Use of Microwaves to Evaporate Liquids – The Specific Role of the Dielectric Loss Factor on Hydrodynamic Instabilities [PDF]
AUTHORS	P. Courville, G. Bertrand, M. Lallemant, A. Steinchen and D. Stuerga 1991 26 3 168-177
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Abstract A linear hydrodynamic stability analysis of polar fluids evaporated under microwave irradiation is performed for liquids with various dependence of the dielectric loss with the temperature. The analysis predicts the onset of hydrodynamic buoyancy driven instabilities for liquids with an increasing dielectric loss with temperature by a self amplification effect of the local heating. This effect is confirmed experimentally for ethanol. For liquids with decreasing dielectric loss factor with temperature the analysis shows no occurrence of buoyancy instabilities as it is confirmed by experiments on water. For high values of the microwave power absorbed, the surface itself becomes unstable by mainly two mechanisms: the Marangoni and Hickman (vapour recoil) instabilities. The coupling between these two mechanisms is studied and compared with experimental data obtained for ethanol for various values of the microwave power absorbed. For water the surface instabilities are the prevailing destabilizing mechanisms. Recent experimental verifications confirm the theoretical predictions. Key Words: Evaporation, Microwaves, Dielectric loss, Hydrodynamic instabilities.