Microwave Ovens and Reactors - Background

This part is written as a practical tool for people interested in laboratory or industrial equipment. Exhaustive coverage of microwave oven design would require 

High-power microwaves are generated by vacuum tubes. The magnetron and klystron are the most commonly used tubes for generation of continuous waves of power suitable for microwave processing. Power is normally launched from the microwave tube into a transmission line or waveguide, where it travels to a load or termination such as an antenna or a microwave heating applicator. 

Most microwave-promoted organic synthesis has been performed in multi-mode domestic ovens. In these ovens, despite the power level which commonly fluctu- 

Another efficient way of using microwaves safely in organic synthesis is the use of solvent-free procedures (Ref [81] and Chapter 8 in this book). 

Another problem with domestic ovens is that of temperature measurement. Classical temperature sensors should be avoided because of the power levels - temperature measurements would be distorted by strong electric currents induced inside metal wires used to connect the temperature sensor. The technological solution is optical fiber thermometers [42-45], although measurements are limited to below 250 °C. For higher values, surface temperature can be estimated by use of an infrared camera or a pyrometer [46, 47]. Because of the volumic nature of microwave heating, however, surface temperatures are often less than core temperatures. 

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After some considerations relating to microwave technology, we will examine microwave ovens and reactor background. The limits of domestic ovens and temperature measurements will be analyzed, as well as design principles of microwave applicators. Next, a brief overview of laboratory, experimental and industrial equipment will be given. 

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