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The quasi-stationary state of microwave evaporation of a polar liquid is studied experimentally. When the energy supplied by the field to the interface is larger than the heat flux exchanged with the surroundings, the rate of evaporation is then proportional to the microwave power absorbed and can be calculated simply by dividing the power by the standard value of the latent heat of evaporation. When the field is low, the energy balance does not govern the process; the irreversibility must be taken into account.

Heat transfer between microwave heated granular material and a surrounding moving gas is both theoretically and experimentally studied. When the microwave field is homogenous, the temperature of the material can be well estimated from the gas temperature at the output and controlled through its variations. Chemical reactors heated by an inhomogeneous microwave field are also studied. Two elementary models are considered. The behavior of a long reactor, for which the travelling wave and the fluid flow have the same direction, may not be temperature stable.