Heating reproducibility in microwave chemistry

Statistically designed heating experiments were performed using different microwave sources to heat water under identical operating conditions. Three 2.45 GHz microwave generators were used: a) a 800 W maximum variable power source utilizing a domestic oven model magnetron; b) a 3 kW maximum non-filtered variable power commercial generator and c) a 2 kW maximum low-ripple variable power commercial generator. The same volume of water was successively heated utilizing the three different microwave sources, with equal effective power levels ranging from 190 to 380 W. The energy absorbed by the water load was evaluated by measuring the temperature increase. Preliminary results indicate that heating efficiency may vary with the type of microwave source.